Three-dimensional metamaterial structure and low-temperature electron beam processing method and application thereof

Abstract

The present application relates to a kind of three-dimensional metamaterial structures and its low-temperature electron beam processing method and application, three-dimensional metamaterial structure includes the metal reflection layer, transmission medium layer, multiple metal connecting layer and multiple metal micropillar group arranged in turn from bottom to top;Three-dimensional metamaterial structure is applied in the refractive index sensor in middle infrared wave band.The present application utilizes the two cycles of low-temperature electron beam exposure-electron beam evaporation process, i.e., can utilize a set of equipment, realizes the processing stacking of multilayer pattern under the premise of single sample entry and exit, forms three-dimensional metamaterial structure with closely connected interlayer connection and high structural strength, and the process utilizes water vapor to condense into amorphous ice layer as the mask of patterning processing, all raw materials are non-toxic and harmless, and the material and structure of three-dimensional metamaterial structure are simple, minimum line width is larger, reduces the requirement of processing precision, also can utilize the method to carry out the height regulation of metal micropillar group, greatly improves sensing sensitivity.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of mid-infrared refractive index sensors, in particular to a three-dimensional metamaterial structure and a low-temperature electron beam processing method and application thereof. BACKGROUND

[0002] The refractive index sensor based on metamaterials usually utilizes the surface plasmon resonance (SPR) effect of metal micro-nano structures, and can produce resonance absorption peaks in a specific waveband of the spectrum. These absorption peaks are often sensitive to changes in the environmental refractive index, so they can monitor the concentration, purity and other information of the test environment in real time, have the characteristics of miniaturization and high precision, and have great application potential in biological sensing, macromolecule detection and other aspects. From the perspective of practical application, an ideal refractive index sensor not only needs to work in a suitable waveband, but also needs to have high refractive index sensitivity and anti-interference ability, and a simple structure and a simple synthesis method can greatly improve the practical value of the sensor.

[0003] A micro-nano refractive index sensor based on metamaterials is disclosed in Chinese Patent No. CN113310946B, which comprises sensor units arranged in an equidistant array, the sensor units comprising a first metal layer, a first Bragg reflector, a dielectric layer, a second Bragg reflector and a second metal layer arranged from top to bottom, the first Bragg reflector and the second Bragg reflector each comprising a GaAs layer and an AlGaAs layer, the GaAs layer and the AlGaAs layer being periodically and alternately arranged, the sensor units being provided with through holes, the through holes being square.

[0004] Firstly, in terms of shape structure, the above-mentioned sensor is composed of periodically arranged square through holes, and the minimum structure line width is only 86nm, which requires high equipment precision and is not conducive to mass production. Secondly, in terms of thin film material, the above-mentioned sensor adopts a five-layer structure from top to bottom, wherein the two Bragg reflectors are each composed of six thin films, and these thin films involve four different materials of Ag, GaAs, AlGaAs and InGaAsP, and the layer structure and material composition are numerous, usually involving more than ten times of film plating and patterning steps, which not only makes the processing process complex and difficult, but also contains the toxic element As in the film composition, which is easy to cause serious harm to the human body during processing and use. Finally, in terms of sensing performance, the above-mentioned sensor exhibits low maximum sensing performance and sensitivity, and the optimal detection sensitivity is only 340nm / RIU. Therefore, these factors jointly limit the practical value of the sensor.

[0005] Three-dimensional metamaterial structures have higher design dimensions, which enable them to be processed into more complex metamaterial structures, thereby achieving a variety of functions that two-dimensional metamaterials cannot achieve. However, the preparation process of traditional three-dimensional micro-nano devices often relies on the internal stress of the material itself to achieve curling, as described below, which causes the device to have poor structural stability due to the inherent stress effect, making it difficult to be applied to actual scenarios such as biosensing. In addition, this processing method has poor controllability and low success rate, making it difficult to achieve mass replication.

