A method for preparing and exfoliating a flexible porous silicon carbide film

Abstract

This invention discloses a method for preparing and peeling flexible porous silicon carbide thin films, belonging to the field of single-crystal flexible film manufacturing technology. The method includes: Step 1: Pre-treating a SiC wafer; Step 2: Constructing an electrode system, comprising a working electrode and a counter electrode, wherein the working electrode is the pre-treated SiC wafer; placing the electrode system in an alkaline electrolyte; and connecting the electrode system to an electrochemical workstation; Step 3: Applying an electric field to the SiC wafer through the electrochemical workstation while simultaneously irradiating the surface of the SiC wafer with light, causing a porous structure to form on the surface of the SiC wafer; Step 4: Applying a high voltage to peel off the porous structure, obtaining a flexible porous silicon carbide thin film. This invention's preparation and peeling method is simple and easy to implement, effectively preparing flexible porous silicon carbide thin films at a low cost and with simple operation, without requiring mechanical force or complex vacuum equipment, and possessing good safety and environmental adaptability.

Description

Technical Field

[0001] This invention relates to the field of single-crystal flexible film manufacturing technology, and in particular to a method for preparing and peeling flexible porous silicon carbide thin films. Background Technology

[0002] Silicon carbide (SiC), as a wide bandgap semiconductor material, has become a key material for high-frequency, high-voltage, high-power power electronic devices, optoelectronic devices, and microelectromechanical systems due to its excellent physical, chemical, electrical, and thermal properties (such as high breakdown field strength, high electron mobility, strong chemical inertness, and high thermal conductivity). It is widely used in electric vehicle power modules, photovoltaic inverters, photodetectors, light-emitting diodes, and data centers.

[0003] Since the luminescent properties of porous silicon attracted widespread attention, various porous semiconductor materials (including porous gallium arsenide, porous gallium nitride, and porous SiC) have also been extensively studied. Compared to porous silicon, porous silicon carbide, with its high specific surface area, enhanced photoluminescence quantum yield, stronger chemical inertness, and temperature stability, has enormous application potential in fields such as epitaxial growth substrates, chemical / biological sensors, biocompatible films, pollutant adsorption, supercapacitors, photocatalytic devices, and flexible electronic devices.

[0004] Currently, porous silicon carbide fabrication technology mainly employs dry etching techniques, such as reactive ion etching and inductively coupled plasma etching. While these methods offer high etching rates, they suffer from high equipment costs, complex processes, and stringent operational requirements, making it difficult to meet the demands for large-scale, low-cost fabrication. Furthermore, the bombardment of high-energy ions can cause irreversible damage to the material's surface and subsurface, affecting the performance and reliability of subsequent devices. Moreover, even if porous silicon carbide structures are successfully fabricated using these methods, the complete exfoliation of the porous silicon carbide film for application in related fields (such as flexible electronic devices) remains a challenge. Traditional exfoliation methods mainly include stress-induced self-exfoliation, adhesion / tear methods, laser cutting, and wire cutting. Stress-induced self-peeling relies on the release of internal stress between the film and the substrate, but it requires high precision in stress control and is prone to uncontrollable cracks or film warping, making it difficult to obtain structurally intact porous silicon carbide films. Adhesion / peeling methods, which involve peeling off layers after adhesion with tape or polymer film, suffer from uneven adhesion and residual contamination, especially on rough or porous surfaces. While laser cutting and wire cutting can precisely control the thickness and peeling position of the porous layer to some extent, they still have significant limitations when applied to porous silicon carbide materials. On the one hand, due to the numerous pores within porous SiC, its overall mechanical strength is significantly lower than that of dense SiC, making it highly susceptible to failures such as localized cracking and fragmentation due to mechanical traction or vibration during wire cutting. On the other hand, the instantaneous high temperature generated by the high-energy laser beam in the focusing area during laser cutting can cause localized thermal damage, pore collapse, or microcrack propagation around the porous structure, thus affecting the integrity of the peeled layer and the performance of subsequent devices. Therefore, although laser cutting and wire cutting perform well in the processing of other materials, their feasibility and adaptability are still greatly limited for porous silicon carbide films with fragile structures and complex pore size distributions.

[0005] Therefore, existing technologies still need to be improved and developed. Summary of the Invention

[0006] Currently, the preparation of high-quality, peelable porous silicon carbide films still faces many challenges. The high hardness and chemical inertness of silicon carbide make its processing and surface modification exceptionally difficult, which is a major obstacle limiting the further application and promotion of porous silicon carbide films. The purpose of this invention is to provide a method for preparing and peeling porous silicon carbide films, aiming to solve the problems of complex preparation processes and low peeling efficiency in existing technologies.

[0007] The technical solution of the present invention is as follows: A method for preparing and peeling a flexible porous silicon carbide thin film, comprising: Step 1: Pre-process the SiC wafer; Step 2: Construct an electrode system, which includes a working electrode and a counter electrode. The working electrode is the pretreated SiC sheet. Place the electrode system in an alkaline electrolyte and connect the electrode system to an electrochemical workstation. Step 3: Apply an electric field to the SiC wafer using the electrochemical workstation, and simultaneously illuminate the surface of the SiC wafer to form a flexible porous silicon carbide thin film on the surface of the SiC wafer; Step 4: Apply a high voltage to peel off the flexible porous silicon carbide film.

[0008] Optionally, step one specifically includes: ultrasonically cleaning the SiC wafer sequentially in acetone, anhydrous ethanol, and deionized water, each step lasting 5-10 minutes; after the ultrasonic cleaning is completed, the SiC wafer is placed in a dry nitrogen stream to dry.

