Metal nanoring optical antenna and preparation method thereof

Abstract

The invention relates to a metal nanoring optical antenna and a forming method thereof, and the method comprises the steps: arranging a glue material on a substrate, imaging the glue material, and then carrying out the reaction etching of the substrate according to a pattern, and forming a nanorod with an inclined side wall; soaking by using an organic solvent to remove the glue material above the nano-column; depositing a plasmon material film on the surface of the nanorod and the surface of the substrate; and removing the plasmon material on the top of the nanorod and the surface of the substrate, and reserving the plasmon material on the side wall of the nanorod to form the nanoring. A plasmon closed metal ring is formed on the side wall of the nanorod, and a shape with a narrow upper part and a wide lower part is formed by regulating and controlling the etching process of the nanorod. Nanopillar-based metal nanoring preparation and patterning do not use electron beam lithography or other lithography techniques, but mainly use metal sputtering and ion beam etching methods. The inclination angle of the side wall, the thickness of the ring wall and the metal material of the nanoring can be adjusted by the process.

Description

Technical Field

[0001] The present invention relates to the technical field of nano-optical antennas, and in particular to a metal nano-ring optical antenna and a preparation method thereof. Background Art

[0002] Nano-optical antennas are devices that convert between freely propagating light fields and localized energy. Their working principle is to effectively couple optical frequency electromagnetic waves into sub-wavelength devices based on the surface plasmon resonance effect, localize the energy in the near-field region of the optical antenna, greatly enhance the local field effect, modulate the radiation of point light sources and control the radiation field at the nanoscale. Among them, metal nanorings have a local lens effect, which can radiate light signals in a direction and improve the extraction efficiency of single-photon radiation sources. The resonant wavelength of the nanoring can be adjusted by changing the wall thickness of the ring, which is determined by the electromagnetic coupling between the inner and outer ring surfaces. Nano-optical antennas can be used to enhance biochemical molecular medical sensing, solar energy devices, and optical nano-trapping.

[0003] Electron beam lithography (EBL) is often used to prepare metal nanorings. In addition to the easy control of the diameter, height and lattice constant of the array, the lattice type of the array is also easy to control, but electron beam lithography is costly and time-consuming, making it difficult to prepare on a large scale. In addition, low-cost colloidal lithography, nanoimprinting and block copolymer-based methods combined with electroplating and metal particle self-assembly processes have been developed for the preparation of large-area nanoring arrays. However, most of these methods can only control the diameter and lattice constant of the nanoring array, and it is difficult to adjust the height of the nanoring and prepare multi-layer or multi-material concentric nanoring optical antennas, and it is difficult to form nanorings with tilt angles. Summary of the invention

[0004] In order to solve at least part of the above problems in the prior art, the present invention provides a method for forming a metal nano-ring optical antenna, comprising:

[0005] Arranging a glue material on a substrate, patterning the glue material, and then using a reactive etching method to form a nanocolumn with an inclined side wall according to the pattern;

[0006] Soaking with an organic solvent to remove the glue material on the nanorods;

[0007] Depositing a thin film of plasmon material on the surface of the nanorods and the surface of the substrate; and

[0008] The plasmon material on the top of the nanopillar and the surface of the substrate is removed, and the plasmon material on the sidewall of the nanopillar is retained to form a nanoring.

[0009] Furthermore, by repeating the plasmon material thin film deposition step and the nano-ring formation step, mixed metal nano-rings of different materials can be obtained on the sidewalls of the nano-pillars.

[0010] Further, the substrate is etched using a reactive ion etching method or an ion beam etching method to form a nanocolumn with an inclined sidewall;

[0011] Plasmonic material deposition is performed using a sputtering process.

[0012] Furthermore, when depositing the plasmon material film, the material deposition direction is mainly normal incidence, and there is also oblique incidence; and / or

[0013] An ion beam etching process is performed in a direction perpendicular to the plane to remove the plasmon material on the top of the nanopillar and the surface of the substrate, forming a metal nanoring supported by the nanopillar to form a nanoantenna.

