Diamond metasurface preparation method based on silicon nano array

Abstract

The invention discloses a preparation method of a diamond metasurface based on a silicon nano array, which comprises the following steps of: firstly, etching an inwards concave nano array on the surface of a silicon wafer, then putting the silicon wafer with the nano array into a diamond nano particle suspension for ultrasonic crystal planting, and then growing diamond on the surface of the silicon wafer after crystal planting, so as to obtain the diamond metasurface. And finally, removing the silicon wafer with the nano array to obtain the diamond with the surface nano structure. According to the method provided by the invention, the nano-column structure is prepared by directly etching the monocrystalline silicon, and then the diamond is grown on the silicon, so that the condition that the metasurface is obtained by directly etching and preparing the nano-column structure on the surface of the diamond is avoided, and in the actual production process, the cost of the monocrystalline silicon is relatively low; the process for preparing the nano-column structure by directly etching the monocrystalline silicon and growing the diamond on the chip is mature, the operation difficulty is low, the cost and difficulty for finally obtaining the diamond metasurface are greatly reduced, and large-scale preparation and follow-up device research of the diamond metasurface are facilitated.

Description

Technical Field

[0001] The invention relates to a method for preparing a diamond super surface based on a silicon nano array, and belongs to the technical field of super surface optics. Background Art

[0002] Metasurface technology refers to ultra-thin artificial structures that can control light and electromagnetic waves. Metasurface structures can flexibly control the polarization, phase, polarization mode, and propagation mode of electromagnetic waves, and are often used in the processing of integrated circuits, optical lenses, and communication equipment.

[0003] Diamond supersurfaces can be divided into single-crystal diamond supersurfaces and polycrystalline diamond supersurfaces at this stage. Single-crystal diamond has good quality, better optical and electrical properties, and good performance consistency at the nanometer level. Single-crystal diamond is obtained by deposition, and the growth and processing process is complicated, and large-sized single-crystal diamond is difficult to obtain; polycrystalline diamond has low production cost, simple preparation, can obtain large-sized diamond, and has stable electrical and optical properties. The preparation of the two types of diamond supersurfaces is usually carried out by etching the diamond surface to obtain a nano-pillar structure, but due to the directionality of the etching, the etching rate, and the poor etching quality, the production of the diamond supersurface obtained by etching is difficult, and the cost is high, making it difficult to achieve low-cost mass production. Summary of the invention

[0004] The invention discloses a method for preparing a diamond super surface based on a silicon nanoarray.

[0005] The technical solution adopted by the present invention is:

[0006] A method for preparing a diamond super surface based on silicon nanoarrays, which includes first etching an inwardly concave nanoarray on the surface of a silicon wafer, then placing the silicon wafer with the nanoarray in a diamond nanoparticle suspension for ultrasonic crystal planting, then growing diamond on the surface of the silicon wafer after the crystal planting, and finally removing the silicon wafer with the nanoarray to obtain a diamond with a surface nanostructure.

[0007] Preferably, the nanoarray is a cylindrical, square, elliptical or triangular nanoarray.

[0008] Preferably, the height H of the cylindrical nanoarray is between 100 nm and 200 nm.

[0009] Preferably, the diameter D of the cylindrical nanoarray is between 150 nm and 250 nm.

[0010] Preferably, the gap L of the cylindrical nanoarray is between 80 nm and 200 nm.

[0011] Preferably, the particle size of the diamond nanoparticles in the diamond nanoparticle suspension is 3-5 nm, and the final nucleation surface density is controlled to be 10 7 -10 8 cm ―2 .

[0012] Preferably, the silicon wafer is an N-type silicon wafer, and etching and subsequent diamond growth are performed on a surface with a crystal orientation of (100).

[0013] Preferably, diamond is grown using MPCVD, with a growth temperature between 950° C. and 1050° C., a microwave power between 3800 W and 4200 W, and a methane concentration between 2% and 4%.

[0014] Preferably, mechanical polishing and wet etching are used to remove the silicon wafer with the nanoarray. To improve efficiency and avoid damaging the diamond, mechanical polishing is usually performed until the thickness of the residual silicon wafer is within 30 μm, and then wet etching is performed to remove the residual silicon wafer and the nanoarray thereon.