[0009] Optionally, in step two, the alkaline electrolyte is prepared by dissolving an alkaline electrolyte in water, wherein the alkaline electrolyte is at least one selected from potassium hydroxide, cesium hydroxide, rubidium hydroxide, sodium hydroxide, and lithium hydroxide, and the concentration of the alkaline electrolyte is 0.01-3 mol / L. -1 .

[0010] Optionally, in step two, hydrofluoric acid, ammonium fluoride, or sodium fluoride are added to the alkaline electrolyte.

[0011] Optionally, in step two, the electrode system further includes a reference electrode, the counter electrode is a platinum wire, and the reference electrode is a standard mercury oxide electrode.

[0012] Optionally, in step three, the electrochemical control mode of the electrochemical workstation is constant current, voltage step, linear voltage scan, multi-potential step method, or pulse voltage.

[0013] Optionally, in step three, the surface of the SiC wafer is illuminated with white light or ultraviolet light, wherein the intensity of the white light is 300~1000 mW cm⁻¹. -2 The intensity of ultraviolet light is 50~500 mW cm⁻¹ -2 .

[0014] Optionally, in step three, a constant low voltage of 4-10 V is applied to the SiC wafer through the electrochemical workstation.

[0015] Optionally, in step four, the high voltage is 15-40 V and lasts for several seconds to several minutes.

[0016] Optionally, step four further includes: after the flexible porous silicon carbide film is peeled off, the flexible porous silicon carbide film is taken out from the alkaline electrolyte, rinsed with deionized water, and then dried to obtain the flexible porous silicon carbide film.

[0017] Beneficial Effects: This invention provides a method for preparing and peeling off porous silicon carbide thin films based on photoelectrochemical methods. This method utilizes the synergistic effect of light and electric field to achieve the preparation and subsequent peeling of flexible porous SiC thin films under mild conditions in an alkaline electrolyte. Compared with existing technologies, this invention has the following technical advantages: (1) Simple operation, low cost, and low equipment requirements The entire process requires only conventional electrochemical equipment and a light source system, without the need for high-energy plasma equipment, vacuum systems, or cutting equipment; the process steps are simple and highly repeatable; the chemicals used are inexpensive; the equipment is small in size; and the entire system is easy to integrate into existing semiconductor microfabrication platforms.

[0018] (2) Achieving controllable adjustment of flexible porous silicon carbide thin films By adjusting photoelectrochemical operating parameters, such as voltage (e.g., 4-10 V), light intensity, and reaction time, the dynamic balance between the oxidation rate and dissolution rate on the SiC film surface can be effectively controlled, thereby obtaining porous silicon carbide films with tunable pore morphology, pore density, and porous layer thickness. This tunability allows the present invention to meet the application needs of different fields, such as high specific surface area structures suitable for sensors, and uniform porous layers suitable for epitaxial growth.

[0019] (3) High-quality peeling effect After the porous silicon carbide thin film is prepared, a short-term high voltage (e.g., 15-40 V) is applied to induce pore wall rupture through an electric field, and the generated gas enables rapid self-peeling of the film. This peeling method completely avoids mechanical intervention, significantly reducing the film breakage rate. The resulting peeled flexible porous silicon carbide thin film has a neat surface and clear boundaries. The resulting flexible porous silicon carbide thin film combines large area and integrity, maintains excellent flexibility, and has a complete porous structure, making it suitable for cutting-edge fields such as flexible electronic devices, MEMS devices, optoelectronic devices, and biosensors, and possessing broad prospects for industrial application. Attached Figure Description

[0020] Figure 1 This is a schematic diagram illustrating a method for preparing and peeling a flexible porous silicon carbide thin film according to the present invention.

[0021] Figures 2-6 These are scanning electron microscope images of the flexible porous silicon carbide films prepared in Examples 1-5.

[0022] Figure 7The Raman scattering spectra of the flexible porous silicon carbide films prepared in Examples 1-5 are shown.

[0023] Figure 8 This is a flexible bending diagram of the flexible porous silicon carbide film after peeling in Example 1.

[0024] Figure 9 The graph shows the response current of the flexible porous silicon carbide thin film in Example 1 under different light irradiation conditions.

[0025] Figure 10 The graph shows the adsorption effect of the flexible porous silicon carbide film on methylene blue at different times after it has been placed in an aqueous solution of methylene blue in Example 1. Detailed Implementation

[0026] This invention provides a method for preparing and peeling flexible porous silicon carbide thin films. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0027] To address the problems of complex equipment, high energy consumption, low peeling efficiency, uncontrollable peeling process, and easy film damage in the preparation and peeling of porous silicon carbide films in existing technologies, this invention provides a safe, simple, and controllable method for preparing and peeling flexible porous silicon carbide films. The method includes: Step 1: Pre-process the SiC wafer; Step 2: Construct an electrode system, which includes a working electrode and a counter electrode. The working electrode is the pretreated SiC sheet. Place the electrode system in an alkaline electrolyte and connect the electrode system to an electrochemical workstation. Step 3: Apply an electric field to the SiC wafer using the electrochemical workstation, and simultaneously illuminate the surface of the SiC wafer to form a flexible porous silicon carbide thin film on the surface of the SiC wafer; Step 4: Apply a high voltage to peel off the flexible porous silicon carbide film.

