A preparation method for a single-layer disc 3D structure supported by a nano-tip

Abstract

The present invention belongs to the field of micro-nano structures and relates to a preparation method of a single-layer disc 3D structure supported by nano-tips. This method obtains a single-layer disc 3D structure supported by nano-tips through an electron beam thermal evaporation system, self-assembly technology, and reactive ion etching. Not only is the preparation process simple, low-cost, and highly repeatable, but also the structure has good stability and high tolerance. Compared with the metasurface supported by a silicon substrate, the tip support greatly improves the transient signal oscillation modulation ability of the metasurface, significantly improves the optomechanical conversion efficiency and oscillation quality, and the quality factor is improved by several orders of magnitude compared with the ordinary silicon substrate.

Description

Technical Field

[0001] The present invention belongs to the field of micro-nano structures and relates to a preparation method of a single-layer disc 3D structure supported by a nano-tip. Background Art

[0002] Nano-opto-mechanical Systems (NOMs) is a multidisciplinary field that combines optical and mechanical properties, and its importance has become increasingly prominent with the development of micro-nano processing technologies. In particular, the acoustic vibration phenomenon in the gigahertz (GHz) frequency range plays an irreplaceable role in fields such as all-optical manipulation, quantum control, on-chip data processing, and optical sensing. Due to its advantages such as high intrinsic oscillation frequency, easy integration, and light weight, nano-opto-mechanical systems have shown great application potential in various cutting-edge technologies in recent years. With the progress of micro-nano processing technologies, the quality and performance of nano-opto-mechanical devices have been significantly improved. These systems can achieve the coupling between light and mechanical vibration at an extremely small scale, enabling optical signals to be processed with extremely high precision. Especially in the field of ultrasensitive mechanical sensing, nano-opto-mechanical systems can achieve higher sensitivity than traditional sensors through their high-frequency acoustic vibration response, and can effectively detect small changes in physical quantities. In terms of quantum control, nano-opto-mechanical systems provide a new platform for quantum information processing, quantum communication, and quantum sensing. Due to their extremely high precision and response speed in light manipulation, they can support the manipulation and measurement of quantum states.

[0003] Although some breakthroughs have been made in metastructure nano-optomechanical systems (MNOMSs) both theoretically and experimentally, and they have higher integration and performance, they still face many challenges in practical applications. One of the main problems is that the acoustic vibration of MNOMSs is affected by multiple energy loss channels, which leads to a decrease in the oscillation quality. Under high-frequency acoustic vibration, the energy loss of the system will significantly affect its stability and working efficiency, and may even cause the vibration to decay too quickly, thus limiting its application in high-precision optical signal processing. In addition, under the condition of high-energy pulsed laser pumping, non-radiative loss may occur in the metasurface of MNOMSs, which will cause damage to the structure and a decrease in transient optical performance, thereby affecting the reliability and durability of the system. Summary of the Invention

[0004] In view of the problems such as low oscillation quality of MNOMSs, the present invention proposes a preparation method of a single-layer disk 3D structure supported by nano-tips. The method aims to improve the optomechanical conversion efficiency and the oscillation quality of the optomechanical metasurface by designing a nano-opto-mechanical metasurface supported by nano-tips (TSNOMS), closing the main loss channels of photoacoustic vibration and finding a mild optomechanical excitation mode. At the same time, a preparation process with simple steps, large operation space, short preparation cycle and low cost is provided. The single-layer disk 3D structure supported by nano-tips prepared by this method has the characteristics of large-area controllable construction, good uniformity, high order and strong repeatability.

[0005] To achieve the above object, the present invention adopts the following scheme: A preparation method of a single-layer disk 3D structure supported by nano-tips, comprising the following steps:

[0006] S1 Deposit a layer of Au film on a silicon wafer;

[0007] S2 Self-assemble periodically arranged polymer microspheres on the surface of the Au film;

[0008] S3 Use reactive ion etching to reduce the volume of the microspheres with O2;

[0009] S4 Use reactive ion etching to physically bombard the Au not covered by the microsphere mask with Ar to expose the silicon wafer;

[0010] S5 Remove the microspheres;

[0011] S6 Use reactive ion etching to etch the exposed Si layer on the silicon wafer with SF6 to obtain a single-layer disk 3D structure supported by nano-tips.