[0014] Furthermore, the material of the nano-ring is a plasmon metal material; and / or

[0015] The materials of the multiple layers of nanorings are different; and / or

[0016] The nanocolumn has an inclined side wall and a round top, and is narrow at the top and wide at the bottom.

[0017] The present invention also provides a metal nano-ring optical antenna, comprising a substrate and one or more metal nano-ring units located on the substrate, wherein the metal nano-ring units include:

[0018] Nanopillars: and

[0019] One or more layers of nanorings are located on the sidewalls of the nanocolumns.

[0020] Furthermore, the nanocolumn has an inclined side wall and a round top, and the nanocolumn is narrow at the top and wide at the bottom.

[0021] Furthermore, the material of the nano-ring is a plasmon metal material; and / or

[0022] The materials of the multi-layer nanorings are different.

[0023] Furthermore, the materials of the nanorods and the substrate are non-metallic materials.

[0024] The present invention also provides a method for chemical and / or biological detection using a metal nanoring optical antenna, comprising:

[0025] Antibodies, antigens, and compound molecules are fixed on the surface of the metal nano-ring optical antenna to perform biological and / or chemical molecule detection.

[0026] The present invention has at least the following beneficial effects: The present invention proposes a metal nanoring optical antenna and a method for forming the same, wherein a closed metal ring of plasmons is formed on the side wall of a nanocolumn, and the nanocolumn etching process is regulated to form a shape that is narrow at the top and wide at the bottom. The inner and outer surfaces of this nanoantenna can gather electromagnetic fields, increase the spatial distribution of hot spots, and control the directivity of emitted light. The resonant wavelength can be adjusted by changing its size (such as diameter, height, and lattice constant) and metal material. The preparation and patterning of metal nanorings based on nanocolumns do not use electron beam lithography or other lithography techniques, but mainly use metal sputtering and ion beam etching methods. The side wall inclination angle, ring wall thickness, and metal material of the nanoring can be adjusted by the above process. The method of the present invention is low in cost and can be used to prepare metal nanoring optical antennas on a large scale. The method of the present invention can prepare concentric nanoring optical antennas of multiple layers or multiple materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to further illustrate the above and other advantages and features of various embodiments of the present invention, a more specific description of various embodiments of the present invention will be presented with reference to the accompanying drawings. It will be understood that these drawings only depict typical embodiments of the present invention and are therefore not to be considered as limiting the scope thereof. In the accompanying drawings, for clarity, identical or corresponding parts will be represented by identical or similar reference numerals.

[0028] Figure 1 shows a top view of a metal nanoring unit according to one embodiment of the present invention;

[0029] Figure 2 shows a perspective view of a metal nanoring unit according to one embodiment of the present invention;

[0030] Figure 3 shows a cross-sectional view of a metal nanoring unit according to one embodiment of the present invention;

[0031] Figures 4 to 9 A schematic diagram showing a process of forming a metal nano-ring optical antenna according to an embodiment of the present invention is shown;

[0032] Fig.10 The extinction rate simulation results of the metal nano-ring optical antenna with different tilt angles according to one embodiment of the present invention are shown. DETAILED DESCRIPTION

[0033] It should be noted that various components in the various drawings may be shown exaggeratedly for illustrative purposes and are not necessarily correct to scale.

[0034] In the present invention, each embodiment is only intended to illustrate the aspects of the present invention and should not be construed as limiting.

[0035] In the present invention, unless otherwise specified, the quantifiers "a", "an" and "an" do not exclude the presence of a plurality of elements.

[0036] It should also be pointed out that in the embodiments of the present invention, for the sake of clarity and simplicity, only a portion of the parts or components may be shown, but a person of ordinary skill in the art will understand that under the teachings of the present invention, required parts or components may be added as needed in specific scenarios.

[0037] It should also be pointed out that within the scope of the present invention, the terms "same", "equal", "equal to" and the like do not mean that the two values ​​are absolutely equal, but allow a certain reasonable error, that is, the terms also cover "substantially the same", "substantially equal", and "substantially equal to".