[0028] In this embodiment of the invention, a single-crystal SiC wafer is first placed in an alkaline electrolyte. An electric field (such as a constant voltage) is applied through an external power source, while simultaneously irradiating the SiC wafer with white light or ultraviolet light, causing photogenerated electron-hole pairs to form on the SiC wafer surface. The generated holes cause electrochemical anodic oxidation on the SiC wafer surface, forming an oxide layer. Subsequently, the oxide layer dissolves in the alkaline electrolyte, forming a uniformly structured porous SiC film. When a constant voltage is applied, the oxidation rate and dissolution process on the SiC wafer surface can be balanced by controlling the applied voltage and light intensity. By controlling the photoelectrochemical reaction time, the thickness of the flexible porous silicon carbide film on the SiC wafer surface can be effectively controlled. After a period of photoelectrochemical reaction, the low voltage is adjusted to a high voltage. At this point, a violent reaction occurs at the interface between the flexible porous silicon carbide film and the unreacted area. Under the action of high voltage, the porous SiC pore walls are very thin and fragile. Under the action of a large number of bubbles, the flexible porous silicon carbide film is successfully peeled off and floats on the electrolyte surface. At this point, the flexible porous silicon carbide film can be collected using a suitable tool. This method can easily and quickly prepare flexible porous silicon carbide films and successfully peel them off, thus effectively solving the problems of traditional dry etching for preparing porous silicon carbide and the difficulty in peeling off the films.

[0029] The preparation and exfoliation methods of this invention are simple and easy to implement, enabling the effective preparation of flexible porous silicon carbide films at a low cost and with simple operation. This is achieved without the use of highly toxic hydrofluoric acid solutions, mechanical force, or complex vacuum equipment, and offers good safety and environmental adaptability. This invention allows for effective control over the thickness and exfoliation interface of the porous silicon carbide film, resulting in structurally complete flexible porous silicon carbide films. This meets the requirements of sensors, optoelectronic devices, epitaxial substrates, and photocatalysis for high-quality flexible porous silicon carbide films.

[0030] In one embodiment, step one specifically includes: ultrasonically cleaning the SiC wafer sequentially in acetone, anhydrous ethanol, and deionized water, each step lasting 5-10 minutes; after the ultrasonic cleaning is completed, the SiC wafer is placed in a dry nitrogen stream to dry.

[0031] In this embodiment of the invention, the SiC wafer (primarily used as a substrate) is first subjected to a standard cleaning process to remove surface organic contaminants and particulate impurities. Specifically, ultrasonic cleaning is performed sequentially in acetone, anhydrous ethanol, and deionized water, each step lasting 5-10 minutes. After cleaning, the SiC wafer is dried in a dry nitrogen stream to ensure its surface is clean and dry, providing a good foundation for subsequent etching reactions.

[0032] In one embodiment, step two specifically includes: constructing a dual-electrode system, the dual-electrode system including a working electrode and a counter electrode, wherein the pretreated SiC sheet serves as the working electrode (anode) and the platinum wire serves as the counter electrode (cathode), placing the dual-electrode system in an alkaline electrolyte, and connecting the dual-electrode system to an electrochemical workstation.

[0033] In one embodiment, step two specifically includes: constructing a three-electrode system, which includes a working electrode, a counter electrode, and a reference electrode, wherein the pretreated SiC sheet serves as the working electrode (anode), the platinum wire serves as the counter electrode (cathode), and the reference electrode is a standard mercury oxide electrode (Hg / HgO). The three-electrode system is placed in an alkaline electrolyte, and the three-electrode system is connected to an electrochemical workstation.

[0034] The alkaline electrolyte used in this invention has good adjustability. The alkaline electrolyte can be any alkaline electrolyte other than potassium hydroxide (KOH), such as cesium hydroxide (CsOH), rubidium hydroxide (RbOH), sodium hydroxide (NaOH), lithium hydroxide (LiOH), etc. Different cations (K... + Cs + 、Rb + Na + Li + This method exhibits specificity for SiC etching, enabling precise control of pore morphology and selective adjustment of etching rate, which can be selected according to the desired pore structure. The alkaline system described in this embodiment of the invention achieves the preparation of flexible porous silicon carbide films while possessing high safety and environmental friendliness. To accelerate the preparation or stripping process of flexible porous silicon carbide films, hydrofluoric acid (HF), ammonium fluoride (NH4F), sodium fluoride (NaF), and other fluoride-containing substances can be introduced into the alkaline electrolyte. This is because fluoride ions can significantly enhance the chemical etching activity and stripping effect of silicon carbide.

[0035] In one embodiment, step three specifically includes: applying a constant low voltage (controllable within the range of 4-10 V) to the SiC wafer using an electrochemical workstation, while simultaneously subjecting the SiC wafer surface to uniform illumination, thereby forming a flexible porous silicon carbide thin film on the SiC wafer surface. The light source can be white light (such as simulated sunlight, with an intensity typically ranging from 300 to 1000 mW / cm²). -2 For example, 800mW cm -2 Or ultraviolet light (typical wavelength 340 nm, light intensity approximately 50~500 mW cm⁻¹). -2 For example, 150 mW cm -2 Under the combined effect of light and electric field, the photoelectrochemical anodizing reaction is initiated.

[0036] Under the combined influence of light and an electric field, a large number of photogenerated electron-hole pairs are generated on the surface of the SiC wafer. Under the applied electric field, the photogenerated holes migrate to the SiC wafer surface, inducing an anodic oxidation reaction to form an oxide layer; while the photogenerated electrons migrate to the surface of the counter electrode (such as a platinum wire) to participate in the hydrogen evolution reaction. The formed oxide layer continuously dissolves in the alkaline electrolyte, gradually evolving into a porous structure on the SiC wafer surface. The etching depth and pore structure of this process can be precisely controlled by adjusting the voltage, alkaline electrolyte concentration, light intensity, and reaction time.