[0012] Preferably, in S1, an Au film with a thickness of 30 nm is deposited using an electron beam thermal evaporation system, the deposition rate is 0.4 Å / s, the vacuum degree is 5×10 -4 Pa, and the voltage is 6 KV.

[0013] Preferably, in S2, the microspheres are specifically polystyrene microspheres.

[0014] Preferably, the etching in S3 specifically includes: horizontally placing the sample in the reactive ion etching chamber, with an etching power of 125 W, a pressure of 20 Pa, an O2 gas flow rate of 50 sccm, and an etching time of 25 s.

[0015] Preferably, S4 specifically includes: horizontally placing the silicon wafer processed through S1-S2 in the reactive ion etching chamber, with an etching power of 150 W, a pressure of 20 Pa, an Ar gas flow rate of 50 sccm, and an etching time of 90 s.

[0016] Preferably, in S5, a polyimide tape is used to physically exfoliate the polystyrene microspheres.

[0017] Preferably, S6 specifically includes: horizontally placing the sample in the reaction ion etching chamber, with an etching power of 125 W, a pressure of 20 Pa, an SF6 gas flow rate of 65 sccm, and an etching time of 70 - 90 s.

[0018] Preferably, the single - layer disk 3D structure supported by the nano - tips is used as a nano - optomechanical metasurface.

[0019] Preferably, in step S1, the silicon wafer needs to be cleaned, which specifically includes the following steps: using ultrapure water: hydrogen peroxide: ammonia water in a ratio of 6:2:1 for high - temperature heating treatment. The conductivity of the ultrapure water is 18.25 MΩ / cm, the concentration of hydrogen peroxide is 30%, the ammonia water is analytical pure AR, and the heating temperature is 270 °C until there are no obvious large air bubbles in the solution. Then cool down and take out the silicon wafer, and seal it in ultrapure water for storage at room temperature.

[0020] Compared with the metasurface supported by a silicon substrate, the tip - support in the present invention greatly improves the transient signal oscillation modulation ability of the metasurface, significantly improves the optomechanical conversion efficiency and oscillation quality, and the quality factor is improved by several orders of magnitude compared with the ordinary silicon - substrate nano - disk array. Description of the Drawings

[0021] Figure 1 It is a schematic diagram of the process for preparing the single - layer disk 3D structure supported by nano - tips.

[0022] Figure 2 It is a 3D schematic diagram of the single - layer disk 3D structure supported by nano - tips.

[0023] Figure 3 It is a top - view SEM image of the polystyrene microspheres etched for 25 s and the Si substrate etched for 70 s.

[0024] Figure 4 It is a cross - sectional SEM image of the polystyrene microspheres etched for 25 s and the Si substrate etched for 70 s.

[0025] Figure 5 It is a cross - sectional SEM image of the polystyrene microspheres etched for 25 s and the Si substrate etched for 80 s.

[0026] Figure 6 It is a cross - sectional SEM image of the polystyrene microspheres etched for 25 s and the Si substrate etched for 90 s.

[0027] Figure 7 It is a reflection spectrum diagram of the prepared structure.

[0028] Figure 8 It is a transient absorption spectrum diagram of the prepared structure. Detailed Implementation Modes

[0029] To further understand the present application, the following describes in detail the preparation method of the single-layer disc 3D structure supported by a nano-tip in combination with embodiments. The protection scope of the present application is not limited by the following embodiments. Embodiment

[0030] Deposit a 30-nm Au film on a cleaned silicon wafer through an electron beam thermal evaporation system, and then transfer 500-nm polystyrene microspheres onto the surface of the Au film by self-assembly technology to ensure large-area uniform arrangement of the polystyrene microspheres. Then, through reactive ion etching, first introduce O2 to reduce the volume of the polystyrene microspheres, with a flow rate of 50 sccm, a working pressure of 20 Pa, a power of 125 w, and an etching time of 25 s. Then introduce Ar to physically bombard the Au area not masked by the polystyrene microspheres, with a flow rate of 50 sccm, a working pressure of 20 Pa, a power of 150 w, and an etching time of 90 s. Then physically remove the polystyrene microspheres, and finally, through reactive ion etching, introduce SF6 to etch the Si substrate, with a flow rate of 65 sccm, a working pressure of 20 Pa, a power of 125 w, and an etching time of 70 s, as Figure 3 、 Figure 4 shown.

