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

Abstract

The invention relates to a three-dimensional metamaterial structure and a low-temperature electron beam processing method and application thereof. The three-dimensional metamaterial structure comprises a metal reflecting layer, a transmission dielectric layer, a plurality of metal connecting layers and a plurality of metal micron column groups which are sequentially arranged from bottom to top, the invention discloses application of a three-dimensional metamaterial structure in a mid-infrared band refractive index sensor. According to the invention, two cycles of a low-temperature electron beam exposure-electron beam evaporation process are utilized, namely, a set of equipment can be utilized to realize processing and stacking of multiple layers of patterns on the premise of single sample feeding and discharging, so that a three-dimensional metamaterial structure with tight interlayer connection and high structural strength is formed; in the process, water vapor is condensed into an amorphous ice layer to serve as a mask for patterning processing, all raw materials are nontoxic and harmless, the material and the structure of the three-dimensional metamaterial structure are simple, the minimum line width is large, the requirement for processing precision is lowered, the method can be used for adjusting and controlling the height of the metal micron column group, and the sensing sensitivity is greatly improved.

Description

Technical Field

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

[0002] Refractive index sensors based on metamaterials usually use effects such as surface plasmon resonance (SPR) of metal micro-nano structures to produce resonant absorption peaks in specific bands of the spectrum. These absorption peaks are often sensitive to changes in the refractive index of the environment, so they can monitor the concentration, purity and other information of the test environment in real time. They have the characteristics of miniaturization and high precision, and have great application potential in biosensing and macromolecular detection. From the perspective of practical applications, an ideal refractive index sensor not only needs to work in a suitable band, but also needs to have high refractive index sensitivity and anti-interference ability. In addition, simple structures and simple synthesis methods can greatly improve the practical value of the sensor.

[0003] A Chinese patent with authorization announcement number CN113310946B discloses a micro-nano refractive index sensor based on metamaterials, including sensor units arranged in an equidistant array, the sensor units including a first metal layer, a first Bragg reflector, a dielectric layer, a second Bragg reflector and a second metal layer arranged in sequence from top to bottom, the first Bragg reflector and the second Bragg reflector both including a GaAs layer and an AlGaAs layer, the GaAs layer and the AlGaAs layer are periodically alternately arranged, the sensor unit is provided with a through hole, and the through hole is square.

[0004] First, in terms of shape and structure, the above-mentioned sensor is composed of periodically arranged square through holes, and the minimum structural line width is only 86nm, which requires high equipment precision and is not conducive to mass production. Secondly, in terms of thin film materials, the above-mentioned sensor adopts a five-layer structure from top to bottom, among which the two layers of Bragg reflectors are composed of six layers of thin films, which involve four different materials: Ag, GaAs, AlGaAs, and InGaAsP. Its layer structure and material composition are numerous, usually involving more than a dozen coating and patterning steps, which not only makes the processing process complicated and difficult, but also contains toxic As elements in these thin film components, which can easily cause serious harm to the human body during processing and use. Finally, in terms of sensing performance, the highest sensing performance and sensitivity exhibited by the above-mentioned sensor are relatively low, 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 a higher design dimension, which enables them to be processed into more complex metamaterial structures, thereby realizing multiple 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, the devices caused by this processing method often have poor structural stability due to the inherent stress effect, which makes them difficult to be applied in practical 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 Chinese patent with publication number CN115793126A discloses a vortex light generator based on fractal nano-paper-cutting and a preparation method thereof, wherein the vortex light generator comprises a peripheral fixed portion, a central circular plane and a plurality of fractal winding units; the fractal winding unit connects the central circular plane with the peripheral fixed portion, and the plurality of fractal winding units are evenly distributed around the central circular plane, and the number of fractal winding units is an even number; the fractal winding unit is a nano-paper-cutting structure, and the fractal winding unit supports the central plane area to deform up and down when driven by an external field, and becomes a three-dimensional state after deformation; a plurality of through holes are provided 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 Chinese patent with publication number CN115864001A discloses a terahertz metamaterial based on a three-dimensional reconfigurable open resonant ring of vanadium dioxide, comprising: a high-resistance silicon wafer substrate, a three-dimensional open resonant ring formed on the substrate as a structural unit and extending in a two-dimensional array according to the radial and axial periods of the resonant ring; each structural unit has a vanadium dioxide film as a lower layer and a gold film as an upper layer, and a three-dimensional structure formed by curling a double-layer strip of vanadium dioxide and gold film; wherein the strip length is 100-150 μm and the width is 10-20 μm, and the three-dimensional structure formed by curling the double-layer strip is a three-dimensional open resonant ring; at room temperature, the central angle corresponding to the initial resonant ring opening is 300 degrees to 320 degrees; in the two-dimensional array, the row spacing is 5-10 μm and the column spacing is 10-30 μm; specific peak resonance absorption is achieved by the gold film, and the opening angle of the resonant ring is adjusted by the phase change of the vanadium dioxide film, thereby dynamically modulating the terahertz resonance wavelength.