[0037] The light source used in the photoelectrochemical etching stage of this invention can be adjusted according to specific application requirements. The light source type can be a broadband white light source, such as a sunlight irradiation simulation system, or a full-spectrum light source with filtering processing (such as an ultraviolet filter, a bandpass filter in any band within the 300-600 nm range), or a mercury lamp, or an ultraviolet / visible LED module (such as an LED with any single or multiple band combinations within the 190-600 nm ultraviolet / visible light range). The specific wavelength of the light source can be selected based on the bandgap and light absorption characteristics of the silicon carbide material (such as 3C-SiC, 4H-SiC, 6H-SiC), with a preferred wavelength range below 500 nm. Irradiation methods can include direct vertical illumination, side illumination, reflective devices, or fiber optic coupling to adapt to different reaction chamber structures.

[0038] In addition to the constant voltage mode, embodiments of the present invention also support electrochemical control modes such as constant current, voltage step, linear voltage scanning, multi-potential step method, or pulsed voltage to meet different etching requirements. Among them, the constant voltage mode is simple to operate and suitable for large-area uniform etching; the constant current mode can maintain a stable etching rate when the concentration of alkaline electrolyte fluctuates or the light intensity changes; the pulsed voltage mode can enhance the etching depth, control precision, and improve the film stripping selectivity through periodic potential changes, and can also realize the preparation of porous SiC films with multiple pore structures; the linear voltage scanning mode helps to explore the electrochemical response behavior of materials under different potentials and optimize the etching window; the multi-potential step method can set multiple polarization potential points with indefinite time. Polarization starts from the "initial potential" and maintains the potential unchanged for the corresponding holding time before setting the preset polarization potential and time to the "termination potential". In this way, multilayer structures with different pore sizes can be designed for porous silicon carbide films.

[0039] Furthermore, various electrochemical control modes can be synergistically modulated by combining continuous or pulsed voltage or illumination conditions, thereby improving the uniformity of the oxide layer and the controllability of the pore structure. The compatibility of these multiple electrochemical control modes makes this invention highly adaptable and scalable in practical applications. During the subsequent peeling of the porous silicon carbide film, short-duration high-voltage pulses or step voltages can be used to rapidly induce enhanced electric fields and localized stress concentration within the porous silicon carbide film, thus achieving separation between the film and the substrate. This process avoids reliance on mechanical force or complex transfer steps, offering advantages such as fast peeling speed and high film structural integrity. By adjusting parameters such as pulse voltage amplitude, duration, and pulse period, the uniformity of the peeling interface and the repeatability of the process can be further controlled. This electric field-driven peeling mechanism avoids material damage caused by traditional chemical corrosion or mechanical peeling, making it particularly suitable for the fabrication of flexible or transferable porous silicon carbide films, contributing to improved reliability and controllability of the entire process.

[0040] In one embodiment, step four specifically includes: after the flexible porous silicon carbide film has grown to the target thickness, a high voltage (e.g., 15-40 V) is rapidly applied for several seconds to several minutes, such as 3 seconds to 2 minutes. At this time, a significant interface difference is formed between the flexible porous silicon carbide film and the unetched area, and the pore walls become thinner and structurally fragile. Simultaneously, a localized and intense reaction occurs at the interface under the induction of high voltage, accompanied by the rapid generation and release of bubbles, thereby enabling the entire flexible porous silicon carbide film to spontaneously peel off without mechanical intervention, ultimately floating to the surface of the alkaline electrolyte.

[0041] In one embodiment, step four further includes: after the flexible porous silicon carbide film is peeled off, the SiC sheet and the floating flexible porous silicon carbide film are taken out from the alkaline electrolyte and thoroughly rinsed with deionized water to remove residual alkaline electrolyte and by-products; then placed in an oven or in an inert gas environment to dry, thereby obtaining a porous silicon carbide film with complete structure, good flexibility and controllable thickness.

[0042] The method used in the preliminary preparation of porous silicon carbide thin films in this invention is photoelectrochemical etching. Photoelectrochemical technology, through the synergistic effect of applied bias voltage and illumination, significantly improves the separation efficiency of photogenerated carriers and the interfacial reaction activity, which helps to form a flexible porous silicon carbide thin film with a uniform structure. Since it relies solely on an electric field to drive the reaction, the voltage application method is simpler and the equipment requirements are lower, making it suitable for constructing high-efficiency pore structures under certain process conditions.

[0043] The main improvements of the embodiments of the present invention include the following aspects: (1) A two-stage electrochemical scheme for preparing flexible porous silicon carbide films by using white light, ultraviolet light or multi-band light irradiation and then applying high voltage to peel off the films.

[0044] In existing technologies, dry etching methods for preparing porous silicon carbide thin films suffer from high costs and complex processes, hindering large-scale application. Traditional mechanical peeling methods, on the other hand, easily cause edge breakage, numerous structural defects, and irreversible damage to the substrate, making it difficult to achieve large-area, structurally intact film separation. In contrast, this invention utilizes a low-cost electrochemical or photoelectrochemical method to first achieve controllable oxidation and dissolution of the SiC wafer surface under low voltage and illumination conditions, forming a flexible porous silicon carbide thin film. After completing the flexible porous silicon carbide thin film preparation under low voltage and illumination, a high voltage is applied to weaken the interpore connections and promote vigorous reactions. Under the influence of numerous bubbles, the flexible porous silicon carbide thin film is rapidly and completely peeled off.