[0006] A vortex light generator based on fractal nanocut paper and a preparation method thereof are disclosed in Chinese Patent Publication No. CN115793126A. The vortex light generator includes a peripheral fixed part, a central circular plane, and a plurality of fractal coiled units. The fractal coiled units connect the central circular plane and the peripheral fixed part. The plurality of fractal coiled units are evenly distributed around the central circular plane, and the number of fractal coiled units is even. The fractal coiled units are nanocut paper structures. When the central plane area supported by the fractal coiled units is driven by an external field, it deforms up and down, and becomes a three-dimensional state after deformation. A plurality of through holes are formed on the central circular plane. After the incident circularly polarized light passes through the vortex light generator, the spin angular momentum of the light is converted into orbital angular momentum to generate vortex light.

[0007] A terahertz metamaterial based on a three-dimensional reconfigurable open resonant ring of vanadium dioxide is disclosed in Chinese Patent Publication No. CN115864001A. The terahertz metamaterial includes a high-resistance silicon wafer substrate, a three-dimensional open resonant ring formed on the substrate as a structural unit, and a two-dimensional array composed of resonant rings in the radial and axial directions. Each structural unit has a lower layer of vanadium dioxide film and an upper layer of gold film. The three-dimensional structure is curled from the double-layer strip of vanadium dioxide and gold film. The strip length is 100-150 μm, and the width is 10-20 μm. The three-dimensional structure curled from the double-layer strip is a three-dimensional open resonant ring. At room temperature, the initial resonant ring opening corresponds to a central angle of 300-320 degrees. In the two-dimensional array, the row distance is 5-10 μm, and the column distance is 10-30 μm. The gold film realizes specific peak resonance absorption, and the vanadium dioxide film phase transition adjusts the resonant ring opening angle, thereby dynamically modulating the terahertz resonance wavelength.

[0008] A three-dimensional ring magnetic dipole device and a preparation method thereof are disclosed in Chinese Patent Publication No. CN106785294A. The device is formed by an array of multiple structural units. Each structural unit includes: a self-supporting insulating medium film serving as a support base; a plurality of overhanging portions, which are cut and folded from the self-supporting insulating medium film, have an even number and are not less than four, are fixed to the same side of the self-supporting insulating medium film, and form an angle between the corresponding overhanging portion and the self-supporting insulating medium film; and a metal open resonant ring, which has the same number as the overhanging portions, is arranged on the side surface of the overhanging portions one by one, is used for binding a magnetic field, and generates a magnetic dipole. The magnetic dipoles are connected end to end to form a closed loop, and the closed loop is used to realize ring magnetic dipole resonance.

[0009] At present, a variety of three-dimensional metamaterial structures have been developed based on surface stress or using advanced technical means such as electron beam bombardment to fold and curl. Although these devices manufactured by fine processing technology have unique physical properties in theory, they all face a common problem in practical application: due to the intrinsic stress effect, these devices are prone to collapse, resulting in poor structural stability. In addition, in the process of patterning these structures, toxic organic photoresist is usually used as a mask for pattern transfer. This approach not only increases the danger of the production process, but also easily leads to the residue of toxic substances, posing a threat to the environment and the health of the operators. At the same time, the controllability of the curling and folding process is poor, and the success rate is low, which makes it extremely difficult to mass replicate these complex three-dimensional structures. All these factors combined together greatly limit the practical application potential of such three-dimensional metamaterial structures in the fields of biosensing, microelectronics and other high-tech applications. SUMMARY

[0010] In view of the deficiencies of the prior art, the first object of the present application is to provide a three-dimensional metamaterial structure which has the advantages of simple structure and material and high sensitivity.

[0011] The second object of the present application is to provide a low-temperature electron beam processing method for a three-dimensional metamaterial structure which has the advantages of simple processing and suitability for mass production.

[0012] The third object of the present application is to provide an application of a three-dimensional metamaterial structure which has the advantages of working in the 7-10 μm wave band, strong anti-interference ability, high sensitivity and suitability for the field of biosensing.

[0013] To achieve the above-mentioned first object, the present application provides the following technical solutions:

[0014] A three-dimensional metamaterial structure, comprising, from bottom to top, a metal reflection layer, a transmission medium layer, a metal connecting layer, and a metal micropost group, the metal micropost group comprising a first metal micropost in the center and a plurality of second metal microposts arranged around the first metal micropost, and the metal connecting layer connecting the bottom of the first metal micropost and the second metal microposts, respectively.

