A ternary oxide narrow-band solar blind ultraviolet light detector and a preparation method thereof

Abstract

The present application relates to the technical field of photoelectric detection, and particularly relates to a ternary oxide narrow-band solar blind ultraviolet photodetector and a preparation method thereof. The present application uses a magnetron sputtering technology to realize non-equilibrium state growth of a BSnO thin film, and completes band regulation of the thin film, so that SnO2 is regulated to a wide band gap suitable for SBUV detection. On the basis of the above-mentioned thin film, a graphene / BSnO / silicon carbide heterojunction photovoltaic detector and a MSM structure narrow-band photoconductive detector are prepared. The photoconductive detector comprises, from bottom to top, a sapphire substrate, BSnO and interdigital metal electrodes. The two detectors prepared by the present application both exhibit narrow-band detection characteristics. The photoconductive detector exhibits a relatively narrow detection interval and extremely high responsivity, and can detect extremely weak solar blind ultraviolet signals. The photovoltaic detector exhibits an ultrahigh on-off ratio and extremely fast response speed under 0 bias, and can cope with detection of instantaneous solar blind ultraviolet signals.

Description

Technical Field

[0001] This invention relates to the field of photoelectric detection technology, specifically to a ternary oxide narrowband solar-blind ultraviolet detector and its preparation method. Background Technology

[0002] Solar-blind ultraviolet (SBUV) detectors, due to their immunity to solar radiation interference, have important applications in corona detection, ultraviolet reconnaissance, and near-Earth communication. Typically, wide-bandgap semiconductor materials with band gaps greater than 4.4 eV are used to fabricate suitable SBUV detectors, such as Ga₂O₃, BN, and diamond. These materials offer advantages such as low operating voltage, high stability, and small size. To accelerate the research and development of high-performance SBUV detectors, researchers have begun to manipulate the bandwidth of semiconductor materials through bandgap engineering, using materials like MgZnO and AlGaN to fabricate SBUV detectors. However, the limited variety of semiconductor materials with suitable bandwidths still does not meet the needs of detector development, necessitating further expansion of SBUV detection research.

[0003] SnO2, as a wide-bandgap metal oxide semiconductor, possesses stable physical and chemical properties, high electron mobility, and good electrical conductivity. Furthermore, due to its excellent optical and electrical characteristics, it has found widespread application in fields such as transparent conductive films (TCOs), gas sensors, and short-wavelength optoelectronic devices, and holds promise for the fabrication of solar-blind ultraviolet (UV) photodetectors. Currently, the main challenges in fabricating SnO2-based UV photodetectors are: first, the bandgap size of pure SnO2 is insufficient to meet the bandgap requirements of the matrix material for UV photodetectors; second, SnO2 itself contains a large number of electronic background carriers due to donor defect levels such as oxygen vacancies. These high concentrations of electrons result in a high dark current in the fabricated detector, severely affecting the detection sensitivity and detectivity; third, these oxygen vacancies can also form numerous trap centers and cause surface oxygen adsorption, which severely inhibits the recombination of photogenerated electrons and holes, producing a significant and persistent photoconductive effect and significantly prolonging the photoresponse time of the detector. The key to the further development of SnO2-based ultraviolet detectors lies in how to widen the band gap of SnO2 to meet the requirements of solar-blind ultraviolet detectors, and how to improve the detectivity and response speed of SnO2-based solar-blind ultraviolet detectors. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, the present invention aims to provide a method for fabricating a ternary oxide narrowband solar-blind ultraviolet (SBUV) detector. Non-equilibrium growth of a BSnO thin film is achieved using magnetron sputtering, and bandgap modulation is performed, allowing SnO2 with a bandgap of 3.6 eV to be tuned to a wide bandgap suitable for SBUV detection. Based on this thin film, a graphene / BSnO / silicon carbide heterojunction photovoltaic detector and a high-performance narrowband photoconductive detector with an MSM structure are fabricated. Both types of detectors exhibit narrowband detection characteristics.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] This invention provides a method for preparing a BSnO thin film, wherein the BSnO thin film is grown on a substrate by magnetron sputtering technology, using high-purity B and Sn targets, and the working atmosphere is Ar and O2. After growth, the BSnO thin film is annealed.

[0007] Preferably, the substrate temperature is 290-300K, the flow rates of the sputtering gases Ar and O2 are 15 sccm and 10 sccm, respectively, and the working pressure is 0.35 Pa.

[0008] Preferably, the annealing process is performed at 800–900°C for 30 seconds.

[0009] The present invention also provides a ternary oxide narrowband solar-blind ultraviolet detector, wherein the detector is a metal-ternary oxide semiconductor-metal structure narrowband solar-blind ultraviolet detector, and the detector comprises, from bottom to top, a sapphire substrate, a BSnO thin film, and interdigitated metal electrodes, wherein the BSnO thin film is grown on