A double-layer gold nanopore structure supported by a nanoneedle tip and a preparation method and application thereof

Abstract

This invention belongs to the field of micro / nanostructures, and relates to a nanotip-supported bilayer gold nanoporous structure, its preparation method, and its applications. The preparation method utilizes an electron beam thermal evaporation system, polystyrene microsphere self-assembly technology, and reactive ion etching (RIE) to obtain the nanotip-supported bilayer gold nanoporous structure. This method is not only simple, low-cost, and highly reproducible, but also exhibits good structural stability and high robustness. Compared with monolayer gold nanoporous structures, this invention not only possesses more modes but also displays a complex multimodal response dependent on the pump wavelength.

Description

Technical Field

[0001] This invention belongs to the field of micro-nano structures, and relates to a double-layer gold nanoporous structure supported by nanoneedle tips, its preparation method and application. Background Technology

[0002] Metasurfaces are a new type of material system composed of subwavelength-scale artificial structural units (usually called "atoms") arranged periodically or aperiodically on a two-dimensional plane. By precisely controlling the geometry, size, arrangement, and materials used of the atoms, metasurfaces can achieve flexible manipulation of multiple degrees of freedom, such as electromagnetic wavefront, phase, amplitude, and polarization, even at extremely thin thicknesses. This breaks through the limitations of traditional optical devices in terms of size and function, and is widely used in cutting-edge photonics fields such as planar lenses, holographic imaging, polarization modulators, and stealth devices.

[0003] Although numerous studies have demonstrated the immense potential of metasurfaces in the manipulation of static optical fields, the structure and optical response of traditional metasurfaces become fixed once they are fabricated at the nanoscale, making them difficult to adapt to external stimuli or environmental changes. This "static manipulation" characteristic severely restricts their further expansion in practical applications such as adaptive optics, programmable optical devices, dynamic imaging, and sensing. To address these issues, researchers have recently proposed and continuously developed the concept of "reconfigurable metasurfaces," which allows for dynamic, real-time control of the optical properties of metasurfaces by introducing tunable materials or external excitation methods.

[0004] Depending on the external excitation method, reconfigurable metasurfaces can be classified into electrically controlled, thermally controlled, mechanically controlled, phase-change material driven, and optically controlled types. Among them, all-optically driven reconfigurable metasurfaces have attracted widespread attention due to their advantages such as no electrode wiring required, ultrafast response speed, non-contact manipulation, and high spatial resolution. This type of metasurface can achieve rapid control of optical response within picosecond or even femtosecond timescales by exciting changes in carrier concentration, modulating local refractive index, or inducing structural phase transitions in materials through pump light. Therefore, all-optically driven reconfigurable metasurfaces have significant potential in the development of highly integrated, low-energy-consumption, and intelligent photonic devices. Constructing such platforms with stable structures, fast responses, and precise controllability has become one of the current hot topics and challenges in optical device research. However, despite numerous breakthroughs in device design and material response, this technology still faces key challenges: at the experimental level, the inherent vibrational modes induced by external field excitation in traditional structures lack controllable switching capabilities; at the theoretical level, the spatiotemporal reconstruction mechanism under multimodal coupling has not yet been fully established. These issues significantly limit the practical expansion of all-optically driven reconfigurable metasurfaces in multifunctional dynamic response applications. Summary of the Invention

[0005] To address the insufficient controllability of intrinsic vibrational mode switching on traditional metasurfaces under external field excitation, this invention proposes a nanotip-supported bilayer gold nanopore structure and its fabrication method. This method, while maintaining high photomechanical conversion efficiency and oscillation quality, induces a spatially gradient-distributed photothermal stress field within the metasurface through pump wavelength modulation, thereby achieving multi-mode controllable switching on femtosecond to picosecond timescales. Furthermore, this invention provides a simple, efficient, short-cycle, and low-cost fabrication method. The resulting nanotip-supported bilayer gold nanopore structure exhibits characteristics of large-area controllable fabrication, high uniformity, long-range order, and strong repeatability.

[0006] To achieve the above objectives, the present invention adopts the following solution:

[0007] A method for preparing a bilayer gold nanoporous structure supported by nanoneedle tips includes the following steps:

[0008] S1 self-assembles into periodically arranged polystyrene microspheres on the upper surface of a silicon wafer;

[0009] S2 uses reactive ion etching and utilizes O2 to reduce the volume of the microspheres;

[0010] S3 deposits an Au film on the upper surface of the silicon wafer;

[0011] S4 removes the microspheres, resulting in an Au film with uniformly arranged nanopores on a silicon wafer;

[0012] S5 uses reactive ion etching to etch the silicon layer exposed by the nanopores on the upper surface of the silicon wafer using SF6. By controlling the etching time, an Au film with uniformly arranged nanopores supported by silicon nanostages is obtained, which serves as the first Au film.