[0015] Further, the metal of the metal reflection layer is Au or Ag.

[0016] And / or, the medium of the transmission medium layer is SiO2 or Al2O3.

[0017] And / or, the metal of the metal connecting layer is Au or Ag.

[0018] And / or, the metal of the metal micropost group is Au or Ag.

[0019] Still further, the orthographic projection of the metal reflection layer, the transmission medium layer, the first metal micropost and the second metal micropost in the vertical direction is circular or regular polygon, respectively, the orthographic projection of the metal connecting layer is radial from the first metal micropost to the plurality of second metal microposts, respectively, and the edges of the metal reflection layer and the transmission medium layer are approximately on the same side line.

[0020] Still further, the orthographic projection of the metal reflection layer, the transmission medium layer, the first metal micropost and the second metal micropost in the vertical direction is square, respectively.

[0021] Still further, the height h1 of the metal reflection layer is 0.1-0.2 μm, the height h2 of the transmission medium layer is 0.2-0.3 μm, the height h3 of the metal connecting layer is 0.1-0.2 μm, and the height h4 of the first metal micropost and the second metal micropost is 0.4-1.0 μm.

[0022] Still further, the height h1 of the metal reflection layer is 0.1 μm, the height h2 of the transmission medium layer is 0.2 μm, the height h3 of the metal connecting layer is 0.1 μm, and the height h4 of the first metal micropost and the second metal micropost is 0.6 μm.

[0023] Still further, the radius or opposite side distance P of the metal reflection layer and the transmission medium layer is 2.2-2.8 μm, the radial diameter L of the metal connecting layer is 2.0-2.5 μm, and the radius or opposite side distance w of the first metal micropost and the second metal micropost is 0.1-0.3 μm.

[0024] Further, the radius or opposite side distance P of the metal reflective layer and the transmission medium layer is 2.4 μm, the opposite side distance L of the metal micropillar group is 2.3 μm, and the radius or opposite side distance w of the first metal micropillar and the second metal micropillar is 0.2 μm.

[0025] To achieve the above-mentioned second object, the present application provides the following technical scheme.

[0026] A low-temperature electron beam processing method of a three-dimensional metamaterial structure, comprising the following steps,

[0027] S1, a substrate is prepared, and a metal reflective layer and a transmission medium layer are sequentially deposited on the surface of the substrate to obtain a first sample;

[0028] S2, the first sample is transferred into a mirror cavity of a field emission scanning electron microscope, a first amorphous ice layer is deposited on the surface of the transmission medium layer under a low-temperature condition, and then electron beam exposure is performed to remove the first amorphous ice layer in the structure region, and then the sample is transferred into an electron beam coating cavity, a metal connecting layer is deposited on the surface of the transmission medium layer to obtain a second sample;

[0029] S3, the second sample is transferred into the mirror cavity of the field emission scanning electron microscope, a second amorphous ice layer is deposited on the surface of the metal connecting layer under a low-temperature condition, and then electron beam exposure is performed to remove the second amorphous ice layer in the structure region, and then the sample is transferred into the electron beam coating cavity, a metal micropillar group is deposited on the surface of the transmission medium layer to obtain a third sample;

[0030] S4, after the third sample is raised to room temperature, gas blowing is performed to remove the first amorphous ice layer, the second amorphous ice layer and the metal film in the non-structure region, and a three-dimensional metamaterial structure is obtained.

[0031] Further, in the S1, the metal reflective layer is deposited by one of electron beam evaporation, thermal evaporation and sputtering.

[0032] Further, in the S1, the transmission medium layer is deposited by one of electron beam evaporation, thermal evaporation and ion enhanced chemical vapor deposition (PECVD).

[0033] Further, in the S2 and S3, the low-temperature condition is a temperature condition equal to or lower than the sublimation point of water vapor under the corresponding gas pressure, and the first amorphous ice layer and the second amorphous ice layer are respectively solid films formed by sublimation of water vapor.

[0034] Further, in the S2 and S3, the height of the first amorphous ice layer exceeds the total height of the metal connecting layer and the metal micropillar group, and the height of the second amorphous ice layer exceeds the height of the metal micropillar group.