[0008] A Chinese patent with publication number CN106785294A discloses a three-dimensional toroidal magnetic dipole device and a preparation method thereof. The device is formed by an array of multiple structural units, each of which includes: a self-supporting insulating dielectric film, used as a supporting base; a suspended portion, formed by cutting and folding the self-supporting insulating dielectric film, the number of which is an even number and not less than four, fixed to the same side of the self-supporting insulating dielectric film, and an angle is formed between the corresponding suspended portions and the self-supporting insulating dielectric film; and a metal open resonant ring, the number of which is equal to the number of the suspended portions, which is arranged one by one on the side surface of the suspended portion, used to bind the magnetic field and generate a magnetic dipole, the magnetic dipoles are connected end to end to form a closed loop, and the closed loop is used to achieve toroidal magnetic dipole resonance.

[0009] At present, a variety of three-dimensional metamaterial structures have been developed based on surface stress or using advanced technologies such as electron beam bombardment to fold and curl. Although these devices manufactured by fine processing technology have unique physical properties in theory, they face a common problem in practical applications: due to the intrinsic stress effect, these devices are very prone to collapse, resulting in poor structural stability. In addition, in the process of patterning these structures, highly toxic organic photoresists are usually required as masks for pattern processing transfer. This practice 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 operators. At the same time, the curling and folding process has poor controllability and low success rate, which makes it extremely difficult to mass-produce these complex three-dimensional structures. All these factors combined have greatly limited the practical application potential of such three-dimensional metamaterial structures in biosensing, microelectronics and other high-tech applications. Summary of the invention

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

[0011] A second object of the present invention 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 invention is to provide an application of a three-dimensional metamaterial structure, which has the advantages of working in the 7~10μm band, non-ionizing radiation and strong anti-interference ability, high sensitivity, and is suitable for the field of biosensing.

[0013] To achieve the above first object, the present invention provides the following technical solutions: A three-dimensional metamaterial structure comprises a metal reflective layer, a transmission medium layer, a metal connection layer, and a metal micron column group arranged in sequence from bottom to top, wherein the metal micron column group comprises a first metal micron column located at the center and a plurality of second metal micron columns arranged around the first metal micron column, and the metal connection layer connects the bottoms of the first metal micron column and the second metal micron column respectively.

[0014] Furthermore, the metal of the metal reflective layer is Au or Ag.

[0015] And / or, the medium of the transmission medium layer is SiO2 or Al2O3.

[0016] And / or, the metal of the metal connection layer is Au or Ag.

[0017] And / or, the metal of the metal micro-column group is Au or Ag.

[0018] Furthermore, the orthographic projections of the metal reflective layer, the transmissive medium layer, the first metal micro-column and the second metal micro-column in the vertical direction are independently circular or regular polygonal, the orthographic projection of the metal connecting layer in the vertical direction is radially radiating from the first metal micro-column to the plurality of second metal micro-columns respectively, and the edges of the metal reflective layer and the transmissive medium layer are approximately on the same edge line.

[0019] Furthermore, the orthographic projections of the metal reflective layer, the transmissive medium layer, the first metal micro-column and the second metal micro-column in the vertical direction are independently square.

[0020] Furthermore, the height of the metal reflective layer is h1=0.1~0.2μm, the height of the transmissive medium layer is h2=0.2~0.3μm, the height of the metal connecting layer is h3=0.1~0.2μm, and the height of the first metal micro-column and the second metal micro-column is h4=0.4~1.0μm.