[0013] S6 deposits a SiO2 film on the upper surface of the product obtained in step S5, and then deposits an Au film on the SiO2 film as a second Au film. The two Au films have the same thickness.

[0014] S7 uses reactive ion etching to simultaneously etch silicon nanostages and the SiO2 layer sandwiched between two Au films using SF6. After etching, a double-layer Au film with uniformly arranged nanopores is obtained, supported by silicon nanoparticle tips. The nanopores on the two Au films are positioned one-to-one, and the support points for the nanoparticle tips to support the Au films are located between four adjacent nanopores on the lower surface of the first Au film.

[0015] Preferably, in S1, the polystyrene microspheres have a diameter of 500 nm.

[0016] Preferably, S2 specifically includes: placing the sample horizontally in the reactive ion etching chamber, setting the etching gas to O2, flow rate to 50 sccm, working pressure to 20 Pa, power to 125 W, and etching time to 40 s.

[0017] Preferably, the deposition of an Au film in step S3 specifically includes: Au deposition using an electron beam thermal evaporation system at a pressure of 5 × 10⁻⁶. -4 Pa, voltage 6 kV, deposition rate 0.4 Å / s, deposition thickness 30 nm.

[0018] Preferably, in S4, the removal of microspheres specifically involves physically peeling the polystyrene microspheres using polyimide tape.

[0019] Preferably, the SF6 etching described in S5 specifically includes: placing the silicon wafer horizontally in the reactive ion etching chamber, setting the etching gas to SF6, a flow rate of 65 sccm, a working pressure of 20 Pa, a power of 125 W, and an etching time of 45 s.

[0020] Preferably, in step S6, the deposition of a SiO2 film specifically includes: depositing SiO2 using an electron beam thermal evaporation system at a pressure of 5 × 10⁻⁶. -4 Pa, voltage 6 kV, SiO2 deposition rate 0.8 Å / s, deposition thickness 60 nm; the deposition of an Au film specifically includes: Au deposition using an electron beam thermal evaporation system; deposition rate 0.4 Å / s, deposition thickness 30 nm.

[0021] Preferably, in S7, the simultaneous etching of the silicon nanostage and the SiO2 layer sandwiched between the two Au films using SF6 specifically includes: placing the product obtained in S6 horizontally in the reactive ion etching chamber, setting the etching gas to SF6, a flow rate of 65 sccm, a working pressure of 20 Pa, a power of 125 W, and an etching time of 60 s.

[0022] The present invention also provides a double-layer gold nanoporous structure supported by nanoneedle tips, which is prepared by the aforementioned preparation method.

[0023] This invention also provides an application of the aforementioned nanotip-supported bilayer gold nanopore structure to metasurfaces, comprising the following steps:

[0024] Change the wavelength of the pump light irradiating the metasurface;

[0025] Changing the resonance mode of metasurfaces within the femtosecond to picosecond timescale range;

[0026] Under 340 nm pump excitation, a global thermal stress distribution is generated, exciting vibrational modes of 2.4 GHz, 3.0 GHz, and 4.6 GHz; under 690 nm excitation, modes of 4.2 GHz, 5.0 GHz, and 7.6 GHz are selectively excited via the LSPR effect; and under 850 nm excitation, resonant modes of 4.0 GHz, 5.0 GHz, and 7.4 GHz are generated using the nanopore gap mode.

[0027] Compared with the single-layer Au nanopore structure supported by nanoneedle tips, this invention not only supports more vibrational modes, but also induces a photothermal stress field with a spatial gradient distribution inside the metasurface by in-situ controlling the pump light wavelength, thereby achieving controllable switching of multiple modes within the femtosecond to picosecond timescale. Attached Figure Description

[0028] Figure 1 A schematic diagram of the process for preparing a bilayer Au nanoporous structure supported by nanoneedle tips.

[0029] Figure 2 A 3D schematic diagram of a double-layer Au nanopore structure supported by nanoneedle tips.

[0030] Figure 3 A schematic diagram of the cross-section of a double-layer Au nanoporous structure supported by nanoneedle tips.

[0031] Figure 4 SEM image of a double-layer Au nanoporous structure supported by nanoneedle tips.

[0032] Figure 5 The reflectance spectra of the bilayer Au nanopore structure supported by nanoneedles are obtained from experimental measurements (black curve) and finite element simulation (COMSOL, red curve).