[0035] Further, in the S2 and S3, the electron beam energy of the electron beam exposure is 1-30 keV, the electron area dose is 0.1-5.0 C / cm 2 , and the electron beam spot step is 0.001-0.100 mu m.

[0036] Further, in the S2, the method for depositing the metal connection layer is one of electron beam evaporation, thermal evaporation and sputtering.

[0037] Further, in the S3, the method for depositing the metal micro pillar group is one of electron beam evaporation, thermal evaporation and sputtering.

[0038] To achieve the above-mentioned third object, the application provides the following technical scheme.

[0039] Application of a three-dimensional metamaterial structure in a middle infrared wave band refractive index sensor.

[0040] In summary, the beneficial technical effects of the application are:

[0041] The metal reflection layer, the metal connection layer and the metal micro pillar group of the three-dimensional metamaterial structure are composed of the same metal material, wherein the metal reflection layer functions to reflect incident light and enhance a detection signal, the transmission medium layer functions to avoid contact short circuit between upper and lower layer structures and has relatively high transmittance, and the metal connection layer and the metal micro pillar group are resonance units, under the excitation of incident light, free electrons on the surface of the resonance units form collective oscillation at the interface between the metal and the medium, when the oscillation frequency is the same as the frequency of the evanescent wave generated by total reflection at the interface, resonance absorption effect, i.e., surface plasmon resonance (SPR), is generated, and then a wave trough (dip) of resonance absorption is formed at a specific wavelength of the reflection spectrum; the wavelength position corresponding to the dip is closely related to the refractive index of the environment in which the resonance unit is located, when the environmental refractive index increases, the dip moves to a larger wavelength (red shift), and then the contact area of the detection object and the sensor is greatly increased, and the dipole resonance effect is enhanced, so that the detection sensitivity and other performance indicators are significantly improved, and the height of the metal micro pillar group has a great influence on the sensitivity.

[0042] The three-dimensional metamaterial structure of the present application can be used in actual use, and the to-be-detected substance can be coated or dripped on the surface of the sensor, or the sensor can be placed in the to-be-detected liquid environment, and the spectrum of the sensor is tested by a Fourier infrared spectrometer (FTIR) or a similar spectral analysis instrument. A plurality of known refractive index materials can be tested first to obtain the corresponding relationship between the wavelength at the dip and the refractive index, which is used as standard data. Then, the to-be-detected substance is tested, and the refractive index of the to-be-detected substance can be read from the standard data, and the composition, concentration and other information of the to-be-detected substance can be analyzed. In the detection of biological substances such as exosomes and the like, the three-dimensional metamaterial structure can also effectively capture and fix micron-sized biological macromolecules or organelles, thereby ensuring the stability of the detection signal.

[0043] The three-dimensional metamaterial structure of the present application has good structural stability. The sensor is repeatedly cleaned several times in a liquid environment such as pure water, ethanol and acetone at a temperature of 20-80℃ and a frequency of 40KHz for 5 minutes each time. The three-dimensional metamaterial structure is still intact and undamaged as shown by atomic force microscopy (AFM), which proves the stability of the sensor in a liquid environment or a flowing state.

[0044] The method of the present application uses two cycles of low-temperature electron beam exposure and electron beam evaporation processes to realize the processing and stacking of multiple layers of patterns in a single sample loading and unloading process using a single set of equipment, thereby forming a three-dimensional metamaterial structure with tight interlayer connection and high structural strength. In this process, water vapor is condensed into an amorphous ice layer to serve as a mask for patterned processing, without introducing any toxic organic photoresist. All raw materials are non-toxic and harmless. The material and structure of the three-dimensional metamaterial structure are simple, and the minimum line width is more than 200nm, which reduces the requirement for processing precision. The method can also be used for height regulation of the metal micropillar group, which can improve the sensing sensitivity from 1740nm / RIU to 3580-5800nm / RIU, greatly improving the sensing sensitivity.

