A patterned 4H-SiC nanorod array thin film, a preparation method thereof, and a photoelectric detection device

Abstract

The present invention provides a patterned 4H-SiC nanowire array thin film, a preparation method thereof, and a photoelectric detection device. The 4H-SiC wafer is subjected to p-type doping and dry oxidation to obtain a 4H-SiC wafer covered with an oxide layer; a polystyrene microsphere solution is spin-coated on the 4H-SiC wafer covered with the oxide layer, and heated to shrink the polystyrene microspheres and self-assemble them to form a monolayer film, and gold is deposited by evaporation. The polystyrene microspheres are removed to obtain a 4H-SiC wafer with a gold nanopattern; it is contacted with a copper plate as an anode, and an external pulsed current is applied in a three-electrode system to etch the 4H-SiC wafer with the gold nanopattern to form a patterned 4H-SiC nanowire array thin film on the wafer, and the patterned 4H-SiC nanowire array thin film is peeled off. The present invention prepares an ordered and patterned nanowire array thin film with few defects and high resolution after patterning.

Description

Technical Field

[0001] The present invention belongs to the technical field of the preparation of optoelectronic detection devices. Specifically, it relates to a patterned 4H-SiC nanoarray thin film, a preparation method thereof, and an optoelectronic detection device. Background Art

[0002] With the continuous in-depth research and exploration work in the fields of astronomy, high-energy physics, space technology, etc. in recent years, and the rapid expansion of application prospects in cosmic exploration, artificial satellites, etc., patterned metal and metal oxide nanostructured materials with semiconductor, light, electricity, magnetism and other properties have broad application prospects in the fields of solar cells, sensors, nanogenerators, etc. due to their unique properties. They are the mainstream development direction of the miniaturization, intelligence and high speed of microelectronic components and have become one of the research hotspots in the current frontier fields. Since patterned nanostructured materials, especially patterned nanowire arrays, exhibit different properties according to the differences in their types, sizes, morphologies, spatial positions and densities, the research on the preparation and application of patterned nanowire arrays with controllable sizes, positions, densities and growth orientations has very important theoretical significance and broad application prospects. In recent years, with the rise of nanoscience and technology, low-dimensional SiC nanostructures have attracted wide attention. Low-dimensional SiC nanostructures have excellent physical and chemical properties, such as high band gap, high critical breakdown electric field, high thermal conductivity, electron saturation mobility, small dielectric constant, good chemical stability, and at the same time have high hardness, wear resistance, low thermal expansion coefficient and good mechanical properties, etc., enabling them to maintain a relatively stable working state under extreme environments. SiC is currently the most promising third-generation semiconductor material, and its greatest advantage can be summarized as having a large energy band gap, high thermal conductivity and large electron saturation drift rate, making it favored in the field of ultraviolet detection and very suitable for the preparation of high-density integrated ultraviolet optoelectronic detection devices, and the main detection targets are ultraviolet and near-ultraviolet light.

[0003] The synthesis of SiC low-dimensional nanomaterials is the basis for their practical applications. However, most of the existing preparation methods of SiC low-dimensional materials currently involve high-temperature (generally greater than or equal to 1000 °C) and high-pressure environments, resulting in problems such as complex processes, high equipment requirements, difficult control of the morphology of SiC nanomaterials, and poor process repeatability and stability. Therefore, exploring the controllable preparation of patterned low-dimensional SiC materials with good morphology under low-cost conditions has good practical significance and development prospects.

[0004] There are many methods for preparing SiC nanowires, which can be divided into two categories, namely, the "bottom-up" growth method and the "top-down" etching method. The "bottom-up" growth method refers to building the required nanostructures from individual atoms and molecules. For semiconductor nanowires, the preparation methods include the vapor-liquid-solid (VLS) method, chemical vapor deposition (CVD), solid-liquid-solid method, laser ablation method, nanoporous template method, arc discharge method, and many thermal reduction methods. The nanowires prepared by these methods are generally cubic in structure, prone to generating more defects, with a small amount of products, contamination by metal catalyst particles, high costs, and a long synthesis time. The "top-down" etching methods include dry etching and wet etching. There have been many reports on dry etching. During preparation, damage and small cones are likely to occur, and it is not easy to control. The prepared size is relatively large, which is not suitable for the preparation of one-dimensional nanomaterial devices. Summary of the Invention

[0005] In view of the above problems, the present invention provides a patterned 4H-SiC nanoarray thin film, a preparation method thereof, and a photoelectric detection device. An ordered and patterned nanowire array thin film with few defects can be prepared through a relatively simple process flow. After patterning, it has a high resolution (feature size and pitch < 50 nm), the shape and pitch are controllable, and it is applied to photodetector materials.

[0006] The present invention is realized through the following technical solutions:

[0007] A preparation method of a patterned 4H-SiC nanoarray thin film, the method comprising the following steps:

[0008] First, an N-type 4H-SiC wafer with a thickness of 350 ± 25 μm and a crystal phase of <1120> is cut into rectangular or circular SiC wafers, and then cleaned, soaked, and dried;

[0009] After the cleaned SiC wafer is mixed evenly with a p-type doping source, it is loaded into a quartz tube and sealed. The pressure inside the sealed quartz tube is 1 mTorr. The sealed quartz tube is placed in a muffle furnace and heated at a heating rate of 3 - 10 °C / min, the heating temperature is 1000 - 1200 °C, and the holding time is 60 - 600 min. After the heating is completed, the sample is naturally cooled to room temperature in the furnace and then taken out to obtain a doped SiC wafer;

[0010] The doped SiC wafer is subjected to dry oxidation in an air atmosphere at 1000 - 1100 °C for 15 - 40 min to obtain an oxide layer of about 200 nm on the SiC wafer, and a SiC wafer covered with an oxide layer is obtained;

[0011] Polystyrene (PS) microspheres with a diameter of about 100 nm were spin-coated on a SiC wafer covered with an oxide layer and heated to 250 °C on a graphite hot plate and kept for 15 min to reduce the polystyrene (PS) microspheres to about 60 nm. At this time, the spacing between the polystyrene (PS) microspheres was about 80 nm, and they adhered more firmly, self-assembling into a monolayer film. Then, about 100 nm thick Au nanoparticles were deposited on the surface by electron beam evaporation. Finally, the PS microspheres were removed by ultrasonic treatment in absolute ethanol, and a SiC wafer with a honeycomb gold nanopattern was obtained and used as a catalyst template;

[0012] During the electrochemical etching process, the SiC wafer with a honeycomb gold nanopattern and the graphite sheet were used as the anode and cathode respectively. In an etching solution composed of HF, C2H5OH, and H2O2, a pulsed current was applied to etch the SiC wafer with a honeycomb gold nanopattern at room temperature; Subsequently, the 4H-SiC nanowire array film was peeled off; Finally, the obtained 4H-SiC nanowire array film was washed with ethanol and deionized water respectively, and dried to obtain the 4H-SiC nanowire array film.

[0013] A preparation method of a photodetector based on the 4H-SiC nanorod array film. The cleaned interdigital electrodes (electrode spacing 200 μm) were polished with sandpaper, and the annealed 4H-SiC nanorod array film was transferred onto the interdigital electrodes, and then pressed to improve the contact between the material and the electrodes; If there are no interdigital electrodes, nickel electrodes with a spacing of 40 μm can be evaporated by electron beam evaporation, and then the above operations are repeated. Finally, rapid annealing was carried out in a vacuum annealing furnace, and the photodetector based on the 4H-SiC nanorod array film was prepared.

[0014] Preferably, the 4H-SiC wafer is industrial grade. That is, the cumulative length of scratches on the surface of the 4H-SiC wafer < 1 diameter, and the number ≤ 3, and the microtube density ≤ 1 per cm 2 .

[0015] Preferably, the cleaning is as follows: The 4H-SiC wafer was ultrasonically cleaned in acetone and deionized water for 10 min in sequence.

[0016] Preferably, the immersion is carried out in a mixed solution of hydrofluoric acid and ethanol for 120 s, where the volume ratio of hydrofluoric acid to ethanol is 0.8 - 1.2:1. Selecting appropriate cleaning reagents and appropriate immersion time can fully clean the silicon carbide wafer and avoid mixing in impurities.

[0017] Preferably, the drying is to place the 4H-SiC wafer in an oven at 35 - 45 °C for 8 - 12 min.

[0018] Preferably, the p-type doping source during doping is ammonium chloride or aluminum chloride with a purity of 99.99%.

[0019] Preferably, the spin-coated polystyrene (PS) microspheres are spin-coated using a spin coater at 2000 rpm for 1 - 3 min.

[0020] Preferably, in the composition of the etching solution, the volume ratio of hydrofluoric acid, ethanol, and hydrogen peroxide is 2.5 - 3.5:6:1. More preferably, in the etching solution, the volume ratio of hydrofluoric acid, ethanol, and hydrogen peroxide is 3:6:1.

[0021] Preferably, the time for the etching treatment is 15 - 25 min, and the time for the stripping treatment is 20 - 40 s.

[0022] Preferably, the current density used for the etching treatment is 100 - 140 mA / cm 2 , the cycle time is 0.8 ms, and the pause time is 0.4 ms. During the etching process, the morphology of the 4H-SiC wafer can be regulated by controlling factors such as the etching time and current magnitude, and it can be monitored by SEM technology. Finally, a 4H-SiC nanoarray film with the desired morphology can be accurately obtained.

[0023] Preferably, the method for the stripping treatment is the DC stripping method, that is, a DC current is applied to strip the 4H-SiC nanoarray film.

[0024] Preferably, the morphology of the 4H-SiC nanoarray film is long nanowires, and the diameter of the long nanowires is 30 - 45 nm.

[0025] Preferably, the annealing treatment of the 4H-SiC nanoarray film is as follows: annealing is carried out at 1000 °C, and the program settings are: heating from room temperature to 200 °C in 10 min, heating to 980 °C in 20 min, heating to 1000 °C in 10 min, holding for 60 min, and then naturally cooling to room temperature. When fabricating a photodetector device based on this 4H-SiC nanoarray film, the acting force and temperature during cold pressing should be strictly controlled. Press at 50 N for 5 min at 300 °C, and then press at 50 N for 3 h at 200 °C. If the pressure is too large, cracks or even fractures will occur in the device, and if it is too small, the performance requirements cannot be met; if the temperature is too high, the device will conduct.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The present invention adopts a chemical etching method with an externally applied pulsed current. This method reduces the size of the dimension through selective etching and prepares 4H-SiC nanowires by regulating the pulsed current. Compared with the traditional chemical etching method without current or with a direct current applied, the nanowires prepared by the present invention have fewer defects and have the advantages of being simple, batchable, and low-cost. Different from the single-morphology 4H-SiC nanoarray prepared by the traditional method, the method for preparing the SiC nanoarray thin film of the present invention has a simple process method, good repeatability, and a simple peeling method. The peeled SiC nanoarray thin film is complete and has a high success rate, which lays a good foundation for the large-scale preparation of ordered and oriented SiC nanopore arrays and their applications using a large wafer substrate as a raw material.

[0028] Furthermore, the anodic oxidation etching process of the present invention can better control the morphological changes of the 4H-SiC nanoarray by regulating the etching process parameters, and can transition from nanopores to nanowires and then to a disordered porous morphology. Moreover, the length of the nanowires can be regulated by the etching time. However, the present invention needs to select a 4H-SiC nanoarray with a longer nanowire morphology as a product for practical applications, and both the short nanowire morphology and the disordered porous morphology will cause a decline in the performance during the product application process.

[0029] In the patterned 4H-SiC nanowire array thin film of the present invention, the array is a vertical nanowire array. Compared with the thin film or planar disordered nanowires, the vertical nanowire array structure shows more excellent light absorption ability, higher carrier generation, and higher recovery efficiency, which benefits from the high surface-volume ratio, surface carrier recombination, and effective optical coupling. It can be applied to photodetectors and has a fast response to ultraviolet light of 365 nm, with a response time of 0.25 s, showing high potential in the field of ultraviolet detection. Brief Description of the Drawings

[0030] Figure 1 It is the microscopic morphology of the 4H-SiC nanoarray thin film prepared in Example 1 of the present invention.

[0031] Figure 2 It is the IT curve graph of the ultraviolet detector based on the patterned 4H-SiC nanoarray prepared in Example 1 of the present invention under a 365 nm excitation light source.

[0032] Figure 3 It is the microscopic morphology of the 4H-SiC nanoarray thin film prepared in Example 2 of the present invention.

[0033] Figure 4 It is the microscopic morphology of the 4H-SiC nanoarray thin film prepared in Example 3 of the present invention. Detailed Description of the Invention

[0034] To further understand the present invention, the present invention will be described below in conjunction with embodiments. These descriptions are only to further explain the features and advantages of the present invention and are not intended to limit the claims of the present invention.

[0035] Example 1

[0036] The industrial-grade 4H-SiC wafers are first cut into 4H-SiC wafers with a size of 0.7×1.5 cm, ultrasonically cleaned in acetone and deionized water for 15 min respectively, then immersed in a mixed solution of hydrofluoric acid and ethanol with a volume ratio of 1:1 for 120 s, and after taking out, the 4H-SiC wafers are placed in an oven at 60 °C and dried for 10 min; 2 After the cleaned 4H-SiC wafers are uniformly mixed with ammonium chloride (p-type doping source) at a mass ratio of 10:1, they are sealed in a quartz tube with a tube length of 15 cm, an inner tube diameter of 1 cm, a tube wall thickness of 2 mm, and a pressure of 1 mTorr after sealing. The sealed quartz tube is placed in a muffle furnace and heated at a heating rate of 10 °C / min, the heating temperature is 1200 °C, and the holding time is 180 min. After the heating is completed, the sample is taken out after natural cooling to room temperature with the furnace;

[0037] The 4H-SiC wafers are subjected to dry oxidation in an air atmosphere at 1100 °C for 40 min to obtain an oxide layer of about 200 nm;

[0038] Polystyrene (PS) microspheres with a diameter of about 100 nm are spin-coated on the 4H-SiC wafers at 2000 rpm for 2 min by using a spin coater, and heated on a graphite hot plate at 250 °C for 15 min, then the PS microspheres are reduced to about 60 nm. At this time, the interval between the PS microspheres is about 80 nm, and they are attached more firmly, self-assembled to form a monolayer film, then gold is evaporated and deposited, and finally the PS microspheres are removed by ultrasonic treatment in absolute ethanol for 20 min, dried, and a honeycomb gold nanopattern is prepared, and it is used as a catalyst template;

[0039] The 4H-SiC wafer with the honeycomb gold nanopattern is placed in a mold as the anode, the C surface (matte surface) of the 4H-SiC wafer is in contact with the copper sheet, the graphite plate is used as the cathode, the wires are connected, and it is immersed in an etching solution mixed with hydrofluoric acid, ethanol, and hydrogen peroxide with a volume ratio of 3:6:1, and etched under a pulsed current with a current density of 100 mA / cm

[0040] The 4H-SiC wafer with the honeycomb gold nanopattern is placed in a mold as the anode, the C surface (matte surface) of the 4H-SiC wafer is in contact with the copper sheet, the graphite plate is used as the cathode, the wires are connected, and it is immersed in an etching solution mixed with hydrofluoric acid, ethanol, and hydrogen peroxide with a volume ratio of 3:6:1, and etched under a pulsed current with a current density of 100 mA / cm 2 for 20 min; wherein, the cycle time is 0.8 ms and the pause time is 0.4 ms;

[0041] Change the pulsed current to direct current, etch for 30 s for stripping, strip the 4H-SiC wafer, take it out and dry it. Use double-sided tape to achieve the stripping of the large-area 4H-SiC nanowire array film from the 4H-SiC wafer substrate, and then remove the double-sided tape with ethanol.

[0042] Transfer the 4H-SiC nanowire array film annealed at 1000 °C for 60 min to the interdigital electrode, then press it at 300 °C with 50 N for 5 min, and then press it at 200 °C with 50 N for 3 h to improve the contact between the material and the electrode. Finally, perform rapid annealing at 1000 °C in a vacuum annealing furnace, and complete the preparation of the photodetector device based on the 4H-SiC nanorarray film and conduct photoelectric performance tests. The microscopic morphology of the 4H-SiC nanorarray film is as shown in the appendix Figure 1 As shown, the 4H-SiC nanorarrays are perpendicular to the film thickness direction, and the array structure is regular. The performance test results of the photodetector device under a 365 nm excitation light source are as shown in Figure 2 As shown, it can be seen that it has a fast response to ultraviolet light at 365 nm, and the response time is 0.25 s.

[0043] Example 2

[0044] Cut the industrial-grade 4H-SiC wafer into 4H-SiC wafers with a size of 0.7×1.5 cm 2 , ultrasonically clean them in acetone and deionized water for 15 min respectively, then immerse them in a mixed solution of hydrofluoric acid and ethanol with a volume ratio of 1:1 for 120 s, and after taking them out, place the 4H-SiC wafers in an oven at 60 °C and dry them for 10 min;

[0045] After mixing the cleaned 4H-SiC wafers and ammonium chloride (p-type doping source) evenly at a mass ratio of 10:1, seal them in a quartz tube with a tube length of 15 cm, an inner tube diameter of 1 cm, a tube wall thickness of 2 mm, and a pressure of 1 mTorr after sealing. Place the sealed quartz tube in a muffle furnace for heating, with a heating rate of 3 °C / min, a heating temperature of 1000 °C, and a holding time of 60 min. After the heating is completed, the sample is taken out after natural cooling to room temperature with the furnace;

[0046] The 4H-SiC wafer is subjected to dry oxidation at 1100 °C for 20 min in an air atmosphere to obtain an oxide layer;

[0047] Spin coat polystyrene (PS) microspheres with a diameter of about 100 nm on a 4H-SiC wafer at 2000 rpm for 2 min using a spin coater. Heat the PS microspheres on a graphite hot plate at 250 °C for 15 min to shrink the PS microspheres to about 60 nm. At this time, the spacing between PS microspheres is about 80 nm, and they are more firmly attached. Self-assemble to form a monolayer film, then evaporate and deposit gold. Finally, ultrasonically clean the PS microspheres in absolute ethanol for 20 min, dry them, and obtain a honeycomb gold nanomaterial pattern, which is used as a catalyst template;

[0048] Place the 4H-SiC wafer with the honeycomb gold nanomaterial pattern into a mold as the anode. The C surface (matte surface) of the 4H-SiC wafer is in contact with the copper sheet. Use a graphite plate as the cathode, connect the wires, and immerse them in an etching solution composed of hydrofluoric acid, ethanol, and hydrogen peroxide with a volume ratio of 2.5:6:1. Etch for 15 min under a pulsed current with a current density of 120 mA / cm 2 where the cycle time is 0.8 ms and the pause time is 0.4 ms;

[0049] Change the pulsed current to a direct current, etch for 30 s for stripping, strip the 4H-SiC wafer, take it out and dry it. Use double-sided tape to achieve the stripping of the large-area 4H-SiC nanowire array film from the 4H-SiC wafer substrate, and then remove the double-sided tape with ethanol.

[0050] Example 3

[0051] First, cut the industrial-grade 4H-SiC wafer into 4H-SiC wafers with a size of 0.7×1.5 cm 2 Ultrasonically clean them in acetone and deionized water for 15 min respectively, then immerse them in a mixed solution of hydrofluoric acid and ethanol with a volume ratio of 1:1 for 120 s. After taking them out, place the 4H-SiC wafers in an oven at 60 °C and dry them for 10 min;

[0052] After mixing the cleaned 4H-SiC wafers and ammonium chloride (p-type doping source) evenly at a mass ratio of 10:1, seal them in a quartz tube with a tube length of 15 cm, an inner tube diameter of 1 cm, a tube wall thickness of 2 mm, and a pressure of 1 mTorr after sealing. Place the sealed quartz tube in a muffle furnace and heat it at a heating rate of 10 °C / min, a heating temperature of 1100 °C, and a holding time of 600 min. After heating is completed, take out the sample after it cools naturally to room temperature with the furnace;

[0053] The 4H-SiC wafer is subjected to dry oxidation in an air atmosphere at 1050 °C for 30 min to obtain an oxide layer;

[0054] Using a spin coater, spin coat polystyrene (PS) microspheres with a diameter of about 100 nm on a 4H-SiC wafer at 2000 rpm for 2 min. Heat the PS microspheres on a graphite hot plate at 250 °C for 15 min, then the PS microspheres shrink to about 60 nm. At this time, the interval between PS microspheres is about 80 nm, and they adhere more firmly. Self-assemble to form a monolayer film, then evaporate and deposit gold. Finally, ultrasonically clean in absolute ethanol for 20 min to remove the PS microspheres, dry, and obtain a honeycomb-like gold nanopattern, which is used as a catalyst template;

[0055] Place the 4H-SiC wafer with the honeycomb-like gold nanopattern into a mold as the anode. The C surface (ground surface) of the 4H-SiC wafer contacts the copper sheet, and the graphite plate is used as the cathode. Connect the wires and immerse them in an etching solution mixed with hydrofluoric acid, ethanol, and hydrogen peroxide with a volume ratio of 3.5:6:1. Etch for 25 min under a pulsed current with a current density of 130 mA / cm 2 where the cycle time is 0.8 ms and the pause time is 0.4 ms;

[0056] Change the pulsed current to a direct current and etch for 30 s for stripping. Strip the 4H-SiC wafer, take it out and dry it. Use double-sided tape to achieve the large-area stripping of the 4H-SiC nanowire array film from the 4H-SiC wafer substrate, and then remove the double-sided tape with ethanol.

[0057] Example 4

[0058] First, cut an industrial-grade 4H-SiC wafer into 4H-SiC wafers with a size of 0.7×1.5 cm 2 Ultrasonically clean in acetone and deionized water for 15 min in sequence, then immerse in a mixed solution of hydrofluoric acid and ethanol with a volume ratio of 1:1 for 120 s. After taking out, place the 4H-SiC wafer in an oven at 60 °C and dry for 10 min;

[0059] After cleaning, mix the 4H-SiC wafer and ammonium chloride (p-type doping source) evenly at a mass ratio of 10:1, then seal them in a quartz tube with a tube length of 15 cm, an inner tube diameter of 1 cm, and a tube wall thickness of 2 mm. The pressure inside the sealed quartz tube is 1 millitorr. Place the sealed quartz tube in a muffle furnace and heat it. The heating rate is 3-10 degrees Celsius per minute, the heating temperature is 1100 °C, and the holding time is 180 min. After heating is completed, take out the sample and let it cool to room temperature naturally with the furnace;

[0060] The 4H-SiC wafer is subjected to dry oxidation in an air atmosphere at 1100 °C for 30 min to obtain an oxide layer of about 200 nm;

[0061] Spin coat polystyrene (PS) microspheres with a diameter of about 100 nm on a silicon carbide wafer at 2000 rpm for 3 min using a spin coater. Heat it on a graphite hot plate at 250 °C for 15 min to shrink it to about 60 nm. At this time, the interval between the small balls is about 80 nm, and they adhere more firmly. Self-assemble to form a monolayer film, then evaporate and deposit gold. Finally, ultrasonically clean in absolute ethanol for 20 min to remove the PS microspheres, dry, and obtain a honeycomb gold nano-pattern, which is used as a catalyst template;

[0062] Use the dried 4H-SiC wafer with a honeycomb gold nano-pattern as the anode, a graphite plate as the cathode, connect the wires, and immerse it in an etching solution mixed with hydrofluoric acid, ethanol, and hydrogen peroxide with a volume ratio of 3.5:6:1. Etch and process for 20 min under a pulsed current with a current density of 140 mA / cm 2 Then take it out. Among them, the cycle time is 0.8 ms and the pause time is 0.4 ms;

[0063] Change the pulsed current to a direct current, etch for 30 s for stripping, take it out and dry. Use double-sided tape to realize the large-area stripping of the 4H-SiC nanowire array film, and then remove the double-sided tape with ethanol. Its microscopic morphology is as shown in the appendix Figure 4 As shown, it can be clearly seen that its morphology is due to the excessive voltage resulting in the collapse of the nanowires, and its morphology is not as regular as the sample prepared under the conditions of Example 1.

[0064] Comparative Example 1

[0065] First cut the industrial-grade 4H-SiC wafer into 4H-SiC wafers with a size of 0.7×1.5 cm 2 Ultrasonically clean in acetone and deionized water for 15 min respectively, then immerse it in a mixed solution of hydrofluoric acid and ethanol with a volume ratio of 1:1 for 120 s. After taking it out, place the 4H-SiC wafer in an oven at 60 °C and dry for 10 min;

[0066] After cleaning, mix the 4H-SiC wafer and ammonium chloride (p-type doping source) evenly at a mass ratio of 10:1, and seal it in a quartz tube with a tube length of 15 cm, an inner tube diameter of 1 cm, a tube wall thickness of 2 mm, and a pressure of 1 millitorr after sealing. Place the sealed quartz tube in a muffle furnace and heat it. The heating rate is 10 °C / min, the heating temperature is 1200 °C, and the holding time is 180 min. After heating is completed, the sample is taken out after natural cooling to room temperature with the furnace;

[0067] The 4H-SiC wafer is subjected to dry oxidation in an air atmosphere at 1100 °C for 40 min to obtain an oxide layer of about 200 nm;

[0068] Using a spin coater, spin coat polystyrene (PS) microspheres with a diameter of about 100 nm on a silicon carbide wafer at 2000 rpm for 3 min. Heat it on a graphite hot plate at 250 °C for 15 min to shrink it to about 60 nm. At this time, the spacing between the microspheres is about 80 nm, and they adhere more firmly. Self-assemble to form a monolayer film, then evaporate and deposit gold. Finally, ultrasonically clean the PS microspheres in absolute ethanol for 20 min, dry them, and obtain a honeycomb gold nano-pattern, which is used as a catalyst template;

[0069] Place the 4H-SiC wafer with the honeycomb gold nano-pattern into a mold as the anode. The C surface of the 4H-SiC wafer is in contact with the copper sheet. Use a graphite plate as the cathode, connect the wires, and immerse them in an etching solution composed of hydrofluoric acid, ethanol, and hydrogen peroxide with a volume ratio of 2.5:6:1. Etch and process for 20 min under a direct current density of 100 mA / cm 2 of direct current;

[0070] Apply an external direct current, etch for 30 s for stripping, take it out and dry it. Use double-sided tape to realize the large-area stripping of the 4H-SiC nanowire array film, and then remove the double-sided tape with ethanol. Its microscopic morphology is as Figure 3 shown. It can be clearly seen that its morphology is not as regular as that of the sample prepared by using pulsed current in Example 1.

[0071] Through the characterization, performance test results and comparison of Example 1, 4, and Comparative Example 1, it can be concluded that the 4H-SiC thin film prepared by the method of Example 1 has good optoelectronic response performance and great potential in the field of optoelectronic detection.

Claims

1. A method for preparing a patterned 4 H -SiC nanowire array thin film, characterized in that Including: Step 1: Mix the 4 H -SiC wafer evenly with a p-type doping source, and perform heat treatment in a sealed space to obtain the doped 4 H -SiC wafer; wherein, the heat treatment is carried out by heating at a heating rate of 3-10 °C / min to 1000-1200 °C and holding for 60-600 min; Step 2: subject the doped 4 H -SiC wafer to dry oxidation to obtain a 4 H -SiC wafer covered with an oxide layer; wherein, the dry oxidation is carried out in an air atmosphere at 1000 - 1100 °C for heat preservation for 15 - 40 min; Step 3: Spin-coat the polystyrene microsphere solution on the 4 H H -SiC wafer, heat to shrink the polystyrene microspheres and self-assemble them into a monolayer film, then evaporate and deposit gold, and use absolute ethanol to remove the polystyrene microspheres to obtain a 4 H H -SiC wafer with gold nanopatterns; Step 4, contact the 4 H -SiC wafer with a copper plate as the anode, and an etching solution composed of hydrofluoric acid, ethanol, and hydrogen peroxide as the electrolyte. Apply a pulsed current in a three-electrode system to etch the 4 H -SiC wafer with gold nanometer patterns, and form a patterned 4 H -SiC nanowire array film on the 4 H -SiC wafer with gold nanometer patterns, and then strip to obtain the patterned 4 H -SiC nanowire array film; wherein, the stripping is specifically: first use a direct current to strip the 4 H -SiC wafer from the copper plate, dry it, and then use double-sided tape to strip the patterned 4 H -SiC nanowire array film from the 4 H -SiC wafer.

2. The patterning 4 according to claim 1 H - A method for preparing a SiC nanorod array thin film, characterized in that In Step 1, the 4 H -SiC wafer is an N-type 4 H -SiC wafer with a crystal phase of <1120>, and the p-type doping source is ammonium chloride or aluminum chloride.

3. The method for preparing a patterned 4 H -SiC nanowire array thin film, characterized in that In step 3, the heating temperature is 250 °C and the heating time is 15 min.

4. The patterning 4 according to claim 1 H - A method for preparing a SiC nanorod array thin film, characterized in that In step 4, the volume ratio of hydrofluoric acid, ethanol and hydrogen peroxide is (2.5 - 3.5): 6:

1.

5. The method for preparing a patterned 4 H -SiC nanorod array thin film, characterized in that In Step 4, the current density used for the etching process is 100 - 140 mA / cm 2 , and the etching time is 15 - 25 min.

6. Patterned 4 H -SiC nanorod array thin film obtained by the preparation method according to any one of claims 1-5.

7. The optoelectronic detection device based on the patterned 4 H -SiC nanorod array thin film as claimed in claim 6.

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