[0015] The beneficial effects of the present invention are:

[0016] (1) Breakthrough in diamond surface etching to obtain nano-pillar structure. Due to the directionality, etching rate and poor etching quality of the etching, the production of diamond super-surface obtained by etching is difficult and the cost is high, which makes it difficult to achieve low-cost mass production. The diamond surface nanostructure array can be prepared at low cost and difficulty to obtain the diamond super-surface.

[0017] (2) Precisely patterned and regularly shaped nanostructure arrays are achieved on silicon wafers. Microstructures suitable for diamond growth are prepared on silicon wafers through ultrasonic crystal planting. After MPCVD growth, the substrate is wet removed to achieve precise and regular nanostructure array preparation on the diamond surface and obtain a diamond super surface.

[0018] (3) Different array periods or different sizes of cylindrical structures have different effects on the optical properties of the diamond metasurface. Researchers can prepare different cylindrical structures as needed to meet the preparation of diamond metasurface devices for different application scenarios.

[0019] (4) Compatible with traditional semiconductor processes, it facilitates the subsequent optimization, integration, and deviceization of diamond metasurfaces.

[0020] (5) Compared with the supersurface formed by direct etching of diamond, the diamond supersurface obtained by imprinting after the preparation of silicon micro-nanostructures with mature preparation technology can be customized to prepare diamond micro-nanostructures, which has more significant advantages in terms of size accuracy and morphology customization. The precise control of size avoids the size effect and edge effect generated in the device preparation, and reduces and avoids electrical breakdown and leakage, thus obtaining devices with better performance. The precise control of graphic morphology can provide the prerequisite for the preparation of devices of more sizes and the realization of devices with different performances. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a cross-sectional schematic diagram of Example 1 based on the silicon nanostructured diamond supersurface.

[0022] Figure 2 This is a schematic top view of the silicon nanostructured diamond supersurface according to Example 1.

[0023] Figure 3 Schematic diagram of the preparation process of silicon nanostructured diamond supersurface in Example 1.

[0024] Figure 4 This is a cross-sectional schematic diagram of the preparation process of Example 1 based on silicon nanostructured diamond supersurface.

[0025] Figure 5 Schematic diagram of the device for preparing diamond based on the MPCVD method of silicon nanostructured diamond supersurface in Example 1.

[0026] Figure 6 This is a scanning electron microscope photograph of a silicon nanostructured diamond supersurface prepared in Example 1.

[0027] Description of the markings in the figure:

[0028] 1-silicon substrate; 2-PMMA glue; 3-silicon dioxide; 4-diamond; 5-sample; 6-sample stage; 7-deposition chamber; 8-plasma; 9-transparent observation mirror on the top of the chamber. DETAILED DESCRIPTION

[0029] The present invention is further described below in conjunction with embodiments, but the description of the embodiments does not impose any limitation on the protection scope of the present invention.

[0030] Unless otherwise defined, all technical terms and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the present invention, and the terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. In addition, although demonstrations of parameters containing specific values ​​may be provided herein, it should be understood that the parameters do not need to be exactly equal to the corresponding values, but can be approximated to the corresponding values ​​within an acceptable error tolerance or design constraint. The directional terms mentioned in the embodiments, such as "up", "down", "front", "back", "left", "right", etc., are only directions with reference to the accompanying drawings. Therefore, the directional terms used are used to illustrate rather than to limit the scope of protection of the present invention.

[0031] Unless otherwise specified, the materials and instruments used in the following examples can be obtained from conventional commercial channels.

[0032] Example 1

[0033] like Figure 1 , 3 As shown in 4-5, the present invention proposes a method for preparing a diamond super surface based on silicon nanopillars, comprising the following steps:

[0034] Step S1: taking a single-sided N-type polished silicon wafer 1 with a crystal orientation of (100) and a diameter of 50.8 mm as a substrate, and sequentially using an acetone solution with a content of 99.5% for ultrasonic cleaning for 10 minutes, an anhydrous ethanol solution with a content of 99.7% for ultrasonic cleaning for 10 minutes, and a deionized water solution for ultrasonic cleaning for 10 minutes, wherein the acetone and ethanol cleaning are both for removing organic matter and other impurities on the surface of the N-type single-sided polished silicon wafer 1, and the deionized water is for removing residual acetone and ethanol solution, and the cleaning sequence cannot be adjusted to avoid affecting the cleanliness of the N-type single-sided polished silicon wafer (1);