[0031] Adopting a semi-suspended state design opens the optical input energy channel and closes the mechanical and thermal output loss channels at the same time. On the one hand, compared with the metasurface supported by a silicon substrate, TSNOMS can more easily couple pulsed laser energy into the optomechanical system to excite photoacoustic vibrations, and its optical resonance absorption makes the periodic modulation of the transient signal by the metasurface easier to observe; on the other hand, the extremely small contact area between the substrate and the metal nanodisc array greatly reduces the heat loss of the metasurface. Under the same pumping conditions, the thermal strain of the tip-supported metasurface is more significant, and it can also close the energy channel of phonon leakage to the substrate to the greatest extent, reducing the energy loss from the substrate to close to the theoretical limit, thereby improving the optomechanical conversion efficiency and oscillation quality, avoiding the adverse effects caused by excessive energy loss and concentration, and reflecting the characteristics of gentle excitation.

[0032] Using a pulsed laser as the pump source, when it interacts with the gold metasurface, a large number of low-level electrons are excited to high levels. These non-thermal equilibrium high-level electrons transfer energy to the lattice, resulting in rapid thermal expansion of the structure and excitation of coherent acoustic vibration modes. This excitation method is based on non-local interband transitions, making the electron and lattice temperature distributions on the metasurface not highly localized, avoiding structural damage and transient optical performance degradation caused by non-radiative losses, and realizing gentle optomechanical excitation. Embodiment

[0033] The difference from Embodiment 1 is that the etching time of the Si substrate in the end is 80 s, asFigure 5 as shown Example

[0034] The difference from Example 1 is that the etching time of the Si substrate at the end is 90 s, as Figure 6 shown

[0035] By using a spectrometer, the reflection spectra of the Si substrate at different etching times were obtained, as Figure 7 shown. When the etching times are 70 s and 80 s, there is only one absorption peak at 700 nm. When the etching time is 90 s, a new absorption peak appears near 825 nm. The appearance of multiple modes may mean the coupling of multiple mechanical vibration modes or optical modes in the structure. This coupling can lead to the enhancement of nonlinear effects, such as nonlinear frequency conversion, mixing effects, etc. The appearance of multiple modes can also provide more degrees of freedom for the design of metamaterials. By regulating the resonance characteristics of multiple modes, more complex optical responses and functions can be achieved.

[0036] Using the pump-probe technique, we obtained the transient absorption spectrum of the single-layer disk 3D structure supported by a nanoscale tip, as Figure 8 shown. It can be seen that the prepared structure has a good oscillation quality, and the relaxation time reaches 4000 ps.

[0037] Femtosecond Pump-Probe Spectroscopy (FPPS) is a technique used to study the dynamics of materials and molecules. It uses an extremely short pulsed laser source for time-resolved spectroscopic analysis. Its basic principle can be divided into the following steps:

[0038] 1. Pump Pulse

[0039] The pump pulse is a very short laser pulse, usually at the femtosecond level (1 fs = 10 -15 s), used to excite molecules or substances in the sample. This laser pulse provides energy, causing changes in the electrons, vibrations, or other states in the sample, such as transitions from the ground state to the excited state.

[0040] 2. Probe Pulse

[0041] The probe pulse is also a femtosecond laser pulse, usually emitted at a certain time delay (called the delay time, usually in the picosecond to femtosecond range) after the pump pulse excites the sample, used to detect the physical or chemical processes evolving with time in the sample. The probe pulse interacts with the sample, generating different signals (such as absorption spectra, emission spectra, etc.).

[0042] 3. Time Delay

[0043] The time delay between the pump pulse and the probe pulse is very important. By adjusting the time difference between these two pulses, the spectral response of the sample at different time points can be measured, and then the dynamic processes of materials or molecules over time can be studied. These dynamic processes include electron transfer, molecular vibration, intermediate states of chemical reactions, etc.