[0038] It should also be pointed out that in the description of the present invention, the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than explicitly or implicitly indicating that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as explicitly or implicitly indicating relative importance.

[0039] In addition, the embodiments of the present invention describe the process steps in a specific order, but this is only for the convenience of distinguishing the steps, and does not limit the sequence of the steps. In different embodiments of the present invention, the sequence of the steps can be adjusted according to the adjustment of the process.

[0040] Figure 1 shows a top view of a metal nanoring unit according to one embodiment of the present invention; Figure 2 shows a perspective view of a metal nanoring unit according to one embodiment of the present invention; Figure 3 A cross-sectional view of a metal nanoring unit according to an embodiment of the present invention is shown.

[0041] like Figures 1 to 3 As shown, a metal nano-ring optical antenna includes a substrate 10 and one or more metal nano-ring units 20 located on the substrate.

[0042] The substrate 10 may be made of non-metallic materials such as silicon dioxide, silicon, or glass.

[0043] The plurality of metal nano-ring units 20 are arranged at a specific period, and may be arranged to form, but not limited to, a square array, a hexagonal array, a circular array or other symmetrical arrays, to form a nano-antenna array structure.

[0044] The metal nanoring unit 20 includes a nanocolumn 21 and a closed layer or layers of nanorings 22 located on the inclined sidewalls of the nanocolumn. The nanocolumn 21 is a column with a round top and inclined sidewalls. The nanocolumn 21 can be made of non-metallic materials such as silicon dioxide, silicon, and glass. The nanoring 22 is narrow at the top and wide at the bottom as the sidewalls of the nanocolumn 21 are inclined. The materials of the nanoring 22 include, but are not limited to, metal materials for excitons such as gold, silver, copper, and platinum. The materials of the multilayer nanorings are different, and they are mixed metal nanorings.

[0045] The conventional metal nanoring is a vertical metal ring having two resonance modes, antisymmetric dipole resonance and dipole resonance. The sidewall angle affects the effective area of ​​the antisymmetric dipole resonance domain, thereby adjusting its resonance wavelength. The nanoring of the present invention is an inclined metal ring that is narrow at the top and wide at the bottom. When the inclination angle reaches a certain size, for example, the inclination angle is about 10° (angle with the vertical direction), due to the large size difference between the top and bottom of the metal nanoring, the dipole resonance peak will split into two single peaks, increasing the applicable band and increasing the extinction rate, such as Fig.10 The simulation results are shown in Figure 2.

[0046] Figures 4 to 9 A schematic diagram of a formation process of a metal nanoring optical antenna according to an embodiment of the present invention is shown.

[0047] A method for forming a metal nano-ring optical antenna comprises:

[0048] Step 1, such as Figure 4 As shown, a glue material is arranged on a substrate 101, and the glue material is patterned to form a circular pattern 102, and then the substrate 101 is etched according to the circular pattern using reactive ion etching (RIE) or ion beam etching (IBE) to form a nano-pillar 103 with a tilted sidewall. Here, the nano-pillar 103 can be one or more, wherein the plurality of nano-pillars 103 can be arranged in a symmetrical array such as a square array, a hexagonal array, a circular array, etc. Here, the substrate 101 can be a non-metallic material such as silicon dioxide, silicon, quartz glass, etc. The glue material can be a nano-imprint glue, UV photoresist, etc.

[0049] The circular pattern 102 is formed by patterning the glue material using methods such as nanoimprint lithography, colloidal lithography or electron beam lithography.

[0050] The substrate 101 is dry-etched using methods including but not limited to reactive ion etching (RIE) or ion beam etching (IBE) to form nanorods or nanorod arrays.

[0051] Silicon dioxide etching uses a mixture of trifluoromethane, hexafluoroethane and argon. Fluorine-based gases mainly play a role in chemical etching, while argon plays a role in physical etching. The inclination of the nanocolumns can be controlled by adjusting the gas ratio and the etching environment pressure.