[0021] Furthermore, the height of the metal reflective layer is h1=0.1 μm, the height of the transmissive medium layer is h2=0.2 μm, the height of the metal connection layer is h3=0.1 μm, and the height of the first metal micro-column and the second metal micro-column is h4=0.6 μm.

[0022] Furthermore, the radius or opposite side distance P of the metal reflective layer and the transmissive medium layer is 2.2-2.8 μm, the radiation 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 micro-column and the second metal micro-column is 0.1-0.3 μm.

[0023] Furthermore, the radius or opposite side distance P of the metal reflective layer and the transmissive medium layer is 2.4 μm, the opposite side distance L of the metal micro-column group is 2.3 μm, and the radius or opposite side distance w of the first metal micro-column and the second metal micro-column is 0.2 μm.

[0024] To achieve the above second purpose, the present invention provides the following technical solutions: A low-temperature electron beam processing method for a three-dimensional metamaterial structure comprises the following steps: S1 prepares a substrate, and first deposits a metal reflection layer and a transmission medium layer in sequence on the surface of the substrate to obtain a first sample; S2: firstly transferring the first sample into the mirror cavity of a field emission scanning electron microscope, and then depositing a first amorphous ice layer on the surface of the transmission medium layer under low temperature conditions, and then performing electron beam exposure to remove the first amorphous ice layer in the structure area, and then transferring the first sample into an electron beam coating cavity, and depositing a metal connection layer on the surface of the transmission medium layer to obtain a second sample; S3: firstly transferring the second sample into the mirror cavity of a field emission scanning electron microscope, and then depositing a second amorphous ice layer on the surface of the metal connection layer under low temperature conditions, and then performing electron beam exposure to remove the second amorphous ice layer in the structure area, and then transferring the second sample into an electron beam coating cavity, and depositing a metal micron column group on the surface of the transmission medium layer to obtain a third sample; S4: After the third sample is heated to room temperature, gas is purged to remove the first amorphous ice layer, the second amorphous ice layer and the metal film in the non-structured area to obtain a three-dimensional metamaterial structure.

[0025] Furthermore, in S1, the metal reflective layer is formed by deposition by one of electron beam evaporation, thermal evaporation and sputtering.

[0026] Furthermore, in the above S1, the method of depositing the transmission medium layer is one of electron beam evaporation, thermal evaporation and ion enhanced chemical vapor deposition (PECVD).

[0027] Furthermore, in S2 and S3, the low temperature condition is a temperature condition equal to or lower than the desublimation point of water vapor at a corresponding air pressure, and the first amorphous ice layer and the second amorphous ice layer are solid films formed by desublimation of water vapor.

[0028] Furthermore, in S2 and S3, the height of the first amorphous ice layer exceeds the total height of the metal connecting layer and the metal micron column group, and the height of the second amorphous ice layer exceeds the height of the metal micron column group.

[0029] Furthermore, in S2 and S3, the electron beam energy of the electron beam exposure is controlled to be 1-30 keV, and the electron area dose is controlled to be 0.1-5.0 C / cm 2 , the electron beam spot step size is 0.001~0.100μm.

[0030] Furthermore, in S2, the method of depositing the metal connection layer is one of electron beam evaporation, thermal evaporation and sputtering.

[0031] Furthermore, in S3, the deposition method for forming the metal micron column group is one of electron beam evaporation, thermal evaporation and sputtering.

[0032] To achieve the third objective, the present invention provides the following technical solutions: Application of a three-dimensional metamaterial structure in mid-infrared refractive index sensor.

