Preparation method of nano needle tip split ring 3D structure periodic array

Abstract

The invention belongs to the field of micro-nano structures, and relates to a preparation method of a nano needle tip split ring 3D structure periodic array. According to the method, after a reflecting layer and a supporting layer are deposited on a silicon substrate, polystyrene nanospheres are self-assembled, the volume of the nanospheres is reduced through reactive ion etching, then two times of inclined magnetron sputtering are carried out, deposited precious metal is etched through a reactive ion etching machine, and the silicon substrate is obtained. And removing the nanosphere mask to obtain the 3D structure periodic array of the nanotip split ring. The method has the characteristics of simple preparation process, good uniformity, high order degree and strong repeatability, and has wide application potential in the fields of SERS (Surface Enhanced Raman Scattering), photoelectric property detection and the like.

Description

Technical Field

[0001] The invention belongs to the field of micro-nano structures and relates to a method for preparing a periodic array of nano needle tip open ring 3D structures. Background Art

[0002] In recent years, the surface plasmon resonance (SPR) effect has attracted much attention due to its unique light-matter interaction characteristics, showing great potential in improving the efficiency of photocatalytic energy conversion. The SPR phenomenon occurs on the surface of metals (such as gold, silver, copper, aluminum, etc.), and their valence electrons oscillate collectively under the action of external fields (such as light). By adjusting the size, composition and morphology of metal nanoparticles, their light absorption properties in the visible to near-infrared region can be precisely controlled, which is expected to broaden the range of light capture. In 2004, Stockman proposed the concept of nanofocusing, which is an important characteristic of surface plasmons. It describes the phenomenon that when surface plasmons propagate along conical metal nanostructures, the energy is highly concentrated at the tip of the cone. This nanofocusing effect makes it possible to form a "hot spot" of electromagnetic field at the tip of the nanostructure for remote excitation and propagation, and the focus size can break through the nanoscale, which has set off a wave of research in recent years internationally. In terms of enhancing light-matter interaction, when SPPs propagate along the conical nanostructure, the energy will converge at the tip height to form a "hot spot" of electromagnetic field. This focusing effect not only has a breakthrough in nanoscale precision, but also can maintain a high-intensity electromagnetic field during remote excitation and propagation, making it possible for highly sensitive detection at the molecular level. In the field of spectral scanning detection, nanotip arrays can be used as probes to achieve remote excitation and precise spectral analysis of molecules, greatly improving the accuracy and sensitivity of detection.

[0003] The nano-tip open ring structure shows unique advantages in the field of near-field optics and nanophotonics. Its ring structure can effectively localize and enhance the electromagnetic field, forming a highly concentrated near-field hotspot, providing an ideal platform for high-sensitivity sensing and super-resolution imaging. By utilizing the electromagnetic field enhancement effect of the nano-tip open ring, ultra-sensitive detection of single molecules or nanoparticles can be achieved, providing new possibilities for breakthroughs in technologies such as surface enhanced Raman spectroscopy (SERS) and fluorescence enhancement.

[0004] Compared with traditional nano-antenna structures, nano-tip split rings have better field enhancement characteristics and more flexible light field control capabilities, and are particularly suitable for nonlinear optics and quantum optics research. However, the precise preparation of nano-tip split rings still faces major challenges. Their complex geometric structure requires extremely high processing accuracy, and it is difficult to ensure the uniformity and consistency of large-scale preparation. These problems have seriously restricted their promotion in industrial applications. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention proposes a method for preparing a periodic array of nano-needle tip open ring 3D structure. The method aims to obtain a nano-needle tip structure with a smaller size, more significant focusing effect and field enhancement effect, and at the same time provides a preparation process with simple steps, large operation space, short preparation cycle and low cost. The periodic array of nano-needle tip open ring 3D structure prepared by this method has the characteristics of large-area controllable construction, good uniformity, high order and strong repeatability, and exhibits excellent localized surface plasmon resonance performance and increased specific surface area characteristics.

