Atomic layer deposition method for manufacturing omnidirectional structural color multilayer structure

Abstract

A method of forming a multilayer structure of reflective omnidirectional structural color by atomic layer deposition (ALD) includes introducing at least one reflective core particle into a reaction chamber and depositing a conformal dielectric layer encapsulating the at least one reflective core particle in a dielectric layer ALD cycle. Subsequently, a conformal barrier layer encapsulating the conformal dielectric layer is deposited in a barrier layer ALD cycle, and a conformal absorber layer encapsulating the conformal barrier layer is deposited in an absorber layer ALD cycle.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to methods for manufacturing a multilayer structure for a reflective omnidirectional structural color (OSC), and in particular to methods for manufacturing a multilayer structure comprising a metal and a metal oxide layer encapsulating at least one reflective core particle, wherein at least one of the metal and the metal oxide layer is deposited by atomic layer deposition (ALD), and a barrier layer is positioned between each adjacent metal and metal oxide layer. BACKGROUND

[0002] Manufacturing OSC multilayer structures can be a complex and expensive process, in part because very strict control of layer thickness and layer quality is required. Small variations in layer thickness and subtle contamination in the layer material, i.e., including material penetration between adjacent layers, can affect the optical performance of the OSC multilayer structure.

[0003] However, the complexity and cost of conventional deposition methods for forming multilayer structures can vary depending on the desired layer thickness and the material constituting a given layer. Furthermore, conventional deposition methods limit the size and shape of the substrate or the deposition direction, leaving the sides and edges of the substrate uncoated or unevenly coated. Defects on the sides and at the edges of the substrate can result in, for example, unwanted scattering or transmission losses.

[0004] It is known to form OSC multilayer structures with ALD methods. However, conventional ALD methods are low in yield and thus too costly for manufacturing at commercial scale. SUMMARY

[0005] A first aspect includes a method of forming a reflective omnidirectional structural color multilayer structure by atomic layer deposition (ALD), the method comprising: introducing at least one reflective core particle into a reaction chamber; depositing a conformal dielectric layer encapsulating the at least one reflective core particle in a dielectric layer ALD cycle; depositing a conformal barrier layer encapsulating the conformal dielectric layer in a barrier layer ALD cycle; and depositing a conformal absorption layer encapsulating the conformal barrier layer in an absorption layer ALD cycle.

[0006] A second aspect includes the method of the first aspect, wherein the at least one reflective core particle comprises a conformal protective layer encapsulating the at least one reflective core particle.

[0007] A third aspect includes the method of the second aspect, wherein the conformal protective layer is formed by ALD, CVD, or wet chemistry.

[0008] A fourth aspect includes the method of any of the preceding aspects, further comprising depositing a conformal outer protective layer encapsulating the conformal absorption layer in an outer protective layer ALD cycle.

[0009] The fifth aspect includes the method of any of the preceding aspects, further comprising depositing a second conformal barrier layer encapsulating the conformal absorption layer in a second barrier layer ALD cycle; and depositing a second conformal dielectric layer encapsulating the second conformal barrier layer in a second dielectric layer ALD cycle.

[0010] The sixth aspect includes the method of the fifth aspect, further comprising depositing a conformal outer protective layer encapsulating the second conformal dielectric layer in an outer protective layer ALD cycle.

[0011] The seventh aspect includes the method of any of the preceding aspects, wherein the dielectric layer ALD cycle comprises, in order: supplying a first component selected from the group consisting of halides, alkyls, alkoxides, alkylamides, and carbonyls of Ti, Zn, Zr, Hf, Fe, Al, Pb, Ga, In, Si, Mg, K, and combinations thereof into the reaction chamber; purging the reaction chamber with a purge gas selected from the group consisting of nitrogen, argon, and combinations thereof; supplying a second component selected from the group consisting of O2, O3, H2O, H2O2, As2O3, As2O5, H2S, S2, Br2, HF, NH4F, SF6, and combinations thereof into the reaction chamber; and purging the reaction chamber with a purge gas selected from the group consisting of nitrogen, argon, and combinations thereof.

[0012] The eighth aspect includes the method of any of the preceding aspects, wherein the barrier layer ALD cycle comprises, in order: supplying a first component selected from the group consisting of halides, alkyls, alkoxides, alkylamides, and carbonyls of Al, Si, Mg, K, Zn, and combinations thereof into the reaction chamber; purging the reaction chamber with a purge gas selected from the group consisting of nitrogen, argon, and combinations thereof; supplying a second component selected from the group consisting of O2, O3, H2O, H2O2, Br2, HF, NH4F, and combinations thereof into the reaction chamber; and purging the reaction chamber with a purge gas selected from the group consisting of nitrogen, argon, and combinations thereof.

[0013] The ninth aspect includes the method of any of the preceding aspects, wherein the absorption layer ALD cycle comprises, in order: supplying a first component selected from the group consisting of halides, alkyls, alkoxides, alkylamides, and carbonyls of W, Cr, Ge, Ni, Pd, Ti, Si, V, Co, Mo, Nb, and combinations thereof into the reaction chamber; purging the reaction chamber with a purge gas selected from the group consisting of nitrogen, argon, and combinations thereof; supplying a second component selected from the group consisting of SiH4, Si2H6, BH3, B2H6, H2, N2, NH3, O2, O3, H2O, H2O2, and combinations thereof into the reaction chamber; and purging the reaction chamber with a purge gas selected from the group consisting of nitrogen, argon, and combinations thereof.

[0014] The tenth aspect includes the method of the fourth aspect, wherein the outer protective layer ALD cycle comprises, in order: supplying a first component selected from the group consisting of halides, alkyls, alkoxides, alkylamides, and carbonyls of Al, Si, Mg, K, Zn, and combinations thereof into the reaction chamber; purging the reaction chamber with a purge gas selected from the group consisting of nitrogen, argon, and combinations thereof; supplying a second component selected from the group consisting of O2, O3, H2O, H2O2, Br2, HF, NH4F, and combinations thereof into the reaction chamber; purging the reaction chamber with a purge gas selected from the group consisting of nitrogen, argon, and combinations thereof; supplying trimethylaluminum and water into the reaction chamber; and purging the reaction chamber with a purge gas selected from the group consisting of nitrogen, argon, and combinations thereof.

[0015] The eleventh aspect includes the method of the fifth aspect, wherein the second barrier layer ALD cycle comprises, in order: supplying a first component selected from the group consisting of halides, alkyls, alkoxides, alkylamides, and carbonyls of Al, Si, Mg, K, Zn, and combinations thereof into the reaction chamber; purging the reaction chamber with a purge gas selected from the group consisting of nitrogen, argon, and combinations thereof; supplying a second component selected from the group consisting of O2, O3, H2O, H2O2, Br2, HF, NH4F, and combinations thereof into the reaction chamber; and purging the reaction chamber with a purge gas selected from the group consisting of nitrogen, argon, and combinations thereof.

[0016] The twelfth aspect includes the method of the fifth aspect, wherein the second dielectric layer ALD cycle comprises, in order: supplying a first component selected from the group consisting of halides, alkyls, alkoxides, alkylamides, and carbonyls of Ti, Zn, Zr, Hf, Fe, Al, Pb, Ga, In, Si, Mg, K, and combinations thereof into the reaction chamber; purging the reaction chamber with a purge gas selected from the group consisting of nitrogen, argon, and combinations thereof; supplying a second component selected from the group consisting of O2, O3, H2O, H2O2, As2O3, As2O5, H2S, S2, Br2, HF, NH4F, SF6, and combinations thereof into the reaction chamber; and purging the reaction chamber with a purge gas selected from the group consisting of nitrogen, argon, and combinations thereof.

[0017] The thirteenth aspect includes the method of any of the preceding aspects, wherein, in each of the dielectric layer ALD cycle, the barrier layer ALD cycle, and the absorber layer ALD cycle individually, the reaction chamber comprises: a pressure greater than or equal to 13 pascals and less than or equal to 2666 pascals; and a temperature greater than or equal to 60 °C and less than or equal to 150 °C.

[0018] The fourteenth aspect includes the method of the fifth aspect, wherein, in each of the second barrier layer ALD cycle and the second dielectric layer ALD cycle individually, the reaction chamber comprises: a pressure greater than or equal to 13 pascals and less than or equal to 2666 pascals; and a temperature greater than or equal to 60 °C and less than or equal to 150 °C.

[0019] The fifteenth aspect includes the method of any of the preceding aspects, wherein the at least one reflective core particle is selected from Au, Cu, Al, brass, bronze, TiN, Cr, stainless steel, aluminum oxide (AI2O3), silicon dioxide (SiO2), bismuth oxychloride, a glass material, mica, and combinations thereof.

[0020] The sixteenth aspect includes the method of any of the preceding aspects, wherein the conformal dielectric layer is selected from TiO2, ZnS, ZrO2, HfO2, Fe3O4, AlAs, Fe2O3, PbS, GaAs, InAs, SiO2, MgF2, KBr, ZnO, AI2O3, and combinations thereof; the conformal barrier layer is selected from AI2O3, SiO2, MgF2, KBr, ZnO, and combinations thereof; and the conformal absorption layer is selected from W, Cr, Ge, Ni, stainless steel, Pd, Ti, Si, V, TiN, Co, Mo, Nb, iron oxides, and combinations thereof.

[0021] The seventeenth aspect includes the method of the fourth aspect, wherein the conformal outer protective layer is selected from SiO2, AI2O3, organosilanes, organophosphines, phosphates, and combinations thereof.

[0022] The eighteenth aspect includes the method of the fifth aspect, wherein the second conformal barrier layer is selected from AI2O3, SiO2, MgF2, KBr, ZnO, and combinations thereof; and the second conformal dielectric layer is selected from TiO2, ZnS, ZrO2, HfO2, Fe3O4, AlAs, Fe2O3, PbS, GaAs, InAs, SiO2, MgF2, KBr, ZnO, AI2O3, and combinations thereof.

[0023] The nineteenth aspect includes the method of the sixth aspect, wherein the conformal outer protective layer is selected from SiO2, AI2O3, organosilanes, organophosphines, phosphates, and combinations thereof.

[0024] The twentieth aspect includes the method of any of the preceding aspects, wherein the conformal dielectric layer has a thickness greater than or equal to 5 nm and less than or equal to 500 nm; the conformal barrier layer has a thickness less than or equal to 50 nm; and the conformal absorption layer has a thickness greater than or equal to 2 nm and less than or equal to 50 nm.