[0033] In summary, the beneficial technical effects of the present invention are: The metal reflection layer, metal connection layer and metal micron column group of the three-dimensional metamaterial structure of the present invention are composed of the same metal material, wherein the metal reflection layer is used to reflect the incident light and enhance the detection signal, the transmission medium layer is used to avoid contact short circuit between the upper and lower structures, and at the same time, it must have a relatively high transmittance, and the metal connection layer and the metal micron column group are resonance units. Under the excitation of the incident light, the free electrons on the metal surface of the resonance unit will form a collective oscillation at the interface between the metal and the medium. When the oscillation frequency is the same as the evanescent wave frequency generated by total reflection at the interface, a resonant absorption effect, namely, surface plasmon resonance (SPR), will be generated, and then a resonant absorption trough (dip) will be 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 refractive index of the environment increases, the dip will move to a larger wavelength (red shift), thereby greatly increasing the contact area between the detection object and the sensor, and at the same time enhancing the dipole resonance effect, so that the performance indicators such as the detection sensitivity are significantly improved, especially the height of the metal micron column group has a great influence on the sensitivity; When the three-dimensional metamaterial structure of the present invention is actually used, the object to be detected can be coated or dripped on the surface of the sensor, or the sensor can be placed in a liquid environment to be tested, and the spectrum of the sensor can be tested by a Fourier infrared spectrometer (FTIR) or a similar type of spectrum analysis instrument. The test can be first performed with a variety of materials with known refractive indices to obtain the corresponding relationship between the wavelength and the refractive index at the dip, and then the object to be detected can be tested as standard data. Then, the refractive index of the object to be detected can be read from the standard data, and then the composition, concentration and other information of the object to be detected can be obtained by analysis. In scenarios such as the concentration detection of biological substances such as exosomes, the three-dimensional metamaterial structure can also effectively capture and fix micron-sized biological macromolecules or organelles to ensure the stability of the detection signal. The three-dimensional metamaterial structure of the present invention has good structural stability. The sensor is repeatedly cleaned several times for 5 minutes each time in a liquid environment such as pure water, ethanol and acetone at a temperature range of 20-80°C and a frequency of 40KHz using an ultrasonic cleaning machine. The three-dimensional metamaterial structure remains intact through atomic force microscopy (AFM), which proves its stability in working in a liquid environment or flow state. The method of the present invention utilizes two cycles of low-temperature electron beam exposure-electron beam evaporation process, and can realize the processing and stacking of multi-layer patterns with a set of equipment under the premise of single sample in and out, so as to form a three-dimensional metamaterial structure with tight interlayer connection and high structural strength. In addition, the process utilizes water vapor condensed into an amorphous ice layer as a mask for patterning processing, and does not introduce any toxic organic photoresist. All raw materials are non-toxic and harmless. In addition, the material and structure of the three-dimensional metamaterial structure are simple, and the minimum line width exceeds 200nm, which reduces the processing accuracy requirements. The method can also be used to control the height of the metal micron column group, and the sensing sensitivity can be increased from 1740nm / RIU to 3580~5800nm / RIU, which greatly improves the sensing sensitivity. The application of the three-dimensional metamaterial structure of the present invention in the mid-infrared band refractive index sensor works in the mid-infrared band. The mid-infrared light energy is relatively low and will not generate harmful ionizing radiation to biological samples. The specific working wavelength range is between 7 and 10 μm. It does not generate ionizing radiation that is harmful to the organism, and effectively avoids the main absorption peaks of water molecule hydrogen bonds in the infrared and terahertz bands, thereby avoiding the interference of irrelevant signals in the water-containing test 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 biosensing. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic diagram of the three-dimensional structure of the three-dimensional metamaterial structure of Example 1 of the present invention.

[0035] Figure 2 It is a schematic diagram of the main structure of the three-dimensional metamaterial structure of Example 1 of the present invention.

[0036] Figure 3 It is the reflection spectrum diagram of Example 1 of the present invention.

[0037] Figure 4 It is a flow chart of the method provided in Example 2 of the present invention.

[0038] Figure 5 This is an AFM image of the three-dimensional metamaterial structure of Example 2 of the present invention.

[0039] Figure 6 This is a sensor sensitivity detection diagram of Example 3 of the present invention.

[0040] In the figure, 1. metal reflective layer; 2. transmission medium layer; 3. metal connecting layer; 4. metal micron column group. DETAILED DESCRIPTION

[0041] In order to make the technical means, creative features, objectives and functions achieved by the present invention clearer and easier to understand, the present invention is further explained below in conjunction with the accompanying drawings and specific implementation methods.