[0006] During the preparation process, optical losses are effectively reduced by depositing an aluminum (Al) reflective layer on the silicon wafer. Due to the high lattice matching between aluminum and silicon, its adhesion on the silicon wafer is excellent, making it difficult for the open ring structure to fall off during the subsequent mechanical peeling of the polystyrene (PS) ball. At the same time, silicon dioxide (SiO2) is used as a structural support layer due to its small dielectric constant and high transparency, further improving the optical performance of the nano-needle tip open ring array. In addition, sulfur hexafluoride (SF6) gas is used to anisotropically etch the SiO2 support layer, so that the nano-needle tip open ring forms a semi-suspended state, significantly reducing the dielectric loss, thereby further optimizing the optical performance of the structure. In order to achieve the above purpose, the present application is implemented through the following technical solutions: A method for preparing a periodic array of nano-needle tip open ring 3D structure, comprising the following steps: S1 deposits Al as a reflective layer on the silicon wafer, and then deposits SiO 2 as a support layer, and then self-assemble nanospheres on the support layer as a mask; S2 reduces the volume of the nanospheres by reactive ion etching, and obtains a nanosphere mask with reduced volume on the surface of the silicon wafer; S3 places the silicon wafer with the nanosphere mask surface on a magnetron sputtering sample stage tilted at a certain angle α to deposit the precious metal; S4: After the silicon wafer with the nanosphere mask surface is rotated on the sample stage by a certain angle γ, step S3 is repeated to deposit the noble metal again; S5 uses reactive ion etching to etch the precious metal that is not blocked by the nanosphere mask using argon gas; After S6 etching is completed, the nanospheres are physically peeled off to obtain a periodic array of nanotip open ring 3D structure.

[0007] Preferably, in S2, the reactive ion etching is specifically to use a reactive ion etching method to perform etching on the polystyrene nanospheres. 2 Etching: etching power is 125 W, oxygen pressure is 20 Pa, gas flow rate is 50 sccm, and etching time is 40 s.

[0008] Preferably, S3 specifically includes: placing the silicon wafer on a sample table inclined at 60°, and evacuating the vacuum to 5×10 -4 Pa, argon gas was passed to adjust the sputtering pressure to 0.6 Pa, Au sputtering power to 0.01 KW, sputtering time to 90 s, and a 60 nm gold film was deposited.

[0009] Preferably, in S1, the thickness of the deposited Al is 100 nm; the deposited SiO 2 The thickness is 100 nm, and the deposition rate is 0.2 Å / s; the nanospheres are polystyrene nanospheres with a diameter of 500 nm.

[0010] Preferably, in S5, the etching power is 150 W, the pressure is 20 Pa, the gas flow rate is 50 sccm, and the etching time is 180 s.

[0011] Preferably, in S6, the nanospheres are physically peeled off using polyimide tape.

[0012] Preferably, after S6, the method further includes: step S7, using sulfur hexafluoride gas to etch silicon dioxide to achieve a semi-suspended state of the structure, thereby reducing dielectric loss.

[0013] Preferably, S7 specifically includes the following steps: The etching power used was 125 W, the pressure was 20 Pa, the gas flow rate was 65 sccm, and the etching times were 60 s, 180 s, and 420 s respectively.

[0014] In the present invention, a periodic array of 3D structure of nano-needle tip open rings is prepared. The periodic array has high order, good uniformity and strong repeatability. The preparation method is relatively simple and the preparation cycle is short. It can be effectively replicated and applied on a large scale, which broadens the operational space for subsequent nanostructures. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 Schematic diagram of the preparation process of nano-needle tip open ring.

[0016] Figure 2 This is the SEM comparison of polystyrene nanospheres before and after reactive ion etching.

[0017] Figure 3 This is a SEM image of a periodic array obtained by Ar ion etching after one deposition.

[0018] Figure 4 This is a SEM image of a periodic array obtained by Ar ion etching after two depositions.

[0019] Figure 5 is the reflectance spectrum of the fabricated array.

[0020] Figure 6 The structural hot spot distribution obtained by COMSOL simulation. DETAILED DESCRIPTION

[0021] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0022] like Figure 1 As shown, the method for preparing the periodic array of nano-needle tip open ring 3D structure of this embodiment comprises the following steps: 1) Using electron beam evaporation, 100 nm of aluminum and 100 nm of silicon dioxide were deposited on a silicon substrate at a rate of 0.2 Å / s. 2) Using polystyrene nanospheres as masks, a single-layer hexagonal close-packed array is formed by self-assembly and then the nanosphere mask is transferred to the substrate; 3) Use reactive ion etching, introduce oxygen, set the flow rate to 50sccm, the pressure to 20Pa, the power to 125W, and the RF time to 40s. After waiting for the etching to end, use nitrogen to break the vacuum and obtain a nanosphere mask with a reduced volume, such as Figure 2 As shown; 4) Deposition was performed using magnetron sputtering or electron beam evaporation. The silicon wafer was fixed on a sample stage tilted at 60° and the vacuum was pumped to 5×10 -4 Pa, argon gas, power set to 10W, 60nm gold deposition; 5) Rotate the silicon wafer 90° and repeat the above steps; 6) Place the silicon wafer with the deposited precious metal into the reactive ion etcher, introduce argon gas, set the flow rate to 50sccm, the pressure to 20Pa, the power to 150W, and the RF time to 180s. After the etching is completed, use nitrogen to break the vacuum. Due to the blocking of the nanosphere mask, the exposed precious metal is etched, and the precious metal in the nanosphere positive projection area is retained; 7) The nanosphere mask was physically peeled off using polyimide tape, and a periodic array of nanotip open ring 3D structure was obtained on the silicon wafer, such as Figure 4 As shown; 8) Using SF in reactive ion etching 6 Etching SiO 2 The substrate flow rate was set to 65 sccm, the pressure was set to 20 Pa, the power was set to 125 W, and the etching time was 60 s, 180 s, and 420 s respectively to reduce dielectric loss.