[0025] The twenty-first aspect includes the method of the fifth aspect, wherein the second conformal barrier layer has a thickness less than or equal to 50 nm; and the second conformal dielectric layer has a thickness greater than or equal to 5 nm and less than or equal to 500 nm. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 is a schematic cross-section of a multilayer thin film structure according to embodiments disclosed and described herein;

[0027] Figure 2 A stirred reactor for performing an ALD process is schematically depicted in accordance with the embodiments disclosed and described herein;

[0028] Figure 3A A multilayer structure with a ZnS dielectric layer extending over an Al reflective core layer used in the design of a multilayer structure is depicted;

[0029] Figure 3B A multilayer structure with a Si semiconductor absorbing layer extending over an Al reflective core layer used in the design of a multilayer structure is depicted;

[0030] Figure 3C A multilayer structure with a Fe203dielectric layer extending over an Al reflective core layer used in the design of a multilayer structure in accordance with one or more embodiments shown and described herein is depicted;

[0031] Figure 4 A multilayer structure is depicted Figures 3A-3C Reflectance characteristics of the multilayer structure shown in Example 1 on the Lab color space;

[0032] Figure 5A Hue and saturation values of the multilayer structure shown in Example 1 as a function of ZnS dielectric layer thickness are graphically depicted; Figure 3A

[0033] Hue and saturation values of the multilayer structure shown in Example 1 as a function of Si semiconductor absorbing layer thickness are graphically depicted; Figure 5B Figure 3B Hue and saturation values of the multilayer structure shown in Example 1 as a function of Fe203dielectric layer thickness are graphically depicted;

[0034] Figure 5C Figure 3C A multilayer structure is depicted

[0035] Figure 6 A multilayer structure with a dielectric layer extending over a substrate layer and exposed to electromagnetic radiation at an angle θ relative to the normal direction to the outer surface of the dielectric layer is depicted;

[0036] Figure 7A A transmission electron microscope (TEM) image of a multilayer structure in accordance with the embodiments disclosed and described herein depicting well separated metal and metal oxide layers is depicted;

[0037] Figure 7B A further magnified TEM image of a multilayer structure with a protective layer and a barrier layer in accordance with the embodiments disclosed and described herein is depicted;

[0038] Figure 7C ​​TEM image of the multilayer structure without barrier layer, where the element aluminum is highlighted to show the clear Al reflective core layer and the clear AI2O3 barrier layer;

[0039] Figure 7D TEM image of the multilayer structure without barrier layer, where the element oxygen is highlighted to show the clear SiO2protective layer, the clear TiO2dielectric layer and the clear AI2O3barrier layer;

[0040] Figure 7E TEM image of the multilayer structure without barrier layer, where the element tungsten is highlighted to show the clear W absorbing layer with smooth surface and no W penetration into the adjacent TiO2dielectric layer;

[0041] Figure 7F TEM image of the multilayer structure without barrier layer, where the element titanium is highlighted to show the clear TiO2dielectric layer with smooth surface and no TiO2penetration into the adjacent Al reflective core layer or W absorbing layer;

[0042] Figure 8B Further magnified TEM image of the multilayer structure comprising a TiO2dielectric layer encapsulating an Al reflective core layer;

[0043] Figure 8C TEM image of the multilayer structure comprising a TiO2dielectric layer encapsulating an Al reflective core layer and a W absorbing layer encapsulating the TiO2dielectric layer, without barrier layer between the W absorbing layer and the TiO2dielectric layer;

[0044] Figure 8D Further magnified TEM image of the multilayer structure without barrier layer and indicating the area to be analyzed for elemental analysis by energy dispersive X-ray;

[0045] Figure 8E TEM image of the multilayer structure without barrier layer, where the element aluminum is highlighted;

[0046] Figure 8F TEM image of the multilayer structure without barrier layer, where the element oxygen is highlighted;

[0047] Figure 8G TEM image of the multilayer structure without barrier layer, where the element tungsten is highlighted, where tungsten is found dispersed throughout the TiO2layer;

[0048] Figure 8H TEM image of the multilayer structure without barrier layer, where the element carbon is highlighted;

[0049] Figure 8I TEM image of the multilayer structure without barrier layer, where the element titanium is highlighted;

[0050] Figure 8ATEM image of a multilayer structure comprising a Ti02dielectric layer encapsulating an Al reflective core layer;

[0051] Figure 9 Image showing that a structure with a barrier layer has enhanced pigment colorimetry over an OSC multilayer structure without a barrier layer;

[0052] Figure 10A Graph of reflectivity versus electromagnetic radiation wavelength showing the effect of tungsten absorbing layer thickness; and

[0053] Figure 10B Graph of reflectivity versus electromagnetic radiation wavelength showing the effect of Ti02dielectric layer thickness. DETAILED DESCRIPTION

[0054] The present disclosure relates to atomic layer deposition (ALD) of multilayer structures comprising metals and metal oxides on reflective substrates for optical applications. At least one of the metals and metal oxides is deposited by ALD, and a barrier layer is positioned between each adjacent metal and metal oxide layer.

[0055] It is known to form omnidirectional structural color (OSC) multilayer structures by depositing metals or metal oxides directly to reflective materials and other metal and / or metal oxide layers using ALD methods. However, to date, ALD deposition has been expensive and time consuming. In particular, conventionally utilized ALD methods have low throughput and are cost prohibitive for manufacturing at commercial scales. Furthermore, when attempting to increase production throughput, cross-layer material penetration is observed. Thus, a method of forming OSC multilayer structures that enables conformal coating, ultra-thin layer deposition with nanometer-scale precision, extremely low cross-layer material penetration, and reduced manufacturing time is desirable.

[0056] For example, ALD deposits materials at essentially an atomic level, so depositing thick layers, e.g., layers having a thickness greater than 500 nm, using an ALD process can take a significant amount of time. Thus, for depositing each layer in a multilayer structure, ALD is generally not preferred. Due to cost and time constraints, ALD has traditionally been dedicated to depositing very thin layers.

[0057] Furthermore, when attempting to increase production throughput, it is noted that various metal and / or metal oxide layers interpenetrate and form mixed layers, which can affect the optical properties of the OSC multilayer structure. This interpenetration is believed to occur due to the high porosity of the dielectric layers. That is, when a metal absorbing layer is deposited by ALD, the high porosity of the dielectric layers allows the metal to soak into the pores of the adjacent dielectric layer that interpenetrate the dielectric layer and result in mixed layers of metals and metal oxides. Such mixed layers can significantly affect the overall optical properties of the multilayer structure due to the reduced reflection and transmission properties of the dielectric layers.

[0058] However, as mentioned above, the preparation of OSC multilayer structures requires very strict control of layer thickness and layer quality, and small variations in thickness and material can affect the optical performance of the OSC multilayer structure.

[0059] ALD is a technique that is good at depositing layers with nanometer scale thickness directly on a reflective core layer. Furthermore, ALD can deposit layers that conform to the size and shape of the substrate on which it is deposited, such that the deposited layer encapsulates the substrate (i.e., is present on all sides of the substrate). That is, the substrate and resulting multilayer structure can have an asymmetric and non-uniform shape.

[0060] Accordingly, disclosed herein are ALD methods for forming multilayer structures, wherein the ALD processes coating the layers of the multilayer structure can be performed in the same chamber. This means that downtime for removing particles and loading them into another chamber can be avoided. The processes disclosed herein allow for safe and efficient commercial scale-up of ALD processes that have previously only been performed on a bench scale producing grams of material.

[0061] Furthermore, the ALD methods disclosed and described herein can be used to apply thin (nanometer scale) metal and metal oxide layers to reflective substrates, as well as to apply metal and metal oxide layers to other metal and metal oxide layers. Furthermore, thin barrier layers can be deposited between adjacent metal and metal oxide layers. The barrier layers prevent the metal from impregnating into the pores of the dielectric layer and forming a mixed layer. With the barrier layers, all adjacent metal and metal oxide layers are well separated, and their optical properties are also well predicted by simulation. Furthermore, in embodiments, the barrier layers are thin layers and are made of a material that does not affect the optical properties of the multilayer structure.

[0062] The multilayer structures manufactured by the methods disclosed herein can be used as pigments in compositions (e.g., paint compositions), continuous thin films on structures, and the like.

[0063] Embodiments of the multilayer structures described herein can be used to omnidirectionally reflect wavelengths of visible light over a range of viewing incidence angles.

[0064] Furthermore, in embodiments, the OSC multilayer structure can reflect a single narrowband of electromagnetic radiation in the visible spectrum when exposed to broadband electromagnetic radiation. The single visible light narrowband includes a color shift measured in the Lab color space of less than 30° when viewed at an angle of 0° to 45° relative to the normal direction of the outer surface of the multilayer film. Such a hue shift is small or not noticeable. For example, embodiments of the above-described multilayer structure 100 can have a hue shift in the Lab color space of less than 30°, such as less than 25°, less than 20°, less than 15°, or less than 10° when viewed at an angle of 0° to 45°.

[0065] It should be understood that the terms "electromagnetic wave," "electromagnetic radiation," and "light" as used herein can be used interchangeably to refer to light of various wavelengths incident on the multilayer structure, and such light can have wavelengths in the ultraviolet (UV), infrared (IR), and visible light portions of the electromagnetic spectrum.

[0066] As used herein, "substrate" refers to the core layer and core particle. It should be understood that the terms "substrate," "core layer," and "core particle" as used herein can be used interchangeably to refer to the surface on which the layer material is deposited. The "substrate" can have any shape, including but not limited to, a sheet shape, a spherical shape, an oval shape, and the like.

[0067] As used herein, "absorbing layer" includes metallic absorbing layers and non-metallic absorbing layers.

[0068] As used herein, "dielectric layer" includes metallic oxide dielectric layers and non-metallic oxide dielectric layers.

[0069] A multilayer structure will now be described. Referring now to Figure 1 A multilayer structure 100 according to the embodiments disclosed and described herein includes a reflective core particle 110, a conformal protective layer 111 encapsulating the reflective core particle 110, a conformal dielectric layer 120 encapsulating the conformal protective layer 111, a conformal barrier layer 121 encapsulating the conformal dielectric layer 120, a conformal absorbing layer 130 encapsulating the conformal barrier layer 121, a second conformal barrier layer 131 encapsulating the conformal absorbing layer 130, a second conformal dielectric layer 140 encapsulating the second conformal barrier layer 131, and a conformal outer protective layer 141 encapsulating the second conformal dielectric layer 140. As used herein, "conformal" is used to mean that the layer conforms to the size and shape of the layer on which it is deposited, and encapsulates the layer on which it is deposited (i.e., is present on all sides of the layer on which it is deposited), and conforms to the contours of the layer on which it is deposited. Although Figure 1 A rectangular structure is shown, but this is for illustrative purposes only, and the multilayer structure will generally have an asymmetric and non-uniform shape. In embodiments, the multilayer structure can be spherical or oval.

[0070] In one or more embodiments, the multilayer structure 100 can include fewer layers than those depicted in Figure 1 For example, in embodiments, the multilayer structure 100 includes a substrate 110, a first conformal protective layer 111 encapsulating the substrate 110, a conformal dielectric layer 120 encapsulating the first conformal protective layer 111, a conformal barrier layer 121 encapsulating the conformal dielectric layer 120, a conformal absorbing layer 130 encapsulating the conformal barrier layer 121, a second conformal barrier layer 131 encapsulating the conformal absorbing layer 130, and a second conformal dielectric layer 140 encapsulating the second conformal barrier layer 131.

[0071] In one or more embodiments, the multilayer structure 100 includes a substrate 110, a conformal dielectric layer 120 encapsulating the substrate 110, a conformal barrier layer 121 encapsulating the conformal dielectric layer 120, a conformal absorber layer 130 encapsulating the conformal barrier layer 121, a second conformal barrier layer 131 encapsulating the conformal absorber layer 130, and a second conformal dielectric layer 140 encapsulating the second conformal barrier layer 131. An optional conformal outer protective layer 141 can encapsulate the second conformal dielectric layer 140.

[0072] In embodiments, the multilayer structure 100 includes a substrate 110, a conformal dielectric layer 120 encapsulating the substrate 110, a conformal barrier layer 121 encapsulating the conformal dielectric layer 120, and a conformal absorber layer 130 encapsulating the conformal barrier layer 121. An optional conformal outer protective layer can encapsulate the conformal absorber layer 130.

[0073] In one or more embodiments, the multilayer structure 100 includes a substrate 110, a first conformal protective layer 111 encapsulating the substrate 110, a conformal dielectric layer 120 encapsulating the first conformal protective layer 111, a conformal barrier layer 121 encapsulating the conformal dielectric layer 120, and a conformal absorber layer 130 encapsulating the conformal barrier layer 121. A second conformal barrier layer 131 can optionally encapsulate the conformal absorber layer 130.

[0074] It is understood that embodiments can also include multilayer structures having a conformal absorber layer encapsulating a substrate and a conformal dielectric layer encapsulating the conformal absorber layer. The multilayer structure can also include an optional conformal protective layer and optional barrier positioned between the conformal absorber layer and the substrate, an optional conformal barrier positioned between the conformal dielectric layer and the conformal absorber layer, and an optional outer protective layer encapsulating the conformal dielectric layer.

[0075] The ALD methods disclosed herein for fabricating multilayer structures will now be generally described. ALD of each layer (dielectric layer, barrier layer, absorber layer, protective layer, and outer protective layer) is performed by coating the substrate in a stirred reactor with the appropriate precursor compound at an appropriate temperature, typically ranging from 60 °C to 150 °C. The precursors are supplied in the gas phase, which can be a gas at ambient temperature, or vaporized and delivered through a carrier gas such as nitrogen and argon. It is understood that the terms “precursor,” “precursor compound,” and “compound” as used herein can be used interchangeably to refer to the various precursors supplied to form the dielectric layer, barrier layer, absorber layer, protective layer, and outer protective layer of the multilayer structure.