[0035] Step S2: On the N-type silicon substrate, spin-coat a 150 nm thick PMMA glue 2. The PMMA glue is selected because it has low viscosity and the amount of glue remaining at the edge of the sample after coating is minimal, which is conducive to making a sample as large as possible;

[0036] Step S3: Electron beam exposure, electron beam voltage 100Kv, current 200pA, electron dose 1000μC / cm 2 , a circular hole array was exposed on PMMA glue 2, the diameter of the circular hole was about 200nm, the gap was 100nm, the exposure time was 3s, and it was baked at 120℃ for 2min after exposure, placed in alkaline developer and allowed to stand for 40s, and then transferred to deionized water to remove the residual developer on the surface;

[0037] Step S4: Deposit silicon dioxide 3 on the PMMA glue 2 by plasma enhanced chemical vapor deposition (PECVD) and introduce SiN 4 and O 2 , gas flow rate is 10sccm / s, deposition temperature is 250℃, deposition time is 2min, deposition thickness is 300nm;

[0038] Step S5: using a wet degumming method, placing the deposited silicon wafer 1 in a water bath at 80° C., soaking it in N-methylpyrrolidone for 25 minutes, and removing the silicon dioxide 3 outside the pattern area;

[0039] Step S6: The processed silicon wafer 1 is ultrasonically cleaned in 99.5% acetone solution for 10 min, ultrasonically cleaned in 99.7% anhydrous ethanol solution for 10 min, and ultrasonically cleaned in deionized water solution for 10 min, and dried with N2;

[0040] Step S7: using an inductively coupled plasma (ICP) etching method to etch the silicon wafer 1 with the silicon dioxide 3 as a mask to form a silicon cylindrical nanoarray, the ICP power is set to 300 W, the gas introduced is 28 sccm argon and 80 sccm hydrogen bromide, the working pressure is 800 Pa, and the etching time is 45 s;

[0041] Step S8: removing the silicon dioxide 3 of the mask by wet method, placing the etched silicon wafer 1 in a BOE solution and soaking it for 6 minutes, then taking it out to remove the silicon dioxide 3 used as a mask;

[0042] Step S9: The processed silicon wafer 1 is ultrasonically cleaned in 99.5% acetone solution for 10 min, ultrasonically cleaned in 99.7% anhydrous ethanol solution for 10 min, and ultrasonically cleaned in deionized water solution for 10 min, and blown dry with N2;

[0043] Step S10: placing the cleaned silicon wafer 1 into a diamond nanoparticle suspension for ultrasonic crystal planting, so that a separated microstructure suitable for the growth of diamond single crystals is formed on the single-side polished silicon wafer 1, wherein the diameter of the diamond particles in the diamond nanoparticle suspension is 4nm, and the ultrasonic crystal planting is performed for 20 minutes, and the surface density of the microstructure surface is controlled by controlling the concentration, oscillation intensity and oscillation time of the diamond nanoparticle suspension;

[0044] The ultrasonic crystal planting causes the particles in the suspension of diamond nanoparticles to form scratches on the surface of the silicon wafer 1 and to deposit in the gaps of the nanostructures through vibration;

[0045] The mass concentration of the diamond nanoparticle suspension is 2.5 kg / L, and the characteristic size of the diamond particles is 4 ± 0.8 nm;

[0046] Step S11: The silicon wafer 1 after the crystal planting is ultrasonically cleaned in 99.5% acetone solution for 10 minutes, in 99.7% anhydrous ethanol solution for 10 minutes, and in deionized water solution for 10 minutes, to remove the diamond nanoparticle suspension remaining on the surface of the silicon wafer 1;

[0047] Step S12: placing the cleaned silicon wafer 1 on a sample stage 6 in a deposition chamber 7 of a microwave plasma chemical vapor deposition device (MPCVD), growing diamond single crystal particles at the microstructure of the silicon wafer 1, and the grown diamond particles forming a diamond substrate, and continuing to grow to form a single crystal diamond 4 with a smooth surface;

[0048] The detailed process and parameters of diamond growth are as follows: vacuum is firstly evacuated to 10 ―5 Torr; after the vacuum is completed, the plasma is generated by starting 8, and the transparent observation mirror 9 on the top of the cavity is used to observe whether the plasma is directly above the sample 5, and then the conditions in the cavity are adjusted to the growth state. The growth conditions are as follows: the growth temperature is 1000-1050°C, the microwave power is 4000W, the flow rates of hydrogen and methane are 600sccm and 12sccm respectively (i.e., the methane concentration is 2%), and the pressure in the cavity is 300Torr. This series of growth conditions is maintained for 4 hours.