[0033] Figure 6 The near-field electric field intensity distribution simulated for a bilayer Au nanoporous structure supported by nanoneedles.

[0034] Figure 7 Transient absorption spectrum of a bilayer Au nanoporous structure supported by nanoneedle tips under 340 nm pump light.

[0035] Figure 8 for Figure 7 The spectrum obtained by Fast Fourier Transform (FFT) (black curve) and the simulation results (red curve).

[0036] Figure 9 Transient absorption spectrum of a bilayer Au nanoporous structure supported by nanoneedle tips under 690 nm pump light.

[0037] Figure 10 for Figure 9The spectrum obtained by Fast Fourier Transform (FFT) (black curve) and the simulation results (red curve).

[0038] Figure 11 Transient absorption spectrum of a bilayer Au nanoporous structure supported by nanoneedle tips under 850 nm pump light.

[0039] Figure 12 for Figure 11 The spectrum obtained by Fast Fourier Transform (FFT) (black curve) and the simulation results (red curve). Detailed Implementation

[0040] To further understand this application, the following detailed description of the method for preparing a double-layer Au nanopore structure supported by nanoneedle tips provided in this application is provided in conjunction with embodiments. The scope of protection of this application is not limited to the following embodiments.

[0041] like Figure 1 A nanoneedle-tip supported bilayer gold nanoporous structure and its preparation method, comprising the following steps:

[0042] S1 uses a hydrophilic culture dish to obtain large-area polystyrene microspheres with periodic arrangement on a cleaned silicon wafer surface through self-assembly technology.

[0043] S2 uses reactive ion etching and utilizes O2 to reduce the volume of microspheres;

[0044] S3 uses an electron beam evaporation system to deposit an Au film;

[0045] S4 removes polystyrene microspheres, resulting in a large area of ​​uniformly arranged Au nanopores on a silicon wafer;

[0046] S5 uses reactive ion etching, employing SF6 to etch the exposed Si layer, and controls the etching time to obtain a single-layer Au nanopore supported by silicon nanostages.

[0047] S6 uses an electron beam evaporation system to deposit a SiO2 film, followed by an Au film. In order to induce a photothermal stress field with a spatial gradient distribution inside the metasurface, thereby enabling controllable switching of multiple modes in the femtosecond to picosecond timescale, the Au film obtained in this step is required to have the same thickness as the Au film obtained in the previous step.

[0048] S7 uses reactive ion etching (RIE) to simultaneously etch silicon nanostages and SiO2 layers using SF6. After etching, a bilayer gold nanopore structure supported by nanoneedle tips is obtained. The structure of the prepared product is shown below. Figure 2 and Figure 3 As shown.

[0049] Preferably, in step S1, the diameter of the polystyrene microspheres is 500 nm.

[0050] Preferably, in step S2, the etching process specifically includes the following steps: placing the sample horizontally in the chamber of the reactive ion etching instrument, setting the etching gas to O2, the flow rate to 50 sccm, the working pressure to 20 Pa, the power to 125 W, and the etching time to 40 s.

[0051] Preferably, in step S3, the coating process specifically includes the following steps: Au deposition using an electron beam thermal evaporation system at a pressure of 5 × 10⁻⁶. -4 Pa, voltage 6 kV, deposition rate 0.4 Å / s, deposition thickness 30 nm.

[0052] Preferably, in step S5, the etching process specifically includes the following steps: placing the sample horizontally in the reactive ion etching chamber, setting the etching gas to SF6, flow rate to 65 sccm, working pressure to 20 Pa, power to 125 W, and etching time to 45 s.

[0053] Preferably, in step S6, the coating process specifically includes the following steps: depositing SiO2 and Au using an electron beam thermal evaporation system at a pressure of 5 × 10⁻⁶. -4 Pa, voltage 6 kV, SiO2 deposition rate 0.8 Å / s, deposition thickness 60 nm; Au deposition rate 0.4 Å / s, deposition thickness 30 nm.