[0076] Reference will now be made to Figure 2According to one or more embodiments, a stirred reactor 600 for depositing a layer by ALD includes a reaction chamber 610 in which ALD is performed. The reaction chamber 610 can be equipped with a heater (not shown). The reaction chamber 610 also includes an inlet for a first precursor gas 620, an inlet for a second precursor gas 622, and an inlet for a purge gas 624. It should be understood that in embodiments there can be a single inlet in the chamber 610 for the first precursor gas 620, the second precursor gas 622, and the purge gas 624, while in other embodiments there can be two or three different inlets in the chamber 610 for the first precursor gas 620, the second precursor gas 622, and the purge gas 624. It should also be understood that if more than two precursors are needed, additional inlets can be provided. For the sake of clarity, FIG. 5 depicts an embodiment with three inlets for the first precursor gas 620, the second precursor gas 622, and the purge gas 624. The chamber 610 can also include a gas outlet 630 for releasing gas from the chamber 610. According to one or more embodiments, the gas outlet 630 can include a pump (not shown) to facilitate the release of gas from the chamber 610, and the gas outlet 630 can include a filter 632 that prevents particles from exiting the chamber 610 via the gas outlet 630. Also present within the chamber 610 is a stirring device 640 to stir the particles during the ALD process. A chamber vibrator 650 is used to vibrate the chamber 610 during the ALD process, which helps to ensure uniform deposition.

[0077] During the ALD process, and still referring to FIG. 5, the first precursor gas 620 is introduced into the chamber 610. The first precursor gas 620 is introduced into the chamber 610 for a period of time sufficient to allow the first precursor gas 620 to coat the particles. The first precursor gas 620 is then purged from the chamber 610. The second precursor gas 622 is then introduced into the chamber 610. The second precursor gas 622 is introduced into the chamber 610 for a period of time sufficient to allow the second precursor gas 622 to coat the particles. The second precursor gas 622 is then purged from the chamber 610. The process is then repeated. Figure 2Multiple layers can be coated to a substrate (e.g., multiple reflective core layers 110) in a stirred reactor 600. The substrate is introduced into the reaction chamber 610 and mixed with the stirring device 640. Chamber shaker 650 can be used to avoid powder agglomeration and enhance coating uniformity, meaning that this type of stirred reactor does not require large flow rates of fluidization gas. To perform ALD on each layer (e.g., conformal dielectric layer 120 and conformal metal absorber layer 130), the previously deposited layer (or substrate) is coated with the corresponding precursor at a deposition temperature. In embodiments, the deposition temperature can be greater than or equal to 60 °C and less than or equal to 150 °C, such as greater than or equal to 80 °C and less than or equal to 150 °C, greater than or equal to 90 °C and less than or equal to 150 °C, greater than or equal to 100 °C and less than or equal to 150 °C, greater than or equal to 110 °C and less than or equal to 150 °C, greater than or equal to 120 °C and less than or equal to 150 °C, greater than or equal to 130 °C and less than or equal to 150 °C, greater than or equal to 60 °C and less than or equal to 130 °C, greater than or equal to 80 °C and less than or equal to 130 °C, greater than or equal to 90 °C and less than or equal to 130 °C, greater than or equal to 100 °C and less than or equal to 130 °C, greater than or equal to 110 °C and less than or equal to 130 °C, greater than or equal to 120 °C and less than or equal to 130 °C, greater than or equal to 60 °C and less than or equal to 120 °C, greater than or equal to 80 °C and less than or equal to 120 °C, greater than or equal to 90 °C and less than or equal to 120 °C, greater than or equal to 100 °C and less than or equal to 120 °C, greater than or equal to 110 °C and less than or equal to 120 °C, greater than or equal to 60 °C and less than or equal to 110 °C, greater than or equal to 80 °C and less than or equal to 110 °C, greater than or equal to 90 °C and less than or equal to 110 °C, greater than or equal to 100 °C and less than or equal to 110 °C, greater than or equal to 60 °C and less than or equal to 100 °C, greater than or equal to 80 °C and less than or equal to 100 °C, greater than or equal to 90 °C and less than or equal to 100 °C, greater than or equal to 60 °C and less than or equal to 90 °C, greater than or equal to 80 °C and less than or equal to 90 °C, or greater than or equal to 60 °C and less than or equal to 80 °C. The precursors can be supplied in the gas phase, or vaporized and delivered by a carrier gas, such as nitrogen and argon.

[0078] According to embodiments, the dielectric and barrier layers are deposited by a reaction between a metal-containing compound and an oxygen-containing material. In embodiments, the metal-containing compound includes halides, alkyls, alkoxides, alkyl amides, and carbonyls. For example, to form a conformal dielectric layer of Ti02on a substrate, titanium tetrachloride (TiCl4) can be selected as a precursor according to embodiments, and to form a conformal barrier layer of AI2O3, trimethylaluminum (TMA) can be selected as a precursor according to embodiments. In embodiments, the oxygen-containing material includes oxygen (02), ozone (03), water (H2O), and hydrogen peroxide (H2O2). The metal-containing compound and the oxygen-containing compound are supplied as first precursors in stoichiometric ratios, and the amount of the first precursors is estimated according to the surface area of the uncoated particles to improve the precursor utilization.

[0079] In one or more embodiments, the conformal metal absorption layer is deposited by a reaction between a metal-containing compound and one or more reducing agents. The metal- containing compound according to embodiments includes halides, alkyls, alkoxides, alkyl amides, and carbonyls. For example, to deposit a W metal absorber, tungsten hexafluoride (WF6) is selected as a metal-containing compound. The reducing agents of embodiments include silane (SiH4), disilane (Si2H6), borane (BH3), diborane (B2H6), and hydrogen (H2). The metal- containing compound and the reducing agent are supplied as second precursors in stoichiometric ratios, and the amount of the second precursors is estimated according to the surface area of the uncoated particles to improve the precursor utilization.

[0080] The steps of forming a multilayer structure using the stirred reactor 600 shown in FIG. 6 will now be provided. Figure 2 The steps of forming a multilayer structure using the stirred reactor 600 shown in FIG. 6 will now be provided.

[0081] In a first step, and according to embodiments, the substrate particles (e.g., reflective core layer particles) are introduced into the stirred reactor 600, and the chamber 610 is evacuated and heated to a deposition temperature, which is typically 60 °C to 150 °C, as described above. This temperature is maintained for 1 hour to 4 hours, such as 1 hour to 3 hours or 2 hours to 4 hours, to confirm its stability.

[0082] In a second step, and according to embodiments, a first precursor gas 620 is introduced into the reaction chamber 610 through the inlet for a duration of 1 second to 60 seconds. This first precursor gas 620 dosing step is monitored by a pressure sensor. The substrate is mixed with the first precursor gas 620 at a target pressure to allow the first precursor gas 620 to be sufficiently absorbed onto active sites of the substrate.

[0083] In a third step, and according to embodiments, the chamber 610 is purged by introducing a purge gas 624 through the inlet into the chamber 610 to remove excess first precursor and byproducts present in the chamber 610 after the second step. The purge gas 624 is introduced into the chamber 610 for a duration of 1 second to 60 seconds, followed by a vacuum pull in the chamber 610. The purge gas 624 is a dry inert gas, such as nitrogen, argon, or a combination thereof. The third step can be repeated multiple times to confirm that excess first precursor will not affect the next steps.

[0084] In a fourth step, and according to embodiments, the second precursor gas 622 is introduced into the chamber 610 through the inlet for a duration of 1 second to 60 seconds. The second precursor gas 622 dosing step is monitored by a pressure sensor. The substrate, now coated with a conformal dielectric layer, is mixed with the second precursor at a target pressure to allow sufficient reaction between the metal-containing compounds of the second precursor gas 622 and the reducing agent.

[0085] In a fifth step, and according to embodiments, the chamber 610 is again purged by introducing a purge gas 624 through the inlet into the chamber 610 to remove excess precursor and byproducts introduced into the chamber 610 by the fourth step. The purge gas 624 is introduced into the chamber 610 for a duration of 1 second to 60 seconds, followed by a vacuum pull in the chamber 610. This step can be repeated multiple times to confirm that excess precursor will not affect the next steps.

[0086] It is understood that, in embodiments, the metal absorber layer can be deposited directly on the substrate by introducing the second precursor gas in step two, and the dielectric layer can be deposited on the absorber layer by introducing the first precursor in step four.

[0087] In the above-mentioned second and fourth steps, each individual precursor dosing step is monitored by a pressure sensor.The pressure in the reaction chamber 610 can be greater than or equal to 13 Pascal (Pa) and less than or equal to 2666 Pa, such as greater than or equal to 67 Pa and less than or equal to 2666 Pa, greater than or equal to 133 Pa and less than or equal to 2666 Pa, greater than or equal to 667 Pa and less than or equal to 2666 Pa, greater than or equal to 1333 Pa and less than or equal to 2666 Pa, greater than or equal to 2000 Pa and less than or equal to 2666 Pa, greater than or equal to 13 Pa and less than or equal to 2333 Pa, greater than or equal to 67 Pa and less than or equal to 2333 Pa, greater than or equal to 133 Pa and less than or equal to 2333 Pa, greater than or equal to 667 Pa and less than or equal to 2333 Pa, greater than or equal to 1333 Pa and less than or equal to 2333 Pa, greater than or equal to 2000 Pa and less than or equal to 2333 Pa, greater than or equal to 13 Pa and less than or equal to 2000 Pa, greater than or equal to 67 Pa and less than or equal to 2000 Pa, greater than or equal to 133 Pa and less than or equal to 2000 Pa, greater than or equal to 667 Pa and less than or equal to 2000 Pa, greater than or equal to 1333 Pa and less than or equal to 2000 Pa, greater than or equal to 13 Pa and less than or equal to 1667 Pa, greater than or equal to 67 Pa and less than or equal to 1667 Pa, greater than or equal to 133 Pa and less than or equal to 1667 Pa, greater than or equal to 667 Pa and less than or equal to 1667 Pa, greater than or equal to 1333 Pa and less than or equal to 1667 Pa, greater than or equal to 13 Pa and less than or equal to 1333 Pa, greater than or equal to 67 Pa and less than or equal to 1333 Pa, greater than or equal to 333 Pa and less than or equal to 1333 Pa, greater than or equal to 1000 Pa and less than or equal to 1333 Pa, greater than or equal to 13 Pa and less than or equal to 1000 Pa, greater than or equal to 67 Pa and less than or equal to 1000 Pa, greater than or equal to 333 Pa and less than or equal to 1000 Pa, greater than or equal to 667 Pa and less than or equal to 1000 Pa, greater than or equal to 13 Pa and less than or equal to 667 Pa, greater than or equal to 67 Pa and less than or equal to 667 Pa, greater than or equal to 133 Pa and less than or equal to 667 Pa, greater than or equal to 333 Pa and less than or equal to 667 Pa, greater than or equal to 13 Pa and less than or equal to 333 Pa, greater than or equal to 67 Pa and less than or equal to 333 Pa, greater than or equal to 133 Pa and less than or equal to 333 Pa, greater than or equal to 13 Pa and less than or equal to 133 Pa, greater than or equal to 67 Pa and less than or equal to 133 Pa, or greater than or equal to 13 Pa and less than or equal to 67 Pa.

[0088] The second through fifth steps of the ALD cycle can each be repeated until a desired layer thickness is achieved. For example, to form a thick dielectric layer, the second step can be repeated before the third step is performed, or the second and third steps can be repeated consecutively before the fourth step is performed. Similarly, to form a thick absorbing layer, the fourth step can be repeated before the fifth step is performed, or the fourth and fifth steps can be repeated consecutively before proceeding. With the above steps of the ALD process, each layer of the multilayer structure can be performed in the same chamber in which the previous layer was deposited by ALD. Depositing different layers using the same chamber reduces the downtime required in traditional processes in which the substrate is removed from the chamber after depositing a first layer with a first precursor and loaded into a second chamber to deposit a second layer with a second precursor.

[0089] Details of the ALD method for fabricating each layer of the multilayer structure, including the dielectric layer, the barrier layer, the absorbing layer, the protective layer, and the outer protective layer, will now be further described.