[0023] With the development of advanced nanofabrication technology, a variety of nanostructures can be used to design and fabricate nanoscale plasmon devices. The basic properties of surface plasmons (SPP) and localized surface plasmons (LSP) provide new insights and understandings for the study of optoelectronic devices. Nanostructures such as plasmon tips, gaps, and cavities have been widely studied due to their strong enhanced optical response due to their high-intensity localized fields. Unlike the widely studied nanoholes, the nanotip open ring structure has two nanoscale tips, and there is a strong coupling effect between the surface plasmons (SPP) propagating along the structure and the localized surface plasmon resonance (LSPR) at the open tip, which can be used for SERS and optoelectronic performance detection.

[0024] For etching Si0 2 The reflectance spectra of the samples were tested at different times, e.g. Figure 5 As shown in the figure, in addition to the reflection valley generated by the interband transition of gold at 500nm, two more reflection valleys are generated near 600nm and 900nm. 2 As time goes by, the reflection spectrum has an obvious blue shift. In addition, COMSOL Multiphysics is used to analyze the etching of Si0 2 The sample with a time of 420s was simulated, as shown in Figure 6 As shown in the figure, it can be seen that two high-energy hot spots are generated at the nano tip. Therefore, this structure has good potential in SERS detection and photoelectric performance detection.

Claims

1. A method for preparing a periodic array of nano-needle tip open ring 3D structure, characterized in that: The following steps are involved: S1 deposits Al as a reflective layer on a silicon wafer, then deposits SiO2 as a support layer, and then self-assembles nanospheres on the support layer as a mask; S2 reduces the volume of the nanospheres by reactive ion etching, and obtains a nanosphere mask with reduced volume on the surface of the silicon wafer; S3 places the silicon wafer with the nanosphere mask surface on a magnetron sputtering sample stage tilted at a certain angle α to deposit the precious metal; S4: After the silicon wafer with the nanosphere mask surface is rotated on the sample stage by a certain angle γ, step S3 is repeated to deposit the noble metal again; S5 uses reactive ion etching to etch the precious metal that is not blocked by the nanosphere mask using argon gas; After S6 etching is completed, the nanospheres are physically peeled off to obtain a periodic array of nanotip open ring 3D structure.

2. The method for preparing a periodic array of nano-needle tip open ring 3D structures as claimed in claim 1, characterized in that: In S2, the reactive ion etching is specifically to perform O2 etching on the polystyrene nanospheres using a reactive ion etching method, with an etching power of 125 W, an oxygen pressure of 20 Pa, a gas flow rate of 50 sccm, and an etching time of 40 s.

3. The method for preparing a periodic array of nano-needle tip open ring 3D structures as claimed in claim 1, characterized in that: S3 specifically includes: placing the silicon wafer on a sample stage inclined at 60° and evacuating the sample to a vacuum of 5×10 -4 Pa, argon gas was passed to adjust the sputtering pressure to 0.6 Pa, Au sputtering power to 0.01 KW, sputtering time to 90 s, and a 60 nm gold film was deposited.

4. The method for preparing a periodic array of nano-needle tip open ring 3D structures as claimed in claim 1, characterized in that: In S1, the thickness of the deposited Al is 100 nm; the thickness of the deposited SiO2 is 100 nm, and the deposition rate is 0.2 Å / s; the nanospheres are polystyrene nanospheres with a diameter of 500 nm.

5. The method for preparing a periodic array of nano-needle tip open ring 3D structures as claimed in claim 1, characterized in that: In S5, the etching power is 150 W, the pressure is 20 Pa, the gas flow rate is 50 sccm, and the etching time is 180 s.

6. The method for preparing a periodic array of nano-needle tip open ring 3D structures as claimed in claim 1, characterized in that: In S6, the nanospheres were physically exfoliated using polyimide tape.

7. The method for preparing a periodic array of nano-needle tip open ring 3D structures according to claim 1, characterized in that: After S6, the method further includes: step S7, using sulfur hexafluoride gas to etch silicon dioxide to achieve a semi-suspended state of the structure, thereby reducing dielectric loss.

8. The method for preparing a periodic array of nano-needle tip open ring 3D structures as claimed in claim 7, characterized in that: S7 specifically includes the following steps: The etching power used was 125 W, the pressure was 20 Pa, the gas flow rate was 65 sccm, and the etching times were 60 s, 180 s, and 420 s respectively.

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