[0052] For example, the ratio of trifluoromethane, hexafluoroethane and argon is 28:31:34, the etching environment pressure is 0.9 Pa, and the inclination of the etched nanocolumns is 9°.

[0053] Step 2, such as Figure 5 As shown, the glue material above the nanorods is removed by soaking in an organic solvent, which may be acetone, ethanol, isopropanol, etc., and the soaking time may be 10 minutes.

[0054] Step 3, such as Figure 6 As shown, a plasmon material film 104 is deposited on the surface of the nanocolumn and the surface of the substrate. The nanocolumn is fully covered with plasmon material. The material deposition direction is mainly normal incidence, and there is also oblique incidence. The role of oblique incidence is to form a metal layer on the side wall of the nanocolumn. The material deposition direction is multi-directional, vertical and inclined. The deposition direction is mainly normal incidence. The metal deposited on the top of the nanocolumn is thicker than the metal deposited on the side wall of the nanocolumn. The plasmon material film is deposited with the nanocolumn as a supporting structure. The plasmon material can be a metal material for plasmons such as gold, silver, copper, platinum, etc. The thin film material is deposited by a sputtering process.

[0055] Step 4, such as Figure 7 As shown, the plasmon material on the top of the nanorod and the surface of the substrate is removed, and the plasmon material on the side wall of the nanorod is retained to form a nanoring 105. The plasmon material on the top of the nanorod and the surface of the substrate is removed by an ion beam etching process in a direction perpendicular to the plane to form a metal nanoring supported by the nanorod, thereby forming a nanoantenna.

[0056] The thickness of the metal on the sidewall of the nanocolumn is thinner than the top metal layer, and the inclination of the nanocolumn will affect the amount of metal etched on the sidewall. Since the etching direction is vertical, ion beam etching has good directionality. The larger the inclination angle of the nanocolumn sidewall, the more metal is etched on the sidewall. Therefore, it is necessary to control the inclination angle of the nanocolumn sidewall within a certain range, such as 7°, 9°, 10°, 11°, etc., to ensure that the amount of metal etched on the sidewall is less than that on the top layer. Moreover, during the etching of the top metal layer, secondary deposition of metal particles will occur, that is, the metal particles milled out from the top layer will fall on the sidewall of the nanocolumn, increasing the thickness of the metal on the sidewall in disguise. Therefore, when the inclination angle of the nanocolumn sidewall is controlled within a certain range, it can be ensured that while the metal on the top of the nanocolumn is removed, a metal layer is still left on the sidewall.

[0057] Step 5, such as Figure 8 and 9As shown, by repeating steps 3 and 4 to deposit a variety of plasmon thin film materials, mixed metal nanorings of different materials can be obtained on the sidewalls of the nanocolumns. The side surfaces of the nanocolumns have multiple layers of nanorings of different metals to form nanoantennas.

[0058] The invention proposes a metal nano-ring optical antenna and a method for forming the same, forming a closed metal ring of plasmons on the sidewall of the nano-pillar, and by regulating the etching process of the nano-pillar, forming a shape that is narrow at the top and wide at the bottom. The inner and outer surfaces of this nano-antenna can gather electromagnetic fields, increase the spatial distribution of hot spots, control the directivity of the emitted light, and adjust the resonant wavelength by changing its size (such as diameter, height and lattice constant) and metal material.

[0059] Metal nanoring optical antennas can be used in the fields of biological detection, light emitters, and photocatalysis.

[0060] In one embodiment of the present invention, when the metal nanoring optical antenna is used for biological detection, antibodies, antigens, compound molecules and other specific binding / adsorption sensitive molecules are fixed on the nanoring surface of the metal nanoring optical antenna to perform biological and chemical molecule detection. By methods including but not limited to chemical modification / cross-linking or molecular self-assembly, molecules with specific binding / adsorption properties of biological and chemical molecules, such as antibodies, antigens, DNA single strands, compounds, etc., are fixed on the nanoring surface to perform biological and chemical molecule detection. The fixation of molecules with specific binding / adsorption properties of biological and chemical molecules on the surface of the nanoring is not limited to direct fixation, and the two can be indirectly connected by cross-linking molecules or other intermediate layer molecules such as intermediate layer biochemical molecules.