[0054] Preferably, in step S7, the etching process specifically includes the following steps: placing the sample horizontally in the reactive ion etching chamber, setting the etching gas to SF6, flow rate to 65 sccm, working pressure to 20 Pa, power to 125 W, and etching time to 60 s. Example

[0055] First, 500 nm polystyrene microspheres were transferred to the cleaned silicon wafer surface using a self-assembly technique, ensuring a large-area, uniform arrangement of the microspheres. Then, reactive ion etching was performed, first introducing O2 to reduce the volume of the polystyrene microspheres at a flow rate of 50 sccm, an operating pressure of 20 Pa, a power of 125 W, and an etching time of 40 s. Finally, a 30 nm Au film was deposited using an electron beam thermal evaporation system at a pressure of 5 × 10⁻⁶. -4At a pressure of 6 kV and a voltage of 6 kV, the deposition rate was 0.4 Å / s, followed by physical removal of the polystyrene microspheres. Then, reactive ion etching was performed on the exposed Si substrate using SF6 gas at a flow rate of 65 sccm, a working pressure of 20 Pa, a power of 125 W, and an etching time of 45 s. Next, a 60 nm SiO2 film and a 30 nm Au film were deposited again using an electron beam thermal evaporation system, with a SiO2 deposition rate of 0.8 Å / s and an Au deposition rate of 0.4 Å / s. Finally, reactive ion etching was performed on both the Si abutments and the SiO2 layer using SF6 gas at a flow rate of 65 sccm, a working pressure of 20 Pa, a power of 125 W, and an etching time of 60 s. Figure 4 As shown.

[0056] Subsequently, the reflectance spectrum of the bilayer Au nanopore structure supported by the nanoneedle tip was obtained by spectrometer, showing three absorption valleys at 500 nm, 690 nm, and 840 nm. Figure 5 (Black curve). Based on the finite element method (FEM) numerical simulation (using COMSOL Multiphysics software), the experimental and simulation results are as follows ( Figure 5 The red curve (the curve) almost perfectly matches the pattern. To further elucidate the physical mechanisms of these patterns, we... Figure 6 The diagram shows the near-field distribution of electric field intensity at various wavelengths. The 840 nm resonant absorption corresponds to the gap mode of the interlayer groove, the 690 nm absorption valley originates from the dipole localized surface plasmon resonance (LSPR) mode of the nanopores in the upper and lower gold layers, and the resonance at 500 nm is a characteristic of interband transitions in gold.

[0057] Subsequently, using pump-probe technology, the pump light was tuned to 340 nm, and we obtained the transient absorption spectrum of the bilayer Au nanopore structure supported by nanoneedle tips, such as... Figure 7 As shown. Fast Fourier Transform (FFT) analysis revealed three resonance peaks at 2.4 GHz, 3.0 GHz, and 4.6 GHz, as... Figure 8 As shown (black curve). Finally, the nanomechanical oscillation performance of the double-layer Au nanopore structure supported by nanoneedle tips was simulated using the COMSOL Multiphysics solid mechanics module. The simulation results of nanomechanical oscillation are as follows (…). Figure 8 The frequency (shown by the solid red line) closely matches the resonance frequency of the Fourier analysis spectrum. Example

[0058] The difference from Example 1 is that, when using the pump-probe technique for testing, the pump light was tuned to 690 nm, and a transient absorption spectrum was obtained, as shown below. Figure 9As shown. FFT analysis revealed three resonance peaks at 4.2 GHz, 5.0 GHz, and 7.6 GHz, as... Figure 10 As shown (black curve). Simulation calculations were performed on its nanomechanical oscillation performance, and the simulation results of the nanomechanical oscillation are as follows (…). Figure 10 The resonant frequency (shown by the solid red line) remains highly consistent with the Fourier analysis spectrum. Example

[0059] The difference from Example 1 is that, when using the pump-probe technique for testing, the pump light was tuned to 850 nm, and a transient absorption spectrum was obtained, as shown below. Figure 11 As shown. FFT analysis revealed three resonance peaks at 4.0 GHz, 5.0 GHz, and 7.4 GHz, as... Figure 12 As shown (black curve). Simulation calculations were performed on its nanomechanical oscillation performance, and the simulation results of the nanomechanical oscillation are as follows (…). Figure 12 The resonant frequency (shown by the solid red line) remains highly consistent with the Fourier analysis spectrum.

[0060] Experiments and theoretical simulations have demonstrated that the fabricated bilayer Au nanopore structure supported by nanoneedles can alter its vibrational and optical properties according to the wavelength of light on extremely fast timescales (from femtoseconds to picoseconds). Different colors of laser pump light generate different thermal stress distributions within the structure, thereby exciting different vibrational modes. Specifically, under 340 nm pump excitation, a global thermal stress distribution is generated, primarily exciting vibrational modes at 2.4 GHz, 3.0 GHz, and 4.6 GHz; under 690 nm excitation, 4.2 GHz, 5.0 GHz, and 7.6 GHz modes are selectively excited via the LSPR effect; and under 850 nm excitation, 4.0 GHz, 5.0 GHz, and 7.4 GHz resonant modes are generated using the nanopore gap mode.