[0090] In embodiments, the method of forming a multilayer structure of a reflective omni-directional structural color by ALD includes introducing at least one reflective core particle into a reaction chamber; depositing a conformal dielectric layer encapsulating the at least one reflective core particle in a dielectric layer ALD cycle; depositing a conformal barrier layer encapsulating the conformal dielectric layer in a barrier layer ALD cycle; and depositing a conformal absorbing layer encapsulating the conformal barrier layer in an absorbing layer ALD cycle. In embodiments, the at least one reflective core particle can include a conformal protective layer encapsulating the at least one reflective core particle. In embodiments, the conformal protective layer can be formed by ALD, CVD, or wet chemistry. The method can further include depositing a conformal outer protective layer encapsulating the conformal absorbing layer in an outer protective layer ALD cycle.

[0091] In embodiments, the method can further include depositing a second conformal barrier layer encapsulating the conformal absorbing layer in a second barrier layer ALD cycle; and depositing a second conformal dielectric layer encapsulating the second conformal barrier layer in a second dielectric layer ALD cycle. The method can further include depositing a conformal outer protective layer encapsulating the second conformal dielectric layer in an outer protective layer ALD cycle.

[0092] Each of the foregoing ALD cycles will now be described.

[0093] In embodiments, the dielectric layer ALD cycle includes sequentially supplying a dielectric layer precursor comprising two components into the reaction chamber. In embodiments, the first component is selected from the group consisting of halides, alkyls, alkoxides, alkylamides, and carbonyls of Ti, Zn, Zr, Hf, Fe, Al, Pb, Ga, In, Si, Mg, K, and combinations thereof. The reaction chamber is then purged with a purge gas selected from the group consisting of nitrogen, argon, and combinations thereof. A second component selected from the group consisting of O2, O3, H2O, H2O2, As2O3, As2O5, H2S, S2, Br2, HF, NH4F, SF6, and combinations thereof is introduced into the reaction chamber. Finally, the reaction chamber is purged with a purge gas selected from the group consisting of nitrogen, argon, and combinations thereof.

[0094] In embodiments, the barrier layer ALD cycle includes sequentially supplying a barrier layer precursor comprising two components into the reaction chamber. In embodiments, the first component is selected from the group consisting of halides, alkyls, alkoxides, alkylamides, and carbonyls of Al, Si, Mg, K, Zn, and combinations thereof. The reaction chamber is then purged with a purge gas selected from the group consisting of nitrogen, argon, and combinations thereof. A second component selected from the group consisting of O2, O3, H2O, H2O2, Br2, HF, NH4F, and combinations thereof is introduced into the reaction chamber. Finally, the reaction chamber is purged with a purge gas selected from the group consisting of nitrogen, argon, and combinations thereof.

[0095] In embodiments, the absorption layer ALD cycle includes sequentially supplying an absorption layer precursor comprising two components into the reaction chamber. In embodiments, the first component is selected from the group consisting of halides, alkyls, alkoxides, alkylamides, and carbonyls of W, Cr, Ge, Ni, Pd, Ti, Si, V, Co, Mo, Nb, and combinations thereof. The reaction chamber is then purged with a purge gas selected from the group consisting of nitrogen, argon, and combinations thereof. A second component selected from the group consisting of SiH4, Si2H6, BH3, B2H6, H2, N2, NH3, O2, O3, H2O, H2O2, and combinations thereof is introduced into the reaction chamber. Finally, the reaction chamber is purged with a purge gas selected from the group consisting of nitrogen, argon, and combinations thereof.

[0096] In embodiments, the second barrier layer ALD cycle includes sequentially supplying a second barrier layer precursor comprising two components into the reaction chamber. In embodiments, the first component is selected from the group consisting of halides, alkyls, alkoxides, alkylamides, and carbonyls of Al, Si, Mg, K, Zn, and combinations thereof. The reaction chamber is then purged with a purge gas selected from the group consisting of nitrogen, argon, and combinations thereof. A second component selected from the group consisting of O2, O3, H2O, H2O2, Br2, HF, NH4F, and combinations thereof is introduced into the reaction chamber. Finally, the reaction chamber is purged with a purge gas selected from the group consisting of nitrogen, argon, and combinations thereof.

[0097] In embodiments, the second dielectric layer ALD cycle includes sequentially supplying a second dielectric layer precursor comprising two components into the reaction chamber. In embodiments, the first component is selected from the group consisting of halides, alkyls, alkoxides, alkylamides, and carbonyls of Ti, Zn, Zr, Hf, Fe, Al, Pb, Ga, In, Si, Mg, K, and combinations thereof. The reaction chamber is then purged with a purge gas selected from the group consisting of nitrogen, argon, and combinations thereof. A second component selected from the group consisting of O2, O3, H2O, H2O2, As2O3, As2O5, H2S, S2, Br2, HF, NH4F, SF6, and combinations thereof is introduced into the reaction chamber. Finally, the reaction chamber is purged with a purge gas selected from the group consisting of nitrogen, argon, and combinations thereof.

[0098] In embodiments, the outer protective layer ALD cycle includes sequentially supplying an outer protective layer precursor comprising two components into the reaction chamber. In embodiments, the first component is selected from the group consisting of halides, alkyls, alkoxides, alkylamides, and carbonyls of Al, Si, Mg, K, Zn, and combinations thereof. The reaction chamber is then purged with a purge gas selected from the group consisting of nitrogen, argon, and combinations thereof. A second component selected from the group consisting of O2, O3, H2O, H2O2, Br2, HF, NH4F, and combinations thereof is introduced into the reaction chamber. Finally, the reaction chamber is purged with a purge gas selected from the group consisting of nitrogen, argon, and combinations thereof.

[0099] The multilayer structure is coated with an outer protective layer of AI2O3, where trimethylaluminum (TMA) and water are used as precursors to form the protective layer in the reactor.

[0100] The multilayer structure formed by utilizing the above ALD method will now be described.

[0101] In embodiments, the at least one reflective core particle 110 can be made of at least one of "gray metal" materials, such as Al, Ag, Pt, Sn; at least one of "color metal" materials, such as Au, Cu, brass, bronze, TiN, Cr, stainless steel, or combinations thereof. In one or more embodiments, the at least one reflective core particle 110 can be selected from the group consisting of Au, Cu, Al, brass, bronze, TiN, Cr, stainless steel, aluminum oxide (AI2O3), silicon dioxide (SiO2), bismuth oxychloride, glass material, mica, and combinations thereof. The substrate 110 can have a plate-like shape, or can be spherical or ovoid as described above.

[0102] In embodiments, the conformal dielectric layer 120 can be selected from the group consisting of Ti02, ZnS, Zr02, Hf02, Fe304, AlAs, Fe203, PbS, GaAs, InAs, Si02, MgF2, KBr, ZnO, Al203, and combinations thereof. In embodiments, the conformal dielectric layer 120 can be a high refractive index material such as Ti02in rutile or anatase phase, a low refractive index material such as Si02, or Fe203.

[0103] In embodiments, the conformal absorbing layer 130 can be selected from the group consisting of W, Cr, Ge, Ni, stainless steel, Pd, Ti, Si, V, TiN, Co, Mo, Nb, iron oxides, and combinations thereof.

[0104] In embodiments, the multilayer structure includes a protective layer 111 encapsulating the substrate 110, the conformal protective layer 111 can be a dense layer selected from the group consisting of Si02, Al203, Fe203, and combinations thereof. The protective layer 111 can also be deposited by chemical vapor deposition (CVD), physical vapor deposition (PVD), or wet chemical (WC) methods depending on the thickness and material of the protective layer.

[0105] In embodiments, the multilayer structure further includes a conformal barrier layer 121 positioned between the conformal dielectric layer 120 and the conformal absorbing layer 130, the conformal barrier layer 121 can be selected from the group consisting of Al203, Si02, MgF2, KBr, ZnO, and combinations thereof.

[0106] In embodiments, the multilayer structure can be encapsulated by an optional conformal outer protective layer encapsulating the conformal absorbing layer 130, the optional conformal outer protective layer can be selected from the group consisting of Si02, Al203, organosilanes, organophosphines, phosphates, and combinations thereof.

[0107] In particular, in embodiments, the multilayer structure 100 can include at least one reflective core particle 110 comprising Al, a conformal dielectric layer 120 comprising Ti02or Fe203, a conformal barrier layer 121 comprising Al203, and a conformal absorbing layer 130 comprising W.

[0108] Referring again to Figure 1The multilayer structure 100 according to the embodiments disclosed and described herein includes a substrate 110, a conformal dielectric layer 120 encapsulating the substrate 110, a conformal absorbing layer 130 encapsulating the conformal dielectric layer 120, and a second conformal dielectric layer 140 encapsulating the conformal absorbing layer 130. The multilayer structure 100 disclosed and described herein consists of four“optical layers” (substrate 110, dielectric layer 120, absorbing layer 130, and second dielectric layer). These four optical layers affect the optical properties of the multilayer structure 100. The term“optical layer” as used herein does not include barrier, protective, and outer protective layers that do not affect the optical properties of the multilayer structure.

[0109] In embodiments where the multilayer structure 100 further includes a second conformal dielectric layer 140, the second conformal dielectric layer 140 can be selected from the group consisting of Ti02, ZnS, Zr02, Hf02, Fe304, AlAs, Fe203, PbS, GaAs, InAs, Si02, MgF2, KBr, ZnO, AI2O3, and combinations thereof. In embodiments, the second conformal dielectric layer 140 can be a high refractive index material such as Ti02in rutile or anatase phase, a low refractive index material such as Si02, or Fe203.

[0110] In embodiments, the multilayer structure further includes a second conformal barrier layer 131 positioned between the conformal absorbing layer 130 and the second conformal dielectric layer 140, which can be selected from the group consisting of AI2O3, Si02, MgF2, KBr, ZnO, and combinations thereof.

[0111] In embodiments, the multilayer structure can be encapsulated by a conformal outer protective layer 141 encapsulating the second conformal dielectric layer 140, which can be selected from the group consisting of Si02, AI2O3, organosilanes, organophosphines, phosphates, and combinations thereof.

[0112] Specifically, in embodiments, the multilayer structure can include at least one reflective core particle 110 comprising Al, a conformal protective layer 111 comprising Si02or AI2O3, a conformal dielectric layer 120 comprising Ti02or Fe203, a conformal barrier layer 121 comprising AI2O3, a conformal absorbing layer 130 comprising W, a second conformal barrier layer 131 comprising Si02or AI2O3, and a second conformal dielectric layer 140 comprising Ti02or Fe203.

[0113] As described above, layer thicknesses and materials affect the optical properties of the OSC multilayer structure, and the ALD disclosed herein provides ultra-thin layer deposition with nanometer-scale precision and extremely low cross-layer material penetration. The optical properties of the OSC multilayer structure will now be described.

[0114] The optical properties of the OSC multilayer structure are affected by the optical layers of the multilayer structure. Referring again toFigure 1 The multilayer structure 100 according to the embodiments disclosed and described herein comprises a substrate 110, a conformal dielectric layer 120 encapsulating the substrate 110, and a conformal absorbing layer 130 encapsulating the conformal dielectric layer 120. The multilayer structure 100 disclosed and described herein consists of three“optical layers” (substrate 110, dielectric layer 120, and absorbing layer 130). These three optical layers influence the optical properties of the multilayer structure 100. The term“optical layer” as used herein does not include barrier layers, protective layers, and outer protective layers, which do not influence the optical properties of the multilayer structure.

[0115] Generally, the optical properties (e.g. absorption and reflection wavelengths, chroma, and hue) of a multilayer structure depend on the configuration of the multilayer structure. The influence of the layer configuration on the chroma and hue of a multilayer structure will now be described. For example, Figures 3A-3C and Figure 4 Simulated effects of different multilayer structures to obtain a desired level of hue in the red region of the visible spectrum are depicted, as plotted or illustrated on the Lab color space. As Figures 3A-3C shown, the simulation considers three simple multilayer structures, wherein each multilayer structure independently has two optical layers, including a reflective core particle and a first layer, which is either a dielectric layer or an absorbing layer encapsulating the reflective core particle. Figure 3A a ZnS dielectric layer 120a extending over the reflective core layer 110, Figure 3B a Si semiconductor absorbing layer 120b extending over the reflective core layer 110, and Figure 3C a Fe203absorbing layer 120c extending over the reflective core layer 110. For Figure 2 A to Figure 2 C, the reflectivity of each multilayer structure is simulated as a function of different thicknesses of the dielectric layer 120a, the semiconductor absorbing layer 120b, and the absorbing layer 120c.