[0061] Antibodies, antigens, compound molecules and other specific binding / adsorption sensitive molecules are fixed on the metal surface of the nanoantenna to enhance the spectral signals of biological / chemical molecules and improve detection sensitivity.

[0062] In one embodiment of the present invention, when the metal nano-ring optical antenna is applied to a light emitting device such as an LED / OLED, the metal nano-ring optical antenna is arranged at the front end of the light emitting device such as an LED / OLED, and the radiation efficiency of the light emitting device such as an LED / OLED is enhanced and the directionality of the emitted light is adjusted by the resonance effect of the nano-optical antenna.

[0063] The above-mentioned metal nanoring optical antenna can also be used in the field of photocatalysis to promote chemical reactions.

[0064] Although some embodiments of the present invention have been described in this application document, it will be appreciated by those skilled in the art that these embodiments are merely shown as examples. Those skilled in the art may conceive of numerous variations, alternatives, and improvements under the teachings of the present invention without departing from the scope of the present invention. The appended claims are intended to define the scope of the present invention and thereby cover methods and structures within the scope of these claims themselves and their equivalents.

Claims

1. A method for forming a metal nano-ring optical antenna, characterized in that: include: Arranging a glue material on a substrate, patterning the glue material, and then using a reactive etching method to form a nanocolumn with an inclined side wall according to the pattern; Soaking with an organic solvent to remove the glue material on the nanorods; Depositing a thin film of plasmon material on the surface of the nanorods and the surface of the substrate; and The plasmon material on the top of the nanopillar and the surface of the substrate is removed, and the plasmon material on the sidewall of the nanopillar is retained to form a nanoring.

2. The method according to claim 1, characterized in that By repeating the steps of depositing a thin film of a plasmon material and forming a nanoring, mixed metal nanorings of different materials can be obtained on the sidewalls of the nanocolumns.

3. The method according to claim 1, characterized in that Etching the substrate using a reactive ion etching method or an ion beam etching method to form a nanocolumn with an inclined sidewall; Plasmonic material deposition is performed using a sputtering process.

4. The method according to claim 1, characterized in that: When depositing a plasmon material film, the material deposition direction is mainly normal incidence, and there is also oblique incidence; and / or An ion beam etching process is performed in a direction perpendicular to the plane to remove the plasmon material on the top of the nanopillar and the surface of the substrate, forming a metal nanoring supported by the nanopillar to form a nanoantenna.

5. The method according to claim 2, characterized in that: The material of the nano ring is a plasmon metal material; and / or The materials of the multiple layers of nanorings are different; and / or The nanocolumn has an inclined side wall and a round top, and is narrow at the top and wide at the bottom.

6. A metal nano-ring optical antenna, characterized in that: The invention comprises a substrate and one or more metal nano-ring units located on the substrate, wherein the metal nano-ring units comprise: Nanopillars: and One or more layers of nanorings are located on the sidewalls of the nanocolumns.

7. The metal nanoring optical antenna according to claim 1, characterized in that: The nanocolumn has an inclined side wall and a round top, and is narrow at the top and wide at the bottom.

8. The metal nanoring optical antenna according to claim 1, characterized in that: The material of the nano ring is a plasmon metal material; and / or The materials of the multi-layer nanorings are different.

9. The metal nanoring optical antenna according to claim 1, characterized in that: The materials of the nanorods and the substrate are non-metallic materials.

10. A method for chemical and / or biological detection using the metal nanoring optical antenna according to any one of claims 6 to 9, comprising: Antibodies, antigens, and compound molecules are fixed on the surface of the metal nano-ring optical antenna to perform biological and / or chemical molecule detection.

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