[0061] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for preparing a bilayer gold nanoporous structure supported by nanoneedle tips, characterized in that, Includes the following steps: S1 self-assembles into periodically arranged polystyrene microspheres on the upper surface of a silicon wafer; S2 uses reactive ion etching and utilizes O2 to reduce the volume of the microspheres; S3 deposits an Au film on the upper surface of the silicon wafer; S4 removes the microspheres, resulting in an Au film with uniformly arranged nanopores on a silicon wafer; S5 uses reactive ion etching to etch the silicon layer exposed by the nanopores on the upper surface of the silicon wafer using SF6. By controlling the etching time, an Au film with uniformly arranged nanopores supported by silicon nanostages is obtained, which serves as the first Au film. S6 deposits a SiO2 film on the upper surface of the product obtained in step S5, and then deposits an Au film on the SiO2 film as a second Au film. The two Au films have the same thickness. S7 uses reactive ion etching, which uses SF6 to simultaneously etch silicon nanostages and the SiO2 layer sandwiched between two Au films. After etching, a double-layer Au film with uniformly arranged nanopores is obtained, supported by silicon nanoneedles. The nanopores on the two Au films are positioned one-to-one, and the support points for the nanoneedles to support the Au films are located between four adjacent nanopores on the lower surface of the first Au film.

2. The method for preparing the nanoneedle-tip-supported bilayer gold nanoporous structure as described in claim 1, characterized in that, In S1, the polystyrene microspheres have a diameter of 500 nm.

3. The method for preparing the nanoneedle-tip-supported bilayer gold nanoporous structure as described in claim 1, characterized in that, S2 specifically includes: placing the sample horizontally in the reactive ion etching chamber, setting the etching gas to O2, flow rate to 50 sccm, working pressure to 20 Pa, power to 125 W, and etching time to 40 s.

4. The method for preparing the bilayer gold nanoporous structure supported by nanoneedle tips as described in claim 1, characterized in that, The deposition of an Au film as described in S3 specifically includes: Au deposition using an electron beam thermal evaporation system at a pressure of 5 × 10⁻⁶. -4 Pa, voltage 6 kV, deposition rate 0.4 Å / s, deposition thickness 30 nm.

5. The method for preparing the bilayer gold nanoporous structure supported by nanoneedle tips as described in claim 1, characterized in that, In S4, the removal of microspheres specifically involves physically peeling off the polystyrene microspheres using polyimide tape.

6. The method for preparing the nanoneedle-tip-supported bilayer gold nanoporous structure as described in claim 1, characterized in that, The SF6 etching described in S5 specifically includes: placing the silicon wafer horizontally in the reactive ion etching chamber, setting the etching gas to SF6, a flow rate of 65 sccm, a working pressure of 20 Pa, a power of 125 W, and an etching time of 45 s.

7. The method for preparing the nanoneedle-tip-supported bilayer gold nanoporous structure as described in claim 1, characterized in that, In S6, The deposition of a SiO2 film specifically includes: SiO2 deposition using an electron beam thermal evaporation system at a pressure of 5 × 10⁻⁶. -4 Pa, voltage 6 kV, SiO2 deposition rate 0.8 Å / s, deposition thickness 60 nm; The deposition of an Au film specifically includes: Au deposition using an electron beam thermal evaporation system; a deposition rate of 0.4 Å / s and a deposition thickness of 30 nm.

8. The method for preparing the bilayer gold nanoporous structure supported by nanoneedle tips as described in claim 1, characterized in that, In S7, the simultaneous etching of silicon nanostages and SiO2 layer sandwiched between two Au films using SF6 specifically includes: placing the product obtained in S6 horizontally in the reactive ion etching chamber, setting the etching gas to SF6, flow rate to 65 sccm, working pressure to 20 Pa, power to 125 W, and etching time to 60 s.

9. A double-layer gold nanoporous structure supported by nanoneedle tips, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 8.

10. The application of the nanoneedle-tip-supported bilayer gold nanoporous structure as described in claim 9, characterized in that, When applied to metasurfaces, the following steps are included: Change the wavelength of the pump light irradiating the metasurface; Changing the resonance mode of metasurfaces within the femtosecond to picosecond timescale range; Under 340 nm pump excitation, a global thermal stress distribution is generated, exciting vibrational modes of 2.4 GHz, 3.0 GHz, and 4.6 GHz; under 690 nm excitation, modes of 4.2 GHz, 5.0 GHz, and 7.6 GHz are selectively excited via the LSPR effect; and under 850 nm excitation, resonant modes of 4.0 GHz, 5.0 GHz, and 7.4 GHz are generated using the nanopore gap mode.

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