[0116] Referring to Figure 4 , the simulation results are plotted on the Lab color space, also known as a color chart.Each data point shown in Figure 4 provides the chroma and hue of a ZnS dielectric layer for the first multilayer structure, a Si semiconductor absorbing layer for the second multilayer structure, or a Fe203dielectric absorbing layer for the third multilayer structure at a specific thickness.

[0117] The chroma value provides a measure of the“lightness” of a color, and the hue value provides a measure of the color (e.g. red, green, blue, yellow, etc.) displayed by an object. Hue can also refer to the angle of a given data point relative to the positive axis on the Lab color space (also known as a color chart). On the Lab color space, chroma can be defined as, and hue can be defined as .like Figure 4 As shown, with Figure 3B and Figure 3C Compared to the multi-layered structure shown in the figure, Figure 3A The multilayer structure shown provides low chromaticity. Therefore, Figures 3A-3C and Figure 4 This indicates that when a high chromaticity color is desired, an absorption layer (e.g., an absorbing layer) is preferable to a dielectric layer as the first layer extending on the reflective core layer. It should be understood that... Figure 4 The Lab color space analysis shown is for illustrative purposes, and multilayer structures according to the embodiments disclosed and described herein may have different Lab color space values. For example, in an embodiment, a multilayer structure may represent blue, green, yellow, or other colors in the Lab color space.

[0118] The effect of layer thickness on the chromaticity and hue of three multilayer structures will now be described. (Refer to...) Figures 5A-5C This describes chroma and hue as functions of layer thickness. Specifically, Figure 5A The chroma and hue are depicted graphically as Figure 3A The figure shows a function of the thickness of the ZnS dielectric layer extending on the Al reflective core layer. Figure 5B Describing chroma and hue as Figure 3B The figure shows the thickness of the Si semiconductor absorbing layer extending on the Al reflective core layer as a function of the thickness of the core layer. Figure 5C Describing chroma and hue as Figure 5C The figure shows the thickness of the Fe2O3 absorbing layer extending on the Al reflective core layer as a function of the thickness of the layer. Figures 5A-5C The dashed lines in the diagram correspond to the desired hue values ​​from 10° to 30° in the Lab color space. Figures 5A-5C A multilayer structure with an absorption layer extending on a reflective core layer is shown, achieving high chromaticity values ​​within a hue range of 10° to 30°. Similarly, it should be understood that... Figures 5A-5C The hues and chromaticities shown are for illustrative purposes, and the multi-layered structures of the embodiments disclosed and described herein may have different hue and chromaticity values.

[0119] The effect of layer thickness on the absorption and reflection wavelengths will now be described. Assume... Figure 1 The multilayer structure shown includes three optical layers: a conformal absorption layer 130 encapsulates a conformal dielectric layer 120, the conformal dielectric layer 120 encapsulates a reflective core particle 110, and the position of the conformal absorption layer is selected to increase absorption of the target light wavelength. For example, if the multilayer structure is configured to absorb electromagnetic radiation with wavelengths less than or equal to 550 nm, but reflect electromagnetic radiation with wavelengths of approximately 650 nm, such as visible light outside the 10° to 30° hue range, then the absorption layer is placed within an electric field ( less than the thickness at a wavelength of 650 nm. Mathematically, this can be expressed as:

[0120]

[0121] and preferably:

[0122]

[0123] Figure 6 And the following discussion provides a method for calculating the thickness of a zero or near zero electric field point at a given wavelength of light according to embodiments. For the purposes of this specification, the term "near zero" is defined as . Figure 6 A multilayer structure is shown having a dielectric layer 4 on a substrate layer 2 having a refractive index of "n s ". The substrate layer 2 can be a core layer, a core particle, a reflective core layer, or a reflective core particle of the multilayer structure. Incident light impinges on the outer surface 5 of the dielectric layer 4 at an angle Θ relative to a line 6 normal to the outer surface 5 and reflects from the outer surface 5 at the same angle Θ. The incident light impinges on the surface 3 of the substrate layer 2 at an angle transmits through the outer surface 5 and into the dielectric layer 4 and impinges on the surface 3 of the substrate layer 2 at an angle For a single dielectric layer, and when z = d, the energy / field (E) can be expressed as E(z). According to Maxwell's equations, for s polarization, the electric field can be expressed as:

[0124]

[0125] and for p polarization, the electric field can be expressed as

[0126]

[0127] where , λ is the desired reflection wavelength, where "s" corresponds to the substrate, and is the dielectric constant of the layer as a function of z. Thus:

[0128] For s polarization,

[0129] ,

[0130] and for p polarization,

[0131] .

[0132] It is understood that the variation of the electric field along the Z direction of the dielectric layer 4 can be estimated by calculating the unknown parameters u(z) and v(z), which can be shown as:

[0133]

[0134] where 'i' is the square root of -1, and φ is the phase thickness of the dielectric layer 4. Using the boundary conditions , and the following relationships:

[0135] For s polarization,

[0136] For p polarization,

[0137] For s polarization,

[0138] For p polarization,

[0139]

[0140] u(z) and v(z) can be expressed as:

[0141]

[0142] and

[0143]

[0144] Thus:

[0145] For s polarization,

[0146]

[0147] where and:

[0148] For p polarization,

[0149]

[0150] where:

[0151]

[0152] and

[0153]

[0154] Thus, for the simple case where or normal incidence, and ​

[0155]

[0156]

[0157] Thus allowing the thickness "d" (i.e., the location or point within the dielectric layer where the electric field is zero) to be solved. It should be understood that the thickness "d" can be such a thickness of the first conformal dielectric layer 120, the first conformal barrier layer 121, and the first conformal protective layer 111 that encapsulates the core particle 110 that provides a zero or near zero electric field at the interface between the first conformal dielectric layer 120 and the conformal absorbing layer 130. It should also be understood that the thickness "d" can also be such a thickness of the second conformal dielectric layer 140 that encapsulates the second conformal protective layer 131 that provides a zero or near zero electric field at the interface between the second conformal dielectric layer 140 and the conformal absorbing layer 130, depending on the thickness "d" where the electric field is zero or near zero.

[0158] According to one or more embodiments, the conformal dielectric layer 120 can have a thickness greater than or equal to 5 nm and less than or equal to 500 nm, such as greater than or equal to 50 nm and less than or equal to 500 nm, greater than or equal to 100 nm and less than or equal to 500 nm, greater than or equal to 200 nm and less than or equal to 500 nm, greater than or equal to 300 nm and less than or equal to 500 nm, greater than or equal to 400 nm and less than or equal to 500 nm, greater than or equal to 450 nm and less than or equal to 500 nm, greater than or equal to 475 nm and less than or equal to 500 nm, greater than or equal to 5 nm and less than or equal to 475 nm, greater than or equal to 50 nm and less than or equal to 475 nm, greater than or equal to 100 nm and less than or equal to 475 nm, greater than or equal to 200 nm and less than or equal to 475 nm, greater than or equal to 300 nm and less than or equal to 475 nm, greater than or equal to 400 nm and less than or equal to 475 nm, greater than or equal to 450 nm and less than or equal to 475 nm, greater than or equal to 5 nm and less than or equal to 450 nm, greater than or equal to 50 nm and less than or equal to 450 nm, greater than or equal to 100 nm and less than or equal to 450 nm, greater than or equal to 200 nm and less than or equal to 450 nm, greater than or equal to 300 nm and less than or equal to 450 nm, greater than or equal to 400 nm and less than or equal to 450 nm, greater than or equal to 425 nm and less than or equal to 450 nm, greater than or equal to 5 nm and less than or equal to 400 nm, greater than or equal to 50 nm and less than or equal to 400 nm, greater than or equal to 100 nm and less than or equal to 400 nm, greater than or equal to 200 nm and less than or equal to 400 nm, greater than or equal to 300 nm and less than or equal to 400 nm, greater than or equal to 350 nm and less than or equal to 400 nm, greater than or equal to 5 nm and less than or equal to 350 nm, greater than or equal to 50 nm and less than or equal to 350 nm, greater than or equal to 100 nm and less than or equal to 350 nm, greater than or equal to 200 nm and less than or equal to 350 nm, greater than or equal to 300 nm and less than or equal to 350 nm, greater than or equal to 325 nm and less than or equal to 350 nm, greater than or equal to 5 nm and less than or equal to 300 nm, greater than or equal to 50 nm and less than or equal to 300 nm, greater than or equal to 100 nm and less than or equal to 300 nm, greater than or equal to 200 nm and less than or equal to 300 nm, greater than or equal to 250 nm and less than or equal to 300 nm, greater than or equal to 5 nm and less than or equal to 250 nm, greater than or equal to 50 nm and less than or equal to 250 nm, greater than or equal to 100 nm and less than or equal to 250 nm, greater than or equal to 200 nm and less than or equal to 250 nm, greater than or equal to 5 nm and less than or equal to 200 nm, greater than or equal to 50 nm and less than or equal to 200 nm, greater than or equal to 100 nm and less than or equal to 200 nm, greater than or equal to 150 nm and less than or equal to 200 nm, greater than or equal to 5 nm and less than or equal to 150 nm, greater than or equal to 50 nm and less than or equal to 150 nm, greater than or equal to 100 nm and less than or equal to 150 nm, greater than or equal to 5 nm and less than or equal to 100 nm, greater than or equal to 50 nm and less than or equal to 100 nm, greater than or equal to 5 nm and less than or equal to 50 nm, greater than or equal to 5 nm and less than or equal to 25 nm, or greater than or equal to 5 nm and less than or equal to 10 nm.nm and less than or equal to 250 nm, greater than or equal to 200 nm and less than or equal to 250 nm, greater than or equal to 5 nm and less than or equal to 200 nm, greater than or equal to 50 nm and less than or equal to 200 nm, greater than or equal to 100 nm and less than or equal to 200 nm, greater than or equal to 150 nm and less than or equal to 200 nm, greater than or equal to 5 nm and less than or equal to 100 nm, greater than or equal to 50 nm and less than or equal to 100 nm, greater than or equal to 75 nm and less than or equal to 100 nm, greater than or equal to 5 nm and less than or equal to 50 nm, greater than or equal to 15 nm and less than or equal to 50 nm, greater than or equal to 30 nm and less than or equal to 50 nm, greater than or equal to 5 nm and less than or equal to 30 nm, greater than or equal to 15 nm and less than or equal to 30 nm, or greater than or equal to 5 nm and less than or equal to 15 nm.

[0159] In embodiments, the conformal absorbing layer 130 can have a thickness greater than or equal to 2 nm and less than or equal to 50 nm, such as greater than or equal to 2 nm and less than or equal to 45 nm, greater than or equal to 2 nm and less than or equal to 40 nm, greater than or equal to 2 nm and less than or equal to 35 nm, greater than or equal to 2 nm and less than or equal to 30 nm, greater than or equal to 2 nm and less than or equal to 25 nm, greater than or equal to 2 nm and less than or equal to 20 nm, greater than or equal to 5 nm and less than or equal to 20 nm, greater than or equal to 8 nm and less than or equal to 20 nm, greater than or equal to 10 nm and less than or equal to 20 nm, greater than or equal to 12 nm and less than or equal to 20 nm, greater than or equal to 15 nm and less than or equal to 20 nm, greater than or equal to 18 nm and less than or equal to 20 nm, greater than or equal to 2 nm and less than or equal to 18 nm, greater than or equal to 5 nm and less than or equal to 18 nm, greater than or equal to 8 nm and less than or equal to 18 nm, greater than or equal to 10 nm and less than or equal to 18 nm, greater than or equal to 12 nm and less than or equal to 18 nm, greater than or equal to 15 nm and less than or equal to 18 nm, greater than or equal to 2 nm and less than or equal to 15 nm, greater than or equal to 5 nm and less than or equal to 15 nm, greater than or equal to 8 nm and less than or equal to 15 nm, greater than or equal to 10 nm and less than or equal to 15 nm, greater than or equal to 12 nm and less than or equal to 15 nm, greater than or equal to 2 nm and less than or equal to 12 nm, greater than or equal to 5 nm and less than or equal to 12 nm, greater than or equal to 8 nm and less than or equal to 12 nm, greater than or equal to 10 nm and less than or equal to 12 nm, greater than or equal to 2 nm and less than or equal to 10 nm, greater than or equal to 5 nm and less than or equal to 10 nm, greater than or equal to 8 nm and less than or equal to 10 nm, greater than or equal to 2 nm and less than or equal to 8 nm, greater than or equal to 5 nm and less than or equal to 8 nm, or greater than or equal to 2 nm and less than or equal to 5 nm.