[0044] 4. Signal Detection and Analysis

[0045] After the probe pulse interacts with the sample, the absorption, emission, or scattering characteristics of the sample will change. By detecting these changes, spectral data of the sample at different time delays can be obtained. By analyzing these data, the dynamic behavior of the sample, reaction pathways, and changes in molecular structure can be revealed.

[0046] 5. Spectrogram and Kinetic Information

[0047] By continuously changing the time delay between the pump pulse and the probe pulse and recording the corresponding spectral response data, a spectrogram in the time domain (time series) is finally obtained. This spectrogram can provide information on the physical or chemical processes of materials or molecules at different time scales, such as electron transitions, molecular conformation changes, energy transfer, etc.

[0048] In the prepared tip-supported single-layer disk 3D structure, the design of TSNOMS enhances the input of optical energy into the metasurface while closing the mechanical and thermal output loss channels. Compared with the metasurface supported by a silicon substrate, the tip support greatly improves the transient signal oscillation modulation ability of the metasurface, significantly improves the optomechanical conversion efficiency and oscillation quality, and the quality factor is improved by several orders of magnitude compared with the ordinary silicon substrate nanodisk array. Optically, TSNOMS has obvious optical resonance absorption valleys, which can more easily couple the pulsed laser energy into the optomechanical system to excite photoacoustic vibrations; thermally, the ultra-small contact area between the tip and the metal nanodisk array greatly reduces the heat loss of the metasurface; mechanically, under the same prestress, the deformation variable of the tip-supported metasurface is larger, which can maximize the closure of the energy channel for phonons to leak to the substrate, making the energy loss close to the theoretical limit.

[0049] The above description is only the preferred embodiments of the present application and is not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application shall be included within the scope of protection of the present application.

Claims

1. A preparation method of a single-layer disc 3D structure supported by a nano-tip, characterized in that It includes the following steps: S1 Deposit a layer of Au film on the silicon wafer; S2 Self-assemble on the surface of the Au film to obtain periodically arranged polymer microspheres; S3 Use reactive ion etching and utilize O2 to reduce the volume of the microspheres; S4 Use reactive ion etching and physically bombard the Au not covered by the microsphere mask with Ar to expose the silicon wafer; S5 Remove the microspheres; S6 Use reactive ion etching and etch the exposed Si layer on the silicon wafer with SF6 to obtain a single-layer disk 3D structure supported by nanometer tips.

2. The preparation method of the single-layer disc 3D structure supported by a nano tip according to claim 1, characterized in that, In S1, a Au film with a thickness of 30 nm was deposited using an electron beam thermal evaporation system, with a deposition rate of 0.4 Å / s, a vacuum degree of 5×10 - 4 Pa, and a voltage of 6 kV.

3. The preparation method of the single-layer disk 3D structure supported by a nano tip according to claim 1, characterized in that In S2, the microspheres are specifically polystyrene microspheres.

4. The preparation method of the single-layer disc 3D structure supported by a nano tip according to claim 1, characterized in that, The etching in S3 specifically includes: Horizontally place the sample in the reactive ion etching chamber, with an etching power of 125 W, a pressure of 20 Pa, an O2 gas flow rate of 50 sccm, and an etching time of 25 s.

5. The preparation method of the single-layer disk 3D structure supported by a nano tip as claimed in claim 1, wherein, S4 specifically includes: Horizontally place the silicon wafer after being processed in S1 - S2 in the reactive ion etching chamber, with an etching power of 150 W, a pressure of 20 Pa, an Ar gas flow rate of 50 sccm, and an etching time of 90 s.

6. The preparation method of the single-layer disk 3D structure supported by a nano tip according to claim 1, characterized in that, In S5, use polyimide tape to physically peel off the polystyrene microspheres.

7. The preparation method of the single-layer disk 3D structure supported by a nano tip according to claim 1, characterized in that S6 specifically includes: Horizontally place the sample in the reactive ion etching chamber, with an etching power of 125 W, a pressure of 20 Pa, an SF6 gas flow rate of 65 sccm, and an etching time of 70 - 90 s.

8. The preparation method of the single-layer disc 3D structure supported by a nano tip according to claim 1, characterized in that, The single-layer disk 3D structure supported by the nanometer tips is used as a nano-optomechanical metasurface.

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