[0042] Example 1: Reference Figure 1 , is a three-dimensional metamaterial structure disclosed in the present invention, comprising a metal reflective layer 1, a transmissive medium layer 2, a metal connection layer 3, and a metal micron column group 4 arranged in sequence from bottom to top. The metal micron column group 4 comprises a first metal micron column located in the center, and four second metal micron columns arranged around the first metal micron column, and the metal connection layer 3 connects the bottoms of the first metal micron column and the second metal micron column respectively. The orthographic projections of the metal reflective layer 1, the transmissive medium layer 2, the first metal micron column and the second metal micron column in the vertical direction are independently square, and the orthographic projection of the metal connection layer 3 in the vertical direction is a cross-radial shape radiating from the first metal micron column to the four second metal micron columns respectively, and the edges of the metal reflective layer 1 and the transmissive medium layer 2 are approximately on the same edge line.

[0043] Reference Figure 2 To obtain the best sensor performance, the metal of the metal reflective layer 1, the metal connection layer 3 and the metal micro-column group 4 is Au, and the medium of the transmissive medium layer 2 is SiO2. At the same time, the height of the metal reflective layer 1 is h1 = 0.1μm, the height of the transmissive medium layer 2 is h2 = 0.2μm, the height of the metal connection layer 3 is h3 = 0.1μm, and the height of the first metal micro-column and the second metal micro-column is h4 = 0.6μm. The distance P between the opposite sides of the metal reflective layer 1 and the transmissive medium layer 2 is x =P y =2.4μm, the radiation diameter of the metal connection layer 3 is L1=L2=2.3μm, and the distance between the opposite sides of the first metal micro-column and the second metal micro-column is w1=w2=0.2μm.

[0044] from Figure 3 It can be seen that by reading the environment refractive index n and the wavelength value when the absorption rate is the highest, it can be obtained that the refractive index sensitivity of the three-dimensional metamaterial structure of this embodiment is 3580nm / RIU.

[0045] Example 2: Reference Figure 4 , which is a low-temperature electron beam processing method for a three-dimensional metamaterial structure disclosed in the present invention, is different from Example 1 in that it includes the following steps: S1 prepares a substrate (usually single crystal Si), and first deposits a metal reflection layer 1 and a transmission medium layer 2 on the surface of the substrate in sequence to obtain a first sample; The metal reflective layer 1 is formed by electron beam evaporation at a deposition rate of 0.040 nm / s.

[0046] The transmission medium layer 2 is formed by electron beam evaporation at a deposition rate of 0.025 nm / s.

[0047] S2: firstly transfer the first sample into the mirror cavity of the field emission scanning electron microscope, and then deposit a first amorphous ice layer on the surface of the transmission medium layer 2 under low temperature conditions, and then perform electron beam exposure to remove the first amorphous ice layer in the structure area, and then transfer the first sample into the electron beam coating cavity, and deposit a metal connection layer 3 on the surface of the transmission medium layer 2 to obtain a second sample; Low temperature conditions are temperature conditions equal to or lower than the condensation point of water vapor at the corresponding gas pressure; The first amorphous ice layer is a solid film formed by condensation of water vapor, and the height of the first amorphous ice layer exceeds the total height of the metal connection layer 3 and the metal micron column group 4; The electron beam energy of the electron beam exposure is 5 keV, and the electron area dose is 0.5 C / cm 2 , the electron beam spot step size is 0.008μm.

[0048] The metal connection layer 3 is formed by electron beam evaporation at a deposition rate of 0.040 nm / s.

[0049] S3 first transfers the second sample into the mirror cavity of the field emission scanning electron microscope, and then deposits a second amorphous ice layer on the surface of the metal connection layer 3 under low temperature conditions, and then performs electron beam exposure to remove the second amorphous ice layer in the structure area, and then transfers the second sample into the electron beam coating cavity, and deposits a metal micron column group 4 on the surface of the transmission medium layer 2 to obtain a third sample; Low temperature conditions are temperature conditions equal to or lower than the condensation point of water vapor at the corresponding gas pressure; The second amorphous ice layer is a solid film formed by condensation of water vapor, and the height of the second amorphous ice layer exceeds the height of the metal micron column group 4; The electron beam energy of the electron beam exposure is 5 keV, and the electron area dose is 0.9 C / cm 2 , the electron beam spot step size is 0.008μm.

[0050] The metal micron column group 4 is deposited by electron beam evaporation, and the deposition rate is 0.040 nm / s.

[0051] S4 heats the third sample to room temperature and then purges it with nitrogen or compressed air to remove the first amorphous ice layer, the second amorphous ice layer and the metal film in the non-structured area to obtain a three-dimensional metamaterial structure.