[0049] Step S13: Use mechanical polishing and wet etching methods to remove the silicon wafer substrate 1 and the silicon cylinder array thereon, mechanically polish the grown diamond to a certain thickness and then put it into an etching mixture (HNO3, HF and water), and after etching, complete the preparation of the diamond surface nanostructure to obtain a diamond super surface 4.

[0050] Figure 2 is a schematic top view of the diamond supersurface 4 prepared in Example 1, Figure 6 is an electron microscope photograph of the diamond supersurface 4 prepared in Example 1. Figure 2 and 6 It can be seen that the diamond supersurface 4 is a polycrystalline diamond with a subwavelength nanocolumn structure, including a single crystal diamond and a diamond nanocolumn array grown thereon, wherein the diamond nanocolumn array is complementary to the silicon cylindrical nanoarray etched on the silicon wafer 1, so the nanocolumn structure on the diamond surface depends on the nanocolumn structure on the base silicon wafer 1, and the diamond growth time is adjusted according to the height and diameter of the nanocolumns on the base silicon wafer 1. The diamond supersurface 4 can reduce the absorption of near-infrared light and visible light by the polycrystalline diamond supersurface.

[0051] In this embodiment, circular cylindrical periodic nanoarrays are used. Different array periods or cylindrical structures of different sizes have different effects on the optical properties of the diamond metasurface. Researchers can prepare different cylindrical structures as needed to meet the needs of preparing diamond metasurface devices for different application scenarios. Nanoarrays of other shapes can also be prepared as needed, such as square columns, elliptical columns, triangular columns, etc.

[0052] In summary, the present invention provides a method for preparing a diamond supersurface based on a silicon nanopillar structure, which prepares a nanopillar structure by directly etching single-crystal silicon, and then grows diamond on silicon, thereby avoiding directly etching the diamond surface to prepare the nanopillar structure to obtain a supersurface. In the actual production process, due to the low cost of single-crystal silicon, the process of directly etching single-crystal silicon to prepare a nanopillar structure and growing diamond on-chip is mature and has low operational difficulty, and the cost and difficulty of finally obtaining a diamond supersurface are greatly reduced, which is conducive to the large-scale preparation of diamond supersurfaces and subsequent device research.

[0053] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for preparing a diamond supersurface based on a silicon nanoarray, characterized in that First, an inward-concave nanoarray is etched on the surface of a silicon wafer. Then the silicon wafer with the nanoarray is placed in a diamond nanoparticle suspension for ultrasonic crystal planting. Diamond is then grown on the surface of the silicon wafer after seeding. Finally, the silicon wafer with the nanoarray is removed to obtain diamond with a surface nanostructure.

2. The method for preparing a diamond supersurface according to claim 1, wherein: The nanoarray is a cylindrical, square, elliptical or triangular nanoarray.

3. The method for preparing a diamond supersurface according to claim 2, characterized in that: The height H of the cylindrical nanoarray is between 100 nm and 200 nm.

4. The method for preparing a diamond supersurface according to claim 3, characterized in that: The diameter D of the cylindrical nanoarray is between 150 nm and 250 nm.

5. The method for preparing a diamond super surface according to claim 4, characterized in that: The gap L of the cylindrical nanoarray is between 80 nm and 200 nm.

6. The method for preparing a diamond supersurface according to claim 1, characterized in that: The particle size of the diamond nanoparticles in the diamond nanoparticle suspension is 3-5 nm, and the final nucleation surface density is controlled to be 10 7 -10 8 cm ―2 .

7. The method for preparing a diamond supersurface according to any one of claims 1 to 6, characterized in that: The silicon wafer is an N-type silicon wafer, and etching and subsequent diamond growth are performed on the surface with a crystal orientation of (100).

8. The method for preparing a diamond super surface according to claim 7, characterized in that: Diamond is grown using MPCVD, with a growth temperature between 950°C and 1050°C, a microwave power between 3800W and 4200W, and a methane concentration between 2% and 4%.

9. The method for preparing a diamond supersurface according to claim 7, characterized in that: Mechanical polishing and wet etching methods are used to remove the silicon wafer with the nanoarray.

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