[0045] The application of the three-dimensional metamaterial structure in the present application in a mid-infrared waveband refractive index sensor works in the mid-infrared waveband, and the low energy of the mid-infrared light does not produce harmful ionizing radiation to biological samples. The specific working wavelength range is between 7 and 10 microns, which does not produce harmful ionizing radiation to biological organisms. The main absorption peaks of water molecules hydrogen bonds in the infrared and terahertz wavebands are effectively avoided, thereby avoiding the interference of irrelevant signals in the to-be-detected substance containing water. Therefore, the sensor also has the characteristics of non-ionizing radiation and strong anti-interference ability, and is very suitable for use in the field of biological sensing. BRIEF DESCRIPTION OF DRAWINGS

[0046] Figure 1 is a schematic diagram of the three-dimensional metamaterial structure of embodiment 1 of the present application.

[0047] Figure 2 is a front view structural schematic diagram of the three-dimensional metamaterial structure of embodiment 1 of the present application.

[0048] Figure 3 is a reflection spectrum diagram of embodiment 1 of the present application.

[0049] Figure 4 is a flow chart of the method provided by embodiment 2 of the present application.

[0050] Figure 5 is an AFM diagram of the three-dimensional metamaterial structure of embodiment 2 of the present application.

[0051] Figure 6 is a sensor sensitivity detection diagram of embodiment 3 of the present application.

[0052] In the figure, 1, metal reflection layer; 2, transmission medium layer; 3, metal connecting layer; 4, metal micropillar group. DETAILED DESCRIPTION

[0053] In order to make the technical means, creative features, purposes and effects of the present application more clear and easy to understand, the present application is further described below in combination with the drawings and specific embodiments.

[0054] Embodiment 1: Refer to Figure 1 A three-dimensional metamaterial structure disclosed by the present application comprises, from bottom to top, a metal reflection layer 1, a transmission medium layer 2, a metal connecting layer 3, and a metal micropillar group 4. The metal micropillar group 4 comprises a first metal micropillar at the center and four second metal micropillars arranged around the first metal micropillar, and the metal connecting layer 3 connects the bottom of the first metal micropillar and the second metal micropillars respectively. The orthographic projection of the metal reflection layer 1, the transmission medium layer 2, the first metal micropillar and the second metal micropillar in the vertical direction is a square respectively, the orthographic projection of the metal connecting layer 3 in the vertical direction is a cross-shaped radiation shape radiating from the first metal micropillar to the four second metal micropillars respectively, and the edges of the metal reflection layer 1 and the transmission medium layer 2 are approximately on the same side line.

[0055] Refer to Figure 2 In order to obtain the optimal sensor performance, the metal of the metal reflection layer 1, the metal connecting layer 3 and the metal micropillar group 4 is Au, and the medium of the transmission medium layer 2 is SiO2. At the same time, the height h1 of the metal reflection layer 1 is 0.1 μm, the height h2 of the transmission medium layer 2 is 0.2 μm, the height h3 of the metal connecting layer 3 is 0.1 μm, and the height h4 of the first metal micropillar and the second metal micropillar is 0.6 μm. The opposite side distance P of the metal reflection layer 1 and the transmission medium layer 2 is 0.6 μm. x =P y= 2.4 pm, the radiating diameter of the metal connecting layer 3 is L1 = L2 = 2.3 pm, and the opposite side distance of the first and second metal micropillars is w1 = w2 = 0.2 pm.

[0056] From Figure 3 It can be seen that the refractive index sensitivity of the three-dimensional metamaterial structure of the embodiment is 3580 nm / RIU, which can be obtained by reading the wavelength value at the highest refractive index n and absorption.

[0057] Embodiment 2: with reference to Figure 4 A low-temperature electron beam processing method of a three-dimensional metamaterial structure is disclosed in the present application, which is different from embodiment 1 in that it comprises the following steps,

[0058] S1 prepares a substrate (usually single crystal Si), and then forms a metal reflecting layer 1 and a transmission medium layer 2 on the surface of the substrate in sequence to obtain a first sample;

[0059] The metal reflecting layer 1 is deposited by electron beam evaporation, and the deposition rate is 0.040 nm / s.

[0060] The transmission medium layer 2 is deposited by electron beam evaporation, and the deposition rate is 0.025 nm / s.