[0160] In embodiments, the second conformal dielectric layer 140 can have a thickness greater than or equal to 5 nm and less than or equal to 500 nm, such as greater than or equal to 50 nm and less than or equal to 500 nm, greater than or equal to 100 nm and less than or equal to 500 nm, greater than or equal to 200 nm and less than or equal to 500 nm, greater than or equal to 300 nm and less than or equal to 500 nm, greater than or equal to 400 nm and less than or equal to 500 nm, greater than or equal to 450 nm and less than or equal to 500 nm, greater than or equal to 475 nm and less than or equal to 500 nm, greater than or equal to 5 nm and less than or equal to 475 nm, greater than or equal to 50 nm and less than or equal to 475 nm, greater than or equal to 100 nm and less than or equal to 475 nm, greater than or equal to 200 nm and less than or equal to 475 nm, greater than or equal to 300 nm and less than or equal to 475 nm, greater than or equal to 400 nm and less than or equal to 475 nm, greater than or equal to 450 nm and less than or equal to 475 nm, greater than or equal to 5 nm and less than or equal to 450 nm, greater than or equal to 50 nm and less than or equal to 450 nm, greater than or equal to 100 nm and less than or equal to 450 nm, greater than or equal to 200 nm and less than or equal to 450 nm, greater than or equal to 300 nm and less than or equal to 450 nm, greater than or equal to 400 nm and less than or equal to 450 nm, greater than or equal to 425 nm and less than or equal to 450 nm, greater than or equal to 5 nm and less than or equal to 400 nm, greater than or equal to 50 nm and less than or equal to 400 nm, greater than or equal to 100 nm and less than or equal to 400 nm, greater than or equal to 200 nm and less than or equal to 400 nm, greater than or equal to 300 nm and less than or equal to 400 nm, greater than or equal to 350 nm and less than or equal to 400 nm, greater than or equal to 5 nm and less than or equal to 350 nm, greater than or equal to 50 nm and less than or equal to 350 nm, greater than or equal to 100 nm and less than or equal to 350 nm, greater than or equal to 200 nm and less than or equal to 350 nm, greater than or equal to 300 nm and less than or equal to 350 nm, greater than or equal to 325 nm and less than or equal to 350 nm, greater than or equal to 5 nm and less than or equal to 300 nm, greater than or equal to 50 nm and less than or equal to 300 nm, greater than or equal to 100 nm and less than or equal to 300 nm, greater than or equal to 200 nm and less than or equal to 300 nm, greater than or equal to 250 nm and less than or equal to 300 nm, greater than or equal to 5 nm and less than or equal to 250 nm, greater than or equal to 50 nm and less than or equal to 250 nm, greater than or equal to 100 nm and less than or equal to 250 nm, greater than or equal to 200 nm and less than or equal to 250 nm, greater than or equal to 5 nm and less than or equal to 200 nm, greater than or equal to 50 nm and less than or equal to 200 nm, greater than or equal to 100 nm and less than or equal to 200 nm, greater than or equal to 150 nm and less than or equal to 200 nm, greater than or equal to 5 nm and less than or equal to 150 nm, greater than or equal to 50 nm and less than or equal to 150 nm, greater than or equal to 100 nm and less than or equal to 150 nm, greater than or equal to 5 nm and less than or equal to 100 nm, greater than or equal to 50 nm and less than or equal to 100 nm, greater than or equal to 5 nm and less than or equal to 50 nm, greater than or equal to 5 nm and less than or equal to 25 nm, or greater than or equal to 5 nm and less than or equal to 10 nm.nm, greater than or equal to 200 nm and less than or equal to 250 nm, greater than or equal to 5 nm and less than or equal to 200 nm, greater than or equal to 50 nm and less than or equal to 200 nm, greater than or equal to 100 nm and less than or equal to 200 nm, greater than or equal to 150 nm and less than or equal to 200 nm, greater than or equal to 5 nm and less than or equal to 100 nm, greater than or equal to 50 nm and less than or equal to 100 nm, greater than or equal to 75 nm and less than or equal to 100 nm, greater than or equal to 5 nm and less than or equal to 50 nm, greater than or equal to 15 nm and less than or equal to 50 nm, greater than or equal to 30 nm and less than or equal to 50 nm, greater than or equal to 5 nm and less than or equal to 30 nm, greater than or equal to 15 nm and less than or equal to 30 nm, or greater than or equal to 5 nm and less than or equal to 15 nm.

[0161] In embodiments, the thickness of the conformal barrier layer 121 can be less than or equal to 50 nm, for example, less than or equal to 48 nm, less than or equal to 45 nm, less than or equal to 42 nm, less than or equal to 40 nm, less than or equal to 38 nm, less than or equal to 35 nm, less than or equal to 32 nm, less than or equal to 30 nm, less than or equal to 28 nm, less than or equal to 25 nm, less than or equal to 22 nm, less than or equal to 20 nm, less than or equal to 18 nm, less than or equal to 15 nm, less than or equal to 12 nm, less than or equal to 10 nm, less than or equal to 8 nm, less than or equal to 5 nm, or less than or equal to 2 nm.

[0162] In embodiments, the thickness of the second conformal barrier layer 131 can be less than or equal to 50 nm, for example, less than or equal to 48 nm, less than or equal to 45 nm, less than or equal to 42 nm, less than or equal to 40 nm, less than or equal to 38 nm, less than or equal to 35 nm, less than or equal to 32 nm, less than or equal to 30 nm, less than or equal to 28 nm, less than or equal to 25 nm, less than or equal to 22 nm, less than or equal to 20 nm, less than or equal to 18 nm, less than or equal to 15 nm, less than or equal to 12 nm, less than or equal to 10 nm, less than or equal to 8 nm, less than or equal to 5 nm, or less than or equal to 2 nm.

[0163] According to one or more embodiments, the outer protective layer 141 has a thickness less than or equal to 30 nm, such as less than or equal to 25 nm, less than or equal to 20 nm, less than or equal to 15 nm, or less than or equal to 20 nm. In embodiments, the outer protective layer 141 has a thickness greater than or equal to 5 nm and less than or equal to 15 nm, such as greater than or equal to 6 nm and less than or equal to 14 nm, greater than or equal to 7 nm and less than or equal to 13 nm, or greater than or equal to 8 nm and less than or equal to 12 nm.

[0164] According to one or more embodiments, the protective layer 111 has a thickness greater than or equal to 3 nm and less than or equal to 15 nm, such as greater than or equal to 5 nm and less than or equal to 13 nm, greater than or equal to 7 nm and less than or equal to 11 nm, or greater than or equal to 8 nm and less than or equal to 10 nm.

[0165] As disclosed herein, utilizing ALD processes allows for the deposition of multilayers with optical precision and vast material property differences (e.g., dielectric materials versus metallic materials as described above) on a large scale. Moreover, ALD processes allow for the production of multilayer structures with high density, low porosity, and full layer coverage, all with nanoscale precision.

[0166] The specific surface area (SSA) of the material was obtained by fitting 13 points collected from P / P0~ 0.06 to 0.3 to the Brunauer-Emmett-Teller (BET) equation using nitrogen physisorption isotherms at 76 K. Additional adsorption points were collected at different P / P0up to P / P0~ 0.95, followed by desorption back to P / P0~ 0.06. The total pore volume was determined from the volume of nitrogen adsorbed at P / P0~ 0.95, and the average pore diameter was calculated using the Barrett Joyner Halenda (BJH) method.

[0167] In one or more embodiments, each of the conformal dielectric layer 120, the conformal absorbing layer 130, and the second conformal dielectric layer 140 independently has a pore volume that can be less than or equal to 0.030 cm 3 / g, such as less than or equal to 0.025 cm 3 / g, such as less than or equal to 0.020 cm 3 / g, such as less than or equal to 0.015 cm 3 / g, such as less than or equal to 0.010 cm 3 / g, such as less than or equal to 0.009 cm 3 / g, such as less than or equal to 0.008 cm 3 / g, less than or equal to 0.007 cm 3 / g, less than or equal to 0.006 cm 3 / g, less than or equal to 0.005 cm 3 / g pore volume, less than or equal to 0.004 cm 3 / g, less than or equal to 0.003 cm 3 / g, less than or equal to 0.002 cm 3 / g, less than or equal to 0.001 cm 3 / g. It will be appreciated that in embodiments one or more of the conformal dielectric layer 120, the conformal absorbing layer 130, and the second conformal dielectric layer 140 can have the same pore volume, while in other embodiments one or more of the conformal dielectric layer 120, the conformal absorbing layer 130, and the second conformal dielectric layer 140 can have different pore volumes.

[0168] In one or more embodiments, the surface area of each of the conformal dielectric layer 120, the conformal absorbing layer 130, and the second conformal dielectric layer 140 is independently less than or equal to 100 square meters per gram (m 2 / g), for example less than or equal to 90 m 2 / g, less than or equal to 85 m 2 / g, less than or equal to 80 m 2 / g, less than or equal to 75 m 2 / g, less than or equal to 70 m 2 / g, less than or equal to 65 m 2 / g, less than or equal to 60 m 2 / g, less than or equal to 55 m 2 / g, less than or equal to 50 m 2 / g, less than or equal to 45 m 2 / g, less than or equal to 40 m 2 / g, less than or equal to 35 m 2 / g, less than or equal to 30 m 2 / g, less than or equal to 25 m 2 / g, less than or equal to 20 m 2 / g, less than or equal to 15 m 2 / g, less than or equal to 10 m 2 / g, for example less than or equal to 9 m 2 / g, less than or equal to 8 m 2 / g, less than or equal to 7 m 2 / g, less than or equal to 6 m 2 / g, less than or equal to 5 m 2 / g, less than or equal to 4 m2 / g, less than or equal to 3 m 2 / g, less than or equal to 2 m 2 / g, or less than or equal to 1 m 2 / g. Thus, in embodiments, each layer can independently have a surface area that can be greater than or equal to 2 m 2 / g and less than or equal to 10 m 2 / g, greater than or equal to 3 m 2 / g and less than or equal to 10 m 2 / g, greater than or equal to 3 m 2 / g and less than or equal to 8 m 2 / g, greater than or equal to 5 m 2 / g and less than or equal to 8 m 2 / g, greater than or equal to 1 m 2 / g and less than or equal to 3 m 2 / g, greater than or equal to 3 m 2 / g and less than or equal to 5 m 2 / g, greater than or equal to 2 m 2 / g and less than or equal to 3 m 2 / g, greater than or equal to 1 m 2 / g and less than or equal to 2 m 2 / g, or greater than or equal to 0.5 m 2 / g and less than or equal to 1 m 2 / g. It should be understood that in embodiments one or more of the conformal dielectric layer 120, the conformal absorbing layer 130, and the second conformal dielectric layer 140 can have the same surface area, while in other embodiments one or more of the first conformal dielectric layer 120, the conformal absorbing layer 130, and the second conformal dielectric layer 140 can have different surface areas.