[0052] from Figure 5 It can be seen that the three-dimensional metamaterial structure prepared in this embodiment has good structural stability. Specifically, the sensor was repeatedly cleaned several times for 5 minutes each time using an ultrasonic cleaning machine in a liquid environment such as pure water, ethanol and acetone, at a temperature range of 20-80°C and a frequency of 40KHz. The atomic force microscope (AFM) showed that the three-dimensional metamaterial structure remained intact, proving its stability in a liquid environment or flow state.

[0053] Example 3: Application of a three-dimensional metamaterial structure disclosed in the present invention in a mid-infrared band refractive index sensor. The difference from Example 1 is that the height h4 of the first metal micro-column and the second metal micro-column is 0~1.0μm.

[0054] from Figure 6 It can be seen that the height of the metal micron column group 4 has a great influence on the sensitivity. When h4=0μm, the three-dimensional metamaterial structure is equivalent to a two-dimensional planar structure, and the sensitivity is only about 1740nm / RIU. When h4 is increased to 0.6μm as shown in Example 1, the sensitivity is 3580nm / RIU; when h4 is increased to 1μm, the sensitivity can rise to 5800nm / RIU. The above proves the improvement effect of the three-dimensional metamaterial structure on the sensor performance.

[0055] In addition, the sensor shown in this embodiment works in the mid-infrared band, the mid-infrared light energy is low, and will not produce harmful ionizing radiation to biological samples. The specific working wavelength range is between 7 and 10 μm, which effectively avoids the main absorption peak of water molecule hydrogen bonds in the infrared and terahertz bands, thereby avoiding the interference of irrelevant signals in the water-containing test 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 biosensing.

[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A three-dimensional metamaterial structure, characterized in that: The invention comprises a metal reflective layer (1), a transmission medium layer (2), a metal connection layer (3), and a metal micron column group (4) which are arranged in sequence from bottom to top. The metal micron column group (4) comprises a first metal micron column located at the center and a plurality of second metal micron columns arranged around the first metal micron column. The metal connection layer (3) respectively connects the bottoms of the first metal micron column and the second metal micron column.

2. A 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 micro-column group (4) are Au or Ag, and the medium of the transmission medium layer (2) is SiO2 or Al2O3.

3. A three-dimensional metamaterial structure according to claim 2, characterized in that: The orthographic projections of the metal reflective layer (1), the transmissive medium layer (2), the first metal micron column and the second metal micron column in the vertical direction are independently circular or regular polygonal, the orthographic projection of the metal connection layer (3) in the vertical direction is radially radiating from the first metal micron column to the plurality of second metal micron columns, and the edges of the metal reflective layer (1) and the transmissive medium layer (2) are approximately on the same edge line.

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

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

6. A low-temperature electron beam processing method for a three-dimensional metamaterial structure according to any one of claims 1 to 5, characterized in that: The following steps are included: S1: preparing a substrate, first depositing a metal reflection layer (1) and a transmission medium layer (2) on the surface of the substrate in sequence, to obtain a first sample; S2: firstly transferring the first sample into the mirror cavity of a field emission scanning electron microscope, and then depositing a first amorphous ice layer on the surface of the transmission medium layer (2) under low temperature conditions, and then performing electron beam exposure to remove the first amorphous ice layer in the structure area, and then transferring the first sample into an electron beam coating cavity, and depositing a metal connection layer (3) on the surface of the transmission medium layer (2) to obtain a second sample; S3: firstly transferring the second sample into the mirror cavity of a field emission scanning electron microscope, and then depositing a second amorphous ice layer on the surface of the metal connection layer (3) under low temperature conditions, and then performing electron beam exposure to remove the second amorphous ice layer in the structure area, and then transferring the second sample into the electron beam coating cavity, and depositing a metal micron column group (4) on the surface of the transmission medium layer (2) to obtain a third sample; S4: After the third sample is heated to room temperature, gas is purged to remove the first amorphous ice layer, the second amorphous ice layer and the metal film in the non-structured area to obtain a three-dimensional metamaterial structure.

7. The low-temperature electron beam processing method for 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 desublimation point of water vapor at a corresponding air pressure, and the first amorphous ice layer and the second amorphous ice layer are solid films formed by desublimation of water vapor.

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

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

Images