[0061] S2 first transfers the first sample into the mirror cavity of the field emission scanning electron microscope, then deposits a first amorphous ice layer on the surface of the transmission medium layer 2 under low-temperature conditions, then electron beam exposure is performed to remove the first amorphous ice layer in the structure area, then it is transferred into the electron beam coating cavity to deposit a metal connecting layer 3 on the surface of the transmission medium layer 2 to obtain a second sample;

[0062] The low-temperature condition is a temperature condition equal to or lower than the sublimation point of water vapor at the corresponding gas pressure;

[0063] The first amorphous ice layer is a solid film formed by sublimation of water vapor, and the height of the first amorphous ice layer exceeds the total height of the metal connecting layer 3 and the metal micropillar group 4;

[0064] The electron beam energy of the electron beam exposure is 5 keV, the electron area dose is 0.5 C / cm 2 , and the electron beam spot step is 0.008 pm.

[0065] The metal connecting layer 3 is deposited by electron beam evaporation, and the deposition rate is 0.040 nm / s.

[0066] S3 first transfers the second sample into the mirror cavity of the field emission scanning electron microscope, then deposits the second amorphous ice layer on the surface of the metal connecting layer 3 under low temperature conditions, and then exposes to the electron beam to remove the second amorphous ice layer in the structure area, and then transfers into the electron beam coating cavity to deposit the metal micropillar group 4 on the surface of the transmission medium layer 2, to obtain a third sample;

[0067] The low temperature condition is a temperature condition equal to or lower than the sublimation point of water vapor under the corresponding air pressure;

[0068] The second amorphous ice layer is a solid film formed after the sublimation of water vapor, and the height of the second amorphous ice layer exceeds the height of the metal micropillar group 4;

[0069] The electron beam energy of the electron beam exposure is 5 keV, the electron area dose is 0.9 C / cm 2 , and the electron beam spot step length is 0.008 μm.

[0070] The deposition of the metal micropillar group 4 is performed by electron beam evaporation, and the deposition rate is 0.040 nm / s.

[0071] S4 blows the third sample to room temperature with nitrogen or compressed air to remove the first amorphous ice layer, the second amorphous ice layer and the metal film in the non-structure area, to obtain a three-dimensional metamaterial structure.

[0072] From Figure 5 It can be seen that the three-dimensional metamaterial structure prepared in the embodiment has good structural stability. Specifically, using an ultrasonic cleaning machine, the sensor is repeatedly cleaned several times in a liquid environment of pure water, ethanol and acetone, at a temperature of 20-80°C and a frequency of 40KHz, each time for 5 minutes. By atomic force microscope (AFM) means, the three-dimensional metamaterial structure is still intact, which proves the stability of the sensor working in a liquid environment or a flowing state.

[0073] Example 3: Application of the three-dimensional metamaterial structure disclosed in the present application in a mid-infrared waveband refractive index sensor, which is different from example 1 in that the height h4 of the first metal micropillar and the second metal micropillar is 0-1.0 μm.

[0074] From Figure 6 It can be seen that the height of the metal micropillar group 4 has a great influence on the sensitivity. When h4 is 0 μm, the three-dimensional metamaterial structure is equivalent to a two-dimensional planar structure, and the sensitivity is only about 1740 nm / RIU. When h4 rises to 0.6 μm as shown in example 1, the sensitivity is 3580 nm / RIU. When h4 rises to 1 μm, the sensitivity can rise to 5800 nm / RIU. The above all proves the effect of the three-dimensional metamaterial structure on the improvement of the performance of the sensor.

[0075] In addition, the sensor of the embodiment works in the mid-infrared waveband, and the mid-infrared light energy is low, which will not produce harmful ionizing radiation to the biological sample. The specific working wavelength range is between 7 and 10 μm, which effectively avoids the main absorption peak of the hydrogen bond of water molecules in the infrared and terahertz waveband, and further avoids the interference of irrelevant signals in the water-containing measured object. Therefore, the sensor also has the characteristics of non-ionizing radiation and strong anti-interference ability, and is very suitable for the field of biological sensing.

[0076] Finally, it should be pointed out that the above embodiments are only used to illustrate the technical solutions of the present application but not limit the present application. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the present application, and all should be covered in the scope of the claims of the present application.