[0169] In embodiments, the multilayer structure can have a D 50 diameter measured by the BET equation, which can be calculated from the amount of adsorbed gas that forms a monolayer on the surface at the temperature of measurement. The amount of molecules in this monolayer multiplied by the space required for one molecule yields the BET D 50which can be greater than or equal to 1 pm to less than or equal to 500 pm, for example, greater than or equal to 5 pm to less than or equal to 500 pm, greater than or equal to 10 pm to less than or equal to 500 pm, greater than or equal to 25 pm to less than or equal to 500 pm, greater than or equal to 100 pm to less than or equal to 500 pm, greater than or equal to 200 pm to less than or equal to 500 pm, greater than or equal to 250 pm to less than or equal to 500 pm, greater than or equal to 300 pm to less than or equal to 500 pm, greater than or equal to 350 pm to less than or equal to 500 pm, greater than or equal to 400 pm to less than or equal to 500 pm, greater than or equal to 450 pm to less than or equal to 500 pm, greater than or equal to 10 pm to less than or equal to 450 pm, greater than or equal to 25 pm to less than or equal to 450 pm, greater than or equal to 100 pm to less than or equal to 450 pm, greater than or equal to 200 pm to less than or equal to 450 pm, greater than or equal to 250 pm to less than or equal to 450 pm, greater than or equal to 300 pm to less than or equal to 450 pm, greater than or equal to 350 pm to less than or equal to 450 pm, greater than or equal to 400 pm to less than or equal to 450 pm, greater than or equal to 10 pm to less than or equal to 400 pm, greater than or equal to 25 pm to less than or equal to 400 pm, greater than or equal to 100 pm to less than or equal to 400 pm, greater than or equal to 200 pm to less than or equal to 400 pm, greater than or equal to 250 pm to less than or equal to 400 pm, greater than or equal to 300 pm to less than or equal to 400 pm, greater than or equal to 350 pm to less than or equal to 400 pm, greater than or equal to 10 pm to less than or equal to 350 pm, greater than or equal to 25 pm to less than or equal to 350 pm, greater than or equal to 50 pm to less than or equal to 350 pm, greater than or equal to 100 pm to less than or equal to 350 pm, greater than or equal to 200 pm to less than or equal to 350 pm, greater than or equal to 250 pm to less than or equal to 350 pm, greater than or equal to 300 pm to less than or equal to 350 pm, greater than or equal to 50 pm to less than or equal to 300 pm, greater than or equal to 100 pm to less than or equal to 300 pm, greater than or equal to 200 pm to less than or equal to 300 pm, greater than or equal to 250 pm to less than or equal to 300 pm, greater than or equal to 10 pm to less than or equal to 250 pm, greater than or equal to 25 pm to less than or equal to 250 pm, greater than or equal to 100 pm to less than or equal to 250 pm, greater than or equal to 200 pm to less than or equal to 250 pm, greater than or equal to 25 pm to less than or equal to 200 pm, greater than or equal to 50 pm to less than or equal to 200 pm, greater than or equal to 100 pm to less than or equal to 200 pm, greater than or equal to 150 pm to less than or equal to 200 pm, greater than or equal to 50 pm to less than or equal to 150 pm, greater than or equal to 100 pm to less than or equal to 150 pm, greater than or equal to 10 pm to less than or equal to 150 pm, greater than or equal to 25 pm to less than or equal to 150 pm, greater than or equal to 50 pm to less than or equal to 150 pm, greater than or equal to 10 pm to less than or equal to 100 pm, greater than or equal to 25 pm to less than or equal to 100 pm, greater than or equal to 50 pm to less than or equal to 100 pm, greater than or equal to 10 pm to less than or equal to 50 pm, greater than or equal to 25 pm to less than or equal to 50 pm, or greater than or equal to 10 pm to less than or equal to 25 pm.greater than or equal to 1 μm to less than or equal to 10 μm, greater than or equal to 5 μm to less than or equal to 10 μm, or greater than or equal to 1 μm to less than or equal to 5 μm.

[0170] Based on a large number of thin sections, the aspect ratio of the multilayer structures according to the embodiments disclosed and described herein can be greater than or equal to 1 and less than or equal to 100, for example, greater than or equal to 5 and less than or equal to 100, greater than or equal to 10 and less than or equal to 100, greater than or equal to 20 and less than or equal to 100, greater than or equal to 30 and less than or equal to 100, greater than or equal to 40 and less than or equal to 100, greater than or equal to 50 and less than or equal to 100, greater than or equal to 60 and less than or equal to 100, greater than or equal to 70 and less than or equal to 100, greater than or equal to 80 and less than or equal to 100, greater than or equal to 90 and less than or equal to 100, greater than or equal to 1 and less than or equal to 90, greater than or equal to 5 and less than or equal to 90, greater than or equal to 10 and less than or equal to 90, greater than or equal to 20 and less than or equal to 90, greater than or equal to 30 and less than or equal to 90, greater than or equal to 40 and less than or equal to 90, greater than or equal to 50 and less than or equal to 90, greater than or equal to 60 and less than or equal to 90, greater than or equal to 70 and less than or equal to 90, greater than or equal to 80 and less than or equal to 90, greater than or equal to 1 and less than or equal to 80, greater than or equal to 5 and less than or equal to 80, greater than or equal to 10 and less than or equal to 80, greater than or equal to 20 and less than or equal to 80, greater than or equal to 30 and less than or equal to 80, greater than or equal to 40 and less than or equal to 80, greater than or equal to 50 and less than or equal to 80, greater than or equal to 60 and less than or equal to 80, greater than or equal to 70 and less than or equal to 80, greater than or equal to 1 and less than or equal to 70, greater than or equal to 5 and less than or equal to 70, greater than or equal to 10 and less than or equal to 70, greater than or equal to 20 and less than or equal to 70, greater than or equal to 30 and less than or equal to 70, greater than or equal to 40 and less than or equal to 70, greater than or equal to 50 and less than or equal to 70, greater than or equal to 60 and less than or equal to 70, greater than or equal to 1 and less than or equal to 60, greater than or equal to 5 and less than or equal to 60, greater than or equal to 10 and less than or equal to 60, greater than or equal to 20 and less than or equal to 60, greater than or equal to 30 and less than or equal to 60, greater than or equal to 40 and less than or equal to 60, greater than or equal to 50 and less than or equal to 60, greater than or equal to 1 and less than or equal to 50, greater than or equal to 5 and less than or equal to 50, greater than or equal to 10 and less than or equal to 50, greater than or equal to 20 and less than or equal to 50, greater than or equal to 30 and less than or equal to 50, greater than or equal to 40 and less than or equal to 50, greater than or equal to 1 and less than or equal to 40, greater than or equal to 5 and less than or equal to 40, greater than or equal to 10 and less than or equal to 40, greater than or equal to 20 and less than or equal to 40, greater than or equal to 30 and less than or equal to 40, greater than or equal to 1 and less than or equal to 30, greater than or equal to 5 and less than or equal to 30,greater than or equal to 10 and less than or equal to 30, greater than or equal to 20 and less than or equal to 30, greater than or equal to 1 and less than or equal to 20, greater than or equal to 5 and less than or equal to 20, greater than or equal to 10 and less than or equal to 20, greater than or equal to 1 and less than or equal to 10, greater than or equal to 5 and less than or equal to 10, or greater than or equal to 1 and less than or equal to 5.

[0171] The multilayer structures in the embodiments disclosed herein can be used as pigments (e.g., paint pigments for paint that is brushed onto an object), or as a continuous film applied to an object. When used as pigments, at least one of a paint binder and a filler can be used and mixed with the pigments to provide a paint that exhibits high chromatic structural color. In addition, other additives can be added to the multilayer structure to aid in the compatibility of the multilayer structure in a paint system. Exemplary compatibility enhancing additives include silane surface treatment agents that coat the exterior of the multilayer structure and improve the compatibility of the multilayer structure in a paint system. Such paint systems or films can be used in any article, including automotive vehicles.

[0172] Embodiments

[0173] The embodiments will be further clarified by the following examples.

[0174] As noted above, high volume ALD production can result in the overlap of adjacent dielectric and absorbing layers, which can result in the deterioration of the optical properties of the multilayer structure. This overlap is believed to occur due to the high porosity of the dielectric layer (e.g., Ti02layer), which allows for overlap with the absorbing layer (e.g., W layer) applied by ALD, as the metal can soak into the pores of the dielectric layer. With the barrier or protection layer, all layers are well separated, and thus their optical properties are well predicted by simulation.

[0175] Example 1

[0176] A multilayer structure was formed using an ALD process. The multilayer structure included an aluminum reflective core layer, a conformal Si02first protection layer encapsulating the reflective core layer, a conformal Ti02dielectric layer encapsulating the conformal Si02protection layer, a conformal AI2O3barrier layer encapsulating the conformal Ti02dielectric layer, and a conformal W absorbing layer encapsulating the conformal AI2O3barrier layer.

[0177] Figure 7A A TEM image of the formed multilayer structure is shown in FIG. 1. As shown in FIG. 1, the layers are clear, separated, and have smooth surfaces. Figure 7A A further magnified TEM image of the formed multilayer structure is shown in FIG. 2, and further shows clear, separated, and smooth layers. Figure 7B A TEM image of the formed multilayer structure is shown in FIG. 1. As shown in FIG. 1, the layers are clear, separated, and have smooth surfaces. Figure 7C A TEM image of the formed multilayer structure is shown in FIG. 1. As shown in FIG. 1, the layers are clear, separated, and have smooth surfaces. Figure 7CThe Al reflective core layer 710 is clearly visible and has a smooth surface, and it also shows a clear Al2O3 barrier layer 731, both of which have smooth surfaces. Figure 7D A TEM image highlighting the element oxygen. Figure 7D It shows a clear SiO2 protective layer 711, a clear TiO2 dielectric layer 720 and a clear Al2O3 barrier layer 731, all of which have smooth surfaces and no significant overlap between the oxygen-containing layers. Figure 7E A TEM image highlighting the element tungsten. For example... Figure 7E As shown, the W absorption layer 730 has a clear and smooth surface. Figure 7E It was also shown that no tungsten penetrated into the TiO2 dielectric layer 720. Figure 7F A TEM image highlighting the element titanium. Figure 7F A clear TiO2 dielectric layer 720 with a smooth surface is displayed, and no TiO2 penetrates into the Al reflective core layer 710 or the W absorber layer 730.

[0178] Comparative Example 1

[0179] A multilayer structure is formed using the ALD process. The multilayer structure includes an aluminum reflective core layer, a conformal SiO2 protective layer encapsulating the reflective core layer, a conformal TiO2 dielectric layer encapsulating the conformal SiO2 protective layer, and a conformal W absorber layer encapsulating the conformal TiO2 dielectric layer. There is no barrier layer between the TiO2 dielectric layer and the W absorber layer.

[0180] Figure 8 illustrates the penetration of tungsten from the metal layer into the adjacent porous TiO2 dielectric layer. Specifically, Figure 8A TEM images of the multilayer structure before the deposition of the W absorption layer, and Figure 8B for Figure 8A Enlarged TEM images. In Figure 8B In this multilayer structure, there is an aluminum reflective core layer, a conformal SiO2 protective layer encapsulating the reflective core layer, and a conformal TiO2 dielectric layer encapsulating the conformal SiO2 protective layer. For example... Figure 8B As shown, the conformal TiO2 dielectric layer appears to be porous. Figure 8C This is a TEM image of the multilayer structure after the deposition of the W absorption layer. (Example:) Figure 8C As shown, tungsten permeates from the W absorber layer into the TiO2 dielectric layer. Figure 8D This is a further magnified TEM image of the multilayer structure, which further shows W penetrating into the TiO2 dielectric layer. Figure 8E A TEM image highlighting the element aluminum. Figure 8E As shown, the Al reflective core layer 710 is very clear and has a smooth surface partially provided by the SiO2 protective layer. Figure 8F A TEM image highlighting the element oxygen.Figure 8F It is shown that the oxygen concentration is more dense at the bottom of the TiO2dielectric layer (i.e., closer to the Al reflective core layer), where less tungsten is able to penetrate into the TiO2. Figure 8G is a TEM image where the element tungsten is highlighted. As Figure 8G shown, there is no barrier layer, and W penetrates into the TiO2. Figure 8H is a TEM image of a multilayer structure without a barrier layer where the element carbon is highlighted; carbon is the main component of the resin used to support the pigments; Figure 8I is a TEM image where the element titanium is highlighted. Figure 8I It is shown that the higher Ti concentration is at the bottom of the TiO2dielectric layer (i.e., closer to the Al reflective core layer), where less tungsten is able to penetrate into the TiO2.