[0045] (2) Achieving complete transfer of flexible porous silicon carbide thin films Existing silicon carbide thin film peeling technologies suffer from problems such as high structural rigidity, brittleness, and easy breakage, making it difficult to meet the material flexibility requirements of flexible optoelectronic devices, heterogeneous integration, or transferable applications. This invention constructs a highly uniform porous structure through photoelectrochemical processes. This porous structure not only effectively releases internal stress but also maintains structural integrity. The resulting porous silicon carbide thin film possesses excellent flexibility, structural integrity, and mechanical stability, and can be directly used for the fabrication of flexible optoelectronic devices and heterogeneous integration after peeling. This technology overcomes the limitations of traditional methods in balancing structural integrity and flexibility, providing an ideal semiconductor material for flexible optoelectronic devices and heterogeneous integration systems, demonstrating broad application prospects and industrialization potential.

[0046] (3) Optimization of alkaline electrolyte Hydrofluoric acid (HF) is commonly used as the electrolyte in existing electrochemical etching technologies. HF is a highly corrosive and biotoxic chemical that can rapidly penetrate the skin, causing deep tissue burns. Furthermore, the released fluoride ions can combine with calcium and magnesium ions in the body, leading to hypocalcemia, cardiac arrhythmias, and even cardiac arrest, posing significant delayed and potentially fatal risks. In addition, the volatility of HF poses inhalation hazards, potentially causing respiratory burns and even pulmonary edema. Besides the risks during use, the hazards of HF wastewater treatment cannot be ignored: HF wastewater is highly acidic and extremely toxic; improper handling can cause long-term harm to laboratory personnel and the environment, potentially corroding drainage systems and causing fluoride pollution of water bodies. This invention uses a relatively mild alkaline electrolyte to replace traditional HF, ensuring photoelectrochemical etching and thin film stripping of silicon carbide while avoiding process safety and environmental issues. This alkaline electrolyte offers high operational safety and environmental friendliness, and wastewater treatment is simpler and safer, reducing potential harm to the health of laboratory personnel and the environment. This alkaline electrolyte balances reaction efficiency with process safety and environmental friendliness, providing a new solution for the green preparation of flexible porous silicon carbide films.

[0047] (4) Introduction of reaction-assisted technology: The porous silicon carbide film preparation and exfoliation process of the present invention can be carried out under normal pressure, room temperature or temperature control conditions. In order to further improve the stability of the reaction, the uniformity of pore structure distribution and the controllability and integrity of the exfoliation process, a magnetic stirring or ultrasonic-assisted system can be introduced to enhance the local fluidity of the alkaline electrolyte, promote the diffusion of reactants and the timely discharge of reaction products, and avoid phenomena such as reaction stagnation, bubble shielding or local over-etching during the etching process, which helps to obtain porous silicon carbide films with complete structure and high exfoliation interface quality.

[0048] (5) Device Structure Optimization: The present invention can optimize the structure of the implementation device to further improve reaction efficiency and etching uniformity. For example, a more compact, better-sealed, and automated controllable reaction chamber structure can be designed, making it easier to precisely control parameters such as temperature, fluid, and electric field. It can also integrate multi-functional modules such as sample introduction, cleaning, and stripping to achieve continuous or semi-automated operation. In addition, by changing the incident angle, illumination direction, or light source arrangement of white light and ultraviolet light sources, the illumination distribution on the sample surface can be optimized to improve the excitation and separation efficiency of photogenerated carriers, thereby improving the uniformity of pore structure distribution and the controllability of the stripping process.

[0049] The implementation apparatus of this invention can be expanded from a simple electrochemical reaction cell to an automated modular system. This system can integrate a light source, an electrode module, a temperature control module, and a gas-liquid flow channel, and can be equipped with a thin film collection device to support automated operation processes from etching, stripping to transfer, significantly improving the production efficiency of large-area flexible porous SiC thin films.

[0050] The embodiments of the present invention can also be optimized in the following ways: (1) Accelerate the porous reaction rate by combining with additives such as sacrificial agents and strong oxidants: In this embodiment of the invention, electron sacrificial agents (such as periodate, ferric salts, etc.) can be added to the alkaline electrolyte to reduce the recombination of photogenerated electron-hole pairs on the silicon carbide surface and improve the oxidation and etching behavior of photogenerated electrons and holes on silicon carbide; strong oxidizing agents (such as potassium permanganate, sodium persulfate, etc.) can also be added to provide stronger oxidizing power to oxidize the new active interfaces generated during the etching process and accelerate the oxidation and dissolution of the surface during the reaction.

[0051] (2) Compatibility with other wide bandgap materials: Besides silicon carbide, this photoelectrochemical approach to fabricating porous structures and high-voltage stripping holds promise for application to other wide-bandgap semiconductor materials such as gallium nitride and gallium oxide. These materials also present a need for thin-film transfer or stress relief in optoelectronic devices, microwave devices, and high-frequency power devices. Preliminary experiments by the inventors indicate that a similar principle is feasible in gallium nitride.

[0052] (3) Porous structure regulation and functional expansion: By further controlling the reaction conditions (such as wavelength selection, type of alkaline electrolyte, applied voltage, cation regulation, etc.), it is possible to construct different pore shapes, gradient pore sizes, and multilayer porous structures, providing product services for subsequent applications in flexible electronics and wearable devices, sensors, photocatalysis, and supercapacitors.

[0053] The present invention will be further described below through specific embodiments.

[0054] Example 1 This embodiment describes a method for preparing and peeling a flexible porous silicon carbide thin film, combined with... Figure 1 As shown, the specific steps are as follows: (1) Silicon carbide pretreatment: The purchased commercial conductive SiC wafers were cleaned by sequentially ultrasonicating with 50 mL acetone, 50 mL ethanol, and 50 mL deionized water for 10 min to remove any adsorbed dust and residual contaminants on the surface. Immediately after cleaning, the SiC wafers were purged with a dry nitrogen stream for 30 s to remove any residual moisture on the surface.

[0055] (2) Preparation of alkaline electrolyte: Add deionized water to 5.61 g of potassium hydroxide solid and bring the volume to 100 mL. After the solid is completely dissolved, a 1 mol·L⁻¹ electrolyte is obtained. -1 A potassium hydroxide solution.

[0056] (3) Electrode system construction: A metal sheet was attached to the back of the SiC sheet using copper tape as a conductive layer. The conductive layer was insulated and protected against leakage by a strong acid and alkali resistant silicone pad. A three-electrode electrochemical system was established with the SiC sheet as the working electrode, the Pt electrode as the counter electrode, and mercury / mercury oxide as the reference electrode.

[0057] (4) Preparation of porous silicon carbide thin film: Add 10 mL of potassium hydroxide solution to the system in step (3). Then, at room temperature, use a xenon lamp as the light source. The light spot emitted from the xenon lamp light source is perpendicularly irradiated onto the surface of the working electrode after passing through a total reflection sheet. The height of the light source from the surface of the etching solution is 8 cm. The light source passes through an AM1.5G filter to adjust the wavelength-energy distribution of the light source to be close to that of sunlight. Adjust the current to around 18.0 A to achieve a light power density of 600 mW·cm. -2 Subsequently, a voltage was applied to the SiC wafer, with the potential set to 10V (relative to the reference electrode), and a long etching process was performed for 120 minutes to obtain a porous silicon carbide film.

[0058] (5) Film peeling: Turn off the light source and apply a high voltage of 35V to the silicon carbide for 3 seconds. The instantaneous high voltage will break the connection between the film and the substrate and cause peeling. Then, use flexible silicone to adsorb and transfer the film and wash it with deionized water.

[0059] Example 2 The method for preparing and peeling a flexible porous silicon carbide thin film according to this embodiment includes the following specific steps: (1) Silicon carbide pretreatment: The purchased commercial conductive SiC wafers were cut into 1cm*1cm square pieces and cleaned. The wafers were then subjected to ultrasonic treatment for 10 minutes using 25mL acetone, 25mL ethanol, and 50mL deionized water to remove any adsorbed dust and residual contaminants on the surface. Immediately after cleaning, the SiC wafers were purged with a dry nitrogen stream for 30 seconds to remove any residual moisture on the surface.

[0060] (2) Preparation of alkaline electrolyte: Add deionized water to 5.61 g of potassium hydroxide solid and bring the volume to 100 mL. After the solid is completely dissolved, 1 mol L⁻¹ is obtained. -1 A potassium hydroxide solution.

[0061] (3) Electrode system construction: A metal sheet was attached to the back of the SiC sheet using copper tape as a conductive layer. The conductive layer was insulated and protected against leakage by a strong acid and alkali resistant silicone pad. A three-electrode electrochemical system was established with SiC as the working electrode, Pt as the counter electrode, and mercury / mercury oxide as the reference electrode.

[0062] (4) Preparation of porous silicon carbide thin film: Add 15 mL of potassium hydroxide solution to the system in step (3). Then, at room temperature, use a xenon lamp as the light source. The light spot emitted from the xenon lamp light source is perpendicularly irradiated onto the surface of the working electrode after passing through a total reflection sheet. The height of the light source from the surface of the etching solution is 10 cm. The light source passes through an AM1.5G filter to adjust the wavelength-energy distribution of the light source to be close to that of sunlight. Adjust the current to around 15.0 A to achieve a light power density of 400 mW·cm. -2 Subsequently, a voltage was applied to the SiC wafer, with the potential set to 8V (relative to the reference electrode), and a long etching process was performed for 120 minutes to obtain a porous silicon carbide film.

[0063] (5) Film peeling: Turn off the light source and apply a 25V high voltage to the silicon carbide for 20 seconds. The instantaneous high voltage will break the connection between the film and the substrate and cause peeling. Then, use flexible silicone to adsorb and transfer the film and wash it with deionized water.

[0064] Example 3 The method for preparing and peeling a flexible porous silicon carbide thin film according to this embodiment includes the following specific steps: (1) Silicon carbide pretreatment: The purchased commercial conductive SiC wafers were cut into 2.5cm*2.5cm square pieces and cleaned. The wafers were then subjected to ultrasonic treatment for 10 minutes using 50mL acetone, 50mL ethanol, and 50mL deionized water to remove any adsorbed dust and residual contaminants. Immediately after cleaning, the SiC wafers were purged with a dry nitrogen stream for 30 seconds to remove any residual moisture.

[0065] (2) Preparation of alkaline electrolyte: Add deionized water to 2.81 g of potassium hydroxide solid and bring the volume to 100 mL. After the solid is completely dissolved, 0.5 mol L⁻¹ is obtained. -1 A potassium hydroxide solution.

[0066] (3) Electrode system construction: A metal sheet was attached to the back of the SiC sheet using copper tape as a conductive layer. The conductive layer was insulated and protected against leakage by a strong acid and alkali resistant silicone pad. A three-electrode electrochemical system was established with SiC as the working electrode, Pt as the counter electrode, and mercury / mercury oxide as the reference electrode.

[0067] (4) Preparation of porous silicon carbide thin film: Add 20 mL of potassium hydroxide solution to the system in step (3). Then, at room temperature, use a xenon lamp as the light source. The light spot emitted from the xenon lamp light source is perpendicularly irradiated onto the surface of the working electrode after passing through a total reflection sheet. The height of the light source from the surface of the etching solution is 10 cm. The light source passes through an AM1.5G filter to adjust the wavelength-energy distribution of the light source to be close to that of sunlight. Adjust the current to around 15.0 A to achieve a light power density of 400 mW·cm. -2 Subsequently, a voltage was applied to the SiC wafer, with the potential set to 6V (relative to the reference electrode), and a long etching process was performed for 180 minutes to obtain a porous silicon carbide film.

[0068] (5) Film peeling: Turn off the light source and apply a high voltage of 15V to the silicon carbide for 30 seconds. The large number of bubbles generated by the high voltage will destroy the connection between the film and the substrate and cause peeling. Then, use flexible silicone to adsorb and transfer the film and wash it with deionized water.

[0069] Example 4 The method for preparing and peeling a flexible porous silicon carbide thin film according to this embodiment includes the following specific steps: (1) Silicon carbide pretreatment: The purchased commercial conductive SiC wafers were cut into 1.2cm*1.2cm square pieces and cleaned. The wafers were then subjected to ultrasonic treatment for 10 minutes using 20mL acetone, 20mL ethanol, and 50mL deionized water to remove any adsorbed dust and residual contaminants. Immediately after cleaning, the SiC wafers were purged with a dry nitrogen stream for 30 seconds to remove any residual moisture.

[0070] (2) Preparation of alkaline electrolyte: Add deionized water to 11.2 g of potassium hydroxide solid and bring the volume to 100 mL. After the solid is completely dissolved, 2 mol L⁻¹ is obtained. -1 A potassium hydroxide solution.

[0071] (3) Electrode system construction: A metal sheet was attached to the back of the SiC sheet using copper tape as a conductive layer. The conductive layer was insulated and protected against leakage by a strong acid and alkali resistant silicone pad. A three-electrode electrochemical system was established with SiC as the working electrode, Pt as the counter electrode, and mercury / mercury oxide as the reference electrode.

[0072] (4) Preparation of porous silicon carbide thin film: Add 6 mL of potassium hydroxide solution to the system in step (3). Then, at room temperature, use a xenon lamp as the light source. The light spot emitted from the xenon lamp light source is perpendicularly irradiated onto the surface of the working electrode after passing through a total reflection sheet. The height of the light source from the surface of the etching solution is 10 cm. The light source passes through an AM1.5G filter to adjust the wavelength-energy distribution of the light source to be close to that of sunlight. Adjust the current to around 15.0 A to achieve a light power density of 600 mW·cm. -2 Subsequently, a voltage was applied to the SiC wafer, with the potential set to 4V (relative to the reference electrode), and a long etching process was performed for 240 minutes to obtain a porous silicon carbide film.

[0073] (5) Film peeling: Turn off the light source and apply a high voltage of 20V to the silicon carbide for 15 seconds. The large number of bubbles generated by the high voltage will destroy the connection between the film and the substrate and cause peeling. Then, use flexible silicone to adsorb and transfer the film and wash it with deionized water.

[0074] Example 5 The method for preparing and peeling a flexible porous silicon carbide thin film according to this embodiment includes the following specific steps: (1) Silicon carbide pretreatment: The purchased commercial conductive SiC wafers were cut into 1.5cm*1.5cm square pieces and cleaned. The wafers were then subjected to ultrasonic treatment for 10 minutes using 20mL acetone, 20mL ethanol, and 50mL deionized water to remove any adsorbed dust and residual contaminants. Immediately after cleaning, the SiC wafers were purged with a dry nitrogen stream for 30 seconds to remove any residual moisture.

[0075] (2) Preparation of alkaline electrolyte: Add deionized water to 2.39 g of lithium hydroxide solid and bring the volume to 100 mL. After the solid is completely dissolved, 1 mol L⁻¹ is obtained. -1 Lithium hydroxide solution.

[0076] (3) Electrode system construction: Silver paste was used to attach silver tape to the back of the SiC wafer as a conductive layer, and a strong acid and alkali resistant silicone pad was used to insulate and protect the conductive layer from water leakage. A two-electrode electrochemical system was established with SiC as the working electrode and Pt wafer as the counter electrode.

[0077] (4) Preparation of porous silicon carbide thin film: Add 15 mL of potassium hydroxide solution to the system in step (3). Then, at room temperature, use a 340 nm ultraviolet LED lamp as the light source. The light spot emitted by the LED lamp is perpendicularly irradiated onto the surface of the working electrode. The height of the light source from the surface of the etching solution is 6 cm. The light source is unfiltered, and the light power density is adjusted to reach 100 mW·cm. -2 Subsequently, a voltage of 19V was applied to the SiC wafer, and a long etching process was performed for 120 minutes to obtain a porous silicon carbide film.

[0078] (5) Film peeling: Turn off the light source and apply a high voltage of 25V to the silicon carbide for 15 seconds. The large number of bubbles generated by the high voltage will destroy the connection between the film and the substrate and cause peeling. Then, use flexible silicone to adsorb and transfer the film and wash it with deionized water.

[0079] The porous silicon carbide films prepared in Examples 1-5 above exhibit abundant porous structures on their surface, with microstructures as follows: Figures 2-6 As shown, higher voltage produces more and denser pores. Surface Raman spectroscopy of the resulting porous silicon carbide film was performed, as shown... Figure 7 As shown, these films all maintain Raman signals consistent with the silicon carbide wafer itself. Characteristic Raman vibration modes of silicon carbide include: the E2 longitudinal acoustic mode (LA, 197 cm⁻¹). -1 E2 transverse acoustic mode (TA, 204 cm) -1 E1 transverse acoustic mode (TA, 266 cm) -1 A1 longitudinal acoustic mode (LA, 610 cm) -1 E2 transverse optical mode (TO, 777 cm) -1 E1 transverse optical mode (TO, 799 cm) -1 ) and A1 transverse optical mode (LO, 976 cm) -1 ), of which 204cm -1Nearby characteristic optical planar mode (FTA) confirms that these SiC crystals are all 4H-SiC. The porous silicon carbide films also retain the same peaks as the original SiC wafers. Compared to the original 4H-SiC, the Al(LO) peak of the porous SiC films shows significant broadening and redshift, while the Al(LO) phonon line shape and peak shift are strongly dependent on the carrier concentration within the 4H-SiC, indicating that the porous silicon carbide films exhibit a higher carrier concentration. Simultaneously, they exhibit good flexibility and bendability. Figure 8 This has broadened the application fields of silicon carbide thin film materials.

[0080] The flexible porous silicon carbide thin film from Example 1 is applied to ultraviolet light detection, such as... Figure 9 As shown, at 0.5 mol L -1 Accepts 20 mW·cm in sulfuric acid aqueous solution -2 Under 340 nm LED illumination, it exhibited a wavelength of 8 μA·cm⁻¹. -2 The response current is compared to 0.15 μA·cm under 465nm LED illumination. -2 The response current was more pronounced, indicating that the material exhibits high selectivity for ultraviolet light and shows great potential in solar-blind detectors and photoelectrochemical cells for photodetection. Simultaneously, the porous structure endows it with excellent adsorption properties, making it a potential material for dye adsorption. 2 mg of a flexible porous silicon carbide film was placed in an atmosphere containing 100 mmol L... -1 When methylene blue (MB) aqueous solution is allowed to stand, it can be observed that the concentration of methylene blue in the solution continuously decreases with increasing time, as shown in the following results. Figure 10 As shown above, the porous structure of the flexible porous silicon carbide film is beneficial for its adsorption of dyes.

[0081] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A method for preparing and peeling a flexible porous silicon carbide thin film, characterized in that, include: Step 1: Pre-process the SiC wafer; Step 2: Construct an electrode system, which includes a working electrode and a counter electrode. The working electrode is the pretreated SiC sheet. Place the electrode system in an alkaline electrolyte and connect the electrode system to an electrochemical workstation. Step 3: Apply an electric field to the SiC wafer using the electrochemical workstation, and simultaneously illuminate the surface of the SiC wafer to form a flexible porous silicon carbide thin film on the surface of the SiC wafer; Step 4: Apply a high voltage to peel off the flexible porous silicon carbide film.

2. The method for preparing and peeling off a flexible porous silicon carbide thin film according to claim 1, characterized in that, Step one specifically includes: ultrasonically cleaning the SiC wafer sequentially in acetone, anhydrous ethanol, and deionized water, each step lasting 5-10 minutes; after the ultrasonic cleaning is completed, the SiC wafer is placed in a dry nitrogen stream to dry.

3. The method for preparing and peeling off a flexible porous silicon carbide thin film according to claim 1, characterized in that, In step two, the alkaline electrolyte is prepared by dissolving an alkaline electrolyte in water. The alkaline electrolyte is at least one selected from potassium hydroxide, cesium hydroxide, rubidium hydroxide, sodium hydroxide, and lithium hydroxide. The concentration of the alkaline electrolyte is 0.01-3 mol / L. -1 .

4. The method for preparing and peeling off a flexible porous silicon carbide thin film according to claim 1 or 3, characterized in that, In step two, hydrofluoric acid, ammonium fluoride, or sodium fluoride are added to the alkaline electrolyte.

5. The method for preparing and peeling off a flexible porous silicon carbide thin film according to claim 1, characterized in that, In step two, the electrode system further includes a reference electrode, the counter electrode is a platinum wire, and the reference electrode is a standard mercury oxide electrode.

6. The method for preparing and peeling off a flexible porous silicon carbide thin film according to claim 1, characterized in that, In step three, the electrochemical control mode of the electrochemical workstation is constant current, voltage step, linear voltage scan, multi-potential step method, or pulse voltage.

7. The method for preparing and peeling off a flexible porous silicon carbide thin film according to claim 1, characterized in that, In step three, the surface of the SiC wafer is illuminated with white light or ultraviolet light, wherein the intensity of the white light is 300~1000 mW cm⁻¹. -2 The intensity of ultraviolet light is 50~500 mW cm⁻¹ -2 .

8. The method for preparing and peeling off a flexible porous silicon carbide thin film according to claim 1, characterized in that, In step three, a constant low voltage of 4-10 V is applied to the SiC wafer through the electrochemical workstation.

9. The method for preparing and peeling off a flexible porous silicon carbide thin film according to claim 1, characterized in that, In step four, the high voltage is 15-40 V and lasts for several seconds to several minutes.

10. The method for preparing and peeling off a flexible porous silicon carbide thin film according to claim 1, characterized in that, Step four further includes: after the flexible porous silicon carbide film is peeled off, the flexible porous silicon carbide film is taken out from the alkaline electrolyte, rinsed with deionized water, and then dried to obtain the flexible porous silicon carbide film.

Images