Claims

1. A three-dimensional metamaterial structure, characterized in that: It includes a metal reflective layer (1), a transmission medium layer (2), a metal connecting layer (3), and a metal micropillar group (4) arranged sequentially from bottom to top. The metal micropillar group (4) includes a first metal micropillar located at the center and a plurality of second metal micropillars arranged around the first metal micropillar. The metal connecting layer (3) connects the bottom of the first metal micropillar and the second metal micropillar respectively.

2. The three-dimensional metamaterial structure according to claim 1, characterized in that: The metals of the metal reflective layer (1), the metal connecting layer (3), and the metal micron column group (4) are Au or Ag, and the medium of the transmission medium layer (2) is SiO2 or Al2O3.

3. The three-dimensional metamaterial structure according to claim 2, characterized in that: The metal reflective layer (1), the transmission medium layer (2), the first metal micropillar and the second metal micropillar are each independently circular or regular polygonal in the vertical direction. The metal connecting layer (3) is radially projected from the first metal micropillar to multiple second metal micropillars in the vertical direction. The edges of the metal reflective layer (1) and the transmission medium layer (2) are approximately on the same sideline.

4. A three-dimensional metamaterial structure according to claim 3, characterized in that: The height h of the metal reflective layer (1) is 0.1~0.2μm, the height h2 of the transmissive medium layer (2) is 0.2~0.3μm, the height h3 of the metal connecting layer (3) is 0.1~0.2μm, and the height h4 of the first metal micropillar and the second metal micropillar is 0.4~1.0μm.

5. A three-dimensional metamaterial structure according to claim 3, characterized in that: The radius or side-to-side distance P of the metal reflective layer (1) and the transmission medium layer (2) is 2.2~2.8μm, the radiation diameter L of the metal connecting layer (3) is 2.0~2.5μm, and the radius or side-to-side distance w of the first metal micropillar and the second metal micropillar is 0.1~0.3μm.

6. A method for low-temperature electron beam fabrication of a three-dimensional metamaterial structure according to any one of claims 1 to 5, characterized in that: Includes the following steps, S1 Prepare a substrate, and first deposit a metal reflective layer (1) and a transmission medium layer (2) sequentially on the surface of the substrate to obtain the first sample; S2 first transfers the first sample into the cavity of the field emission scanning electron microscope, and then deposits a first amorphous ice layer on the surface of the transmission medium layer (2) under low temperature conditions. Then, electron beam exposure is used to remove the first amorphous ice layer in the structural region. Then, it is transferred to the electron beam coating cavity and a metal bonding layer (3) is deposited on the surface of the transmission medium layer (2) to obtain the second sample. S3 first transfers the second sample into the cavity of the field emission scanning electron microscope, and then deposits a second amorphous ice layer on the surface of the metal bonding layer (3) under low temperature conditions. Then, electron beam exposure is used to remove the second amorphous ice layer in the structural region. Then, it is transferred to the electron beam coating cavity and a metal micropillar group (4) is deposited on the surface of the transmission medium layer (2) to obtain the third sample. After raising the third sample to room temperature, S4 purged it with gas to remove the first amorphous ice layer, the second amorphous ice layer, and the metal film from the unstructured region, thus obtaining a three-dimensional metamaterial structure.

7. The method for low-temperature electron beam fabrication of a three-dimensional metamaterial structure according to claim 6, characterized in that: In S2 and S3, the low-temperature condition is a temperature condition equal to or lower than the sublimation point of water vapor at the corresponding pressure, and the first amorphous ice layer and the second amorphous ice layer are solid films formed by the sublimation of water vapor.

8. The method for low-temperature electron beam fabrication of a three-dimensional metamaterial structure according to claim 7, characterized in that: In S2 and S3, the height of the first amorphous ice layer exceeds the total height of the metal connecting layer (3) and the metal micron column group (4), and the height of the second amorphous ice layer exceeds the height of the metal micron column group (4).

9. The low-temperature electron beam fabrication method for a three-dimensional metamaterial structure according to claim 6, characterized in that: In S2 and S3, the electron beam energy for controlling electron beam exposure is 1~30 keV, and the electron area dose is 0.1~5.0 C / cm². 2 The electron beam spot size is 0.001~0.100μm.

10. The application of a three-dimensional metamaterial structure according to any one of claims 1 to 5 in a mid-infrared refractive index sensor.

Images