[0181] As shown in Example 1 and Comparative Example 1 above, by depositing an Al2O3barrier layer between the TiO2dielectric layer and the W absorbing layer, the multilayer structure has well separated dielectric and absorbing layers, which results in a multilayer structure with improved chromaticity compared to a multilayer structure where there is no barrier layer between the TiO2dielectric layer and the W absorbing layer.

[0182] Example 2

[0183] Two paint systems were formed using the multilayer structures described in Example 1 and Comparative Example 1. Figure 9 The chromaticity of the two paint systems was compared. In Figure 9 the left side, the paint system was formed using the multilayer structure described in Example 1. In Figure 9 the right side, the paint system was formed using the multilayer structure described in Comparative Example 1. Figure 9 It is shown that the paint system containing the multilayer structure described in Example 1 has a chromatically enhanced blue color, in contrast, the paint system containing the multilayer structure described in Comparative Example 1 has a shifted blue hue and reduced chromaticity.

[0184] Example 3

[0185] The effect of the thickness of the tungsten absorbing layer and the TiO2dielectric layer was investigated in this example. Figure 10A and Figure 10B Two sets of four multilayer structures are shown that include three optical layers deposited using an ALD process. The three optical layers include an Al reflective core layer, a TiO2dielectric layer, and a W absorbing layer.

[0186] Figure 10A A set of three layer structures is shown that include W absorbing layers with thicknesses of 5 nm, 7 nm, 9 nm, and 12 nm, and a TiO2dielectric layer with a fixed thickness of 50 nm. As Figure 10AAs shown, as the thickness of the W absorption layer increases, the reflectivity curve shifts slightly to lower wavelengths and becomes more reflective. Figure 10B A set of three-layer structures including a fixed thickness of 5 nm W absorption layer and Ti02dielectric layers with thicknesses of 42 nm, 45 nm, 48 nm, and 50 nm were shown. As shown in FIG. 4, as the thickness of the titanium dioxide layer increases, the reflectivity curve shifts slightly to lower wavelengths. Figure 10B As shown, as the thickness of the W absorption layer increases, the reflectivity curve shifts slightly to lower wavelengths and becomes more reflective.

[0187] Both sets of samples performed significantly better than seven-layer structures formed by vacuum deposition.

[0188] Example 4

[0189] This example compares the density, surface area, and pore volume of multilayer structures fabricated using the ALD process and wet chemistry. As shown in Table 1 below, the density of the multilayer structures fabricated by the ALD method and wet chemistry are the same, but the surface area of the multilayer structures using the ALD method is much smaller.

[0190] Table 1

[0191]

[0192] The density of the pigment is the ratio of the mass of the pigment sample to its volume, including the contribution of the inter-particle void volume. To measure this density, a glass cylinder with a specific volume is used, and a known mass of pigment is introduced into the cylinder. The volume is estimated by adding DI water to the cylinder until the water reaches the volume line of the cylinder. The volume of water is obtained by measuring the weight of the added DI water. The volume of the sample is obtained by subtracting the volume of water from the total volume of the cylinder. Replicate experiments are performed to determine the density. After degassing at 90 °C for 1 hour, and then at 150 °C for 3 hours, a complete adsorption / desorption isotherm is collected for the sample. The specific surface area (SSA) of the material is obtained by fitting 13 points collected from P / P0~ 0.06 to 0.3 to the Brunauer-Emmett-Teller (BET) equation using nitrogen physisorption at 76 K. Additional adsorption points are collected at different P / P0until P / P0~ 0.95, followed by desorption back to P / P0~ 0.06. The total pore volume is determined from the volume of nitrogen adsorbed at P / P0~ 0.95, and the average pore diameter is calculated using the Barrett Joyner Halenda (BJH) method.

[0193] It will be apparent to those skilled in the art that various modifications and variations can be made to the embodiments described herein without departing from the spirit or scope of the claimed subject matter. Thus, it is intended that the specification cover the modifications and variations of the various embodiments described herein came within the scope of the appended claims and their equivalents.

Claims

1. A method of forming a multilayer structure of a reflective omnidirectional structural color by atomic layer deposition (ALD), comprising: introducing at least one reflective core particle into a reaction chamber; depositing a conformal dielectric layer encapsulating the at least one reflective core particle in a dielectric layer ALD cycle; depositing a conformal barrier layer encapsulating the conformal dielectric layer in a barrier layer ALD cycle; and depositing a conformal absorber layer encapsulating the conformal barrier layer in an absorber layer ALD cycle.

2. The method of claim 1, wherein the at least one reflective core particle comprises a conformal protective layer encapsulating the at least one reflective core particle.

3. The method of claim 2, wherein the conformal protective layer is formed by ALD, CVD, or wet chemistry.

4. The method of claim 1, further comprising depositing a conformal outer protective layer encapsulating the conformal absorber layer in an outer protective layer ALD cycle.

5. The method of claim 1, further comprising depositing a second conformal barrier layer encapsulating the conformal absorber layer in a second barrier layer ALD cycle; and depositing a second conformal dielectric layer encapsulating the second conformal barrier layer in a second dielectric layer ALD cycle.

6. The method of claim 5, further comprising depositing a conformal outer protective layer encapsulating the second conformal dielectric layer in an outer protective layer ALD cycle.

7. The method of claim 1, wherein the dielectric layer ALD cycle comprises, in order: supplying a first precursor selected from halides, alkyls, alkoxides, alkylamides, and carbonyls of Ti, Zn, Zr, Hf, Fe, Al, Pb, Ga, In, Si, Mg, K, and combinations thereof into the reaction chamber; purging the reaction chamber with a purge gas selected from nitrogen, argon, and combinations thereof; supplying a second precursor selected from O2, O3, H2O, H2O2, As2O3, As2O5, H2S, S2, Br2, HF, NH4F, SF6, and combinations thereof into the reaction chamber; and purging the reaction chamber with a purge gas selected from nitrogen, argon, and combinations thereof.

8. The method of claim 1, wherein the barrier layer ALD cycle comprises, in order: supplying a first precursor selected from halides, alkyls, alkoxides, alkylamides, and carbonyls of Al, Si, Mg, K, Zn, and combinations thereof into the reaction chamber; purging the reaction chamber with a purge gas selected from nitrogen, argon, and combinations thereof; supplying a second precursor selected from O2, O3, H2O, H2O2, Br2, HF, NH4F, and combinations thereof into the reaction chamber; and purging the reaction chamber with a purge gas selected from nitrogen, argon, and combinations thereof.

9. The method of claim 1, wherein the absorber layer ALD cycle comprises, in order: supplying a first precursor selected from halides, alkyls, alkoxides, alkylamides, and carbonyls of W, Cr, Ge, Ni, Pd, Ti, Si, V, Co, Mo, Nb, and combinations thereof into the reaction chamber; purging the reaction chamber with a purge gas selected from nitrogen, argon, and combinations thereof; ​ supplying a first component selected from the group consisting of halides, alkyls, alkoxides, alkylamides, and carbonyls of Al, Si, Mg, K, Zn, and combinations thereof into the reaction chamber; purging the reaction chamber with a purge gas selected from the group consisting of nitrogen, argon, and combinations thereof.

10. The method of claim 4, wherein the outer protective layer ALD cycle comprises, in order: supplying a first component selected from the group consisting of halides, alkyls, alkoxides, alkylamides, and carbonyls of Al, Si, Mg, K, Zn, and combinations thereof into the reaction chamber; purging the reaction chamber with a purge gas selected from the group consisting of nitrogen, argon, and combinations thereof; supplying a second component selected from the group consisting of O2, O3, H2O, H2O2, Br2, HF, NH4F, and combinations thereof into the reaction chamber; purging the reaction chamber with a purge gas selected from the group consisting of nitrogen, argon, and combinations thereof; supplying trimethylaluminum and water into the reaction chamber; and purging the reaction chamber with a purge gas selected from the group consisting of nitrogen, argon, and combinations thereof.

11. The method of claim 5, wherein the second barrier layer ALD cycle comprises, in order: supplying a first component selected from the group consisting of halides, alkyls, alkoxides, alkylamides, and carbonyls of Al, Si, Mg, K, Zn, and combinations thereof into the reaction chamber; purging the reaction chamber with a purge gas selected from the group consisting of nitrogen, argon, and combinations thereof; supplying a second component selected from the group consisting of O2, O3, H2O, H2O2, Br2, HF, NH4F, and combinations thereof into the reaction chamber; and purging the reaction chamber with a purge gas selected from the group consisting of nitrogen, argon, and combinations thereof.

12. The method of claim 5, wherein the second dielectric layer ALD cycle comprises, in order: supplying a first component selected from the group consisting of halides, alkyls, alkoxides, alkylamides, and carbonyls of Ti, Zn, Zr, Hf, Fe, Al, Pb, Ga, In, Si, Mg, K, and combinations thereof into the reaction chamber; purging the reaction chamber with a purge gas selected from the group consisting of nitrogen, argon, and combinations thereof; supplying a second component selected from the group consisting of O2, O3, H2O, H2O2, As2O3, As2O5, H2S, S2, Br2, HF, NH4F, SF6, and combinations thereof into the reaction chamber; and purging the reaction chamber with a purge gas selected from the group consisting of nitrogen, argon, and combinations thereof.

13. The method of claim 1, wherein in each of the dielectric layer ALD cycle, the barrier layer ALD cycle, and the absorber layer ALD cycle, the reaction chamber comprises: a pressure greater than or equal to 13 pascals and less than or equal to 2666 pascals; and a temperature greater than or equal to 60 °C and less than or equal to 150 °C.

14. The method of claim 5, wherein in each of the second barrier layer ALD cycle and the second dielectric layer ALD cycle, the reaction chamber comprises: a pressure greater than or equal to 13 pascals and less than or equal to 2666 pascals; and a temperature greater than or equal to 60 °C and less than or equal to 150 °C.

15. The method of claim 1, wherein the at least one reflective core particle is selected from the group consisting of Au, Cu, Al, brass, bronze, TiN, Cr, stainless steel, aluminum oxide (AI2O3), silicon dioxide (SiO2), bismuth oxychloride, glass material, mica, and combinations thereof.

16. The method of claim 1, wherein the conformal dielectric layer is selected from the group consisting of TiO2, ZnS, ZrO2, HfO2, Fe3O4, AlAs, Fe2O3, PbS, GaAs, InAs, SiO2, MgF2, KBr, ZnO, AI2O3, and combinations thereof; the conformal barrier layer is selected from the group consisting of AI2O3, SiO2, MgF2, KBr, ZnO, and combinations thereof; and the conformal absorption layer is selected from the group consisting of W, Cr, Ge, Ni, stainless steel, Pd, Ti, Si, V, TiN, Co, Mo, Nb, iron oxides, and combinations thereof.

17. The method of claim 4, wherein the conformal outer protective layer is selected from the group consisting of SiO2, AI2O3, organosilanes, organophosphines, phosphates, and combinations thereof.

18. The method of claim 5, wherein the second conformal barrier layer is selected from the group consisting of AI2O3, SiO2, MgF2, KBr, ZnO, and combinations thereof; and the second conformal dielectric layer is selected from the group consisting of TiO2, ZnS, ZrO2, HfO2, Fe3O4, AlAs, Fe2O3, PbS, GaAs, InAs, SiO2, MgF2, KBr, ZnO, AI2O3, and combinations thereof.

19. The method of claim 6, wherein the conformal outer protective layer is selected from the group consisting of SiO2, AI2O3, organosilanes, organophosphines, phosphates, and combinations thereof.

20. The method of claim 1, wherein the conformal dielectric layer has a thickness greater than or equal to 5 nm and less than or equal to 500 nm; the conformal barrier layer has a thickness less than or equal to 50 nm; and the conformal absorption layer has a thickness greater than or equal to 2 nm and less than or equal to 50 nm.

21. The method of claim 5, wherein the second conformal barrier layer has a thickness less than or equal to 50 nm; and the second conformal dielectric layer has a thickness greater than or equal to 5 nm and less than or equal to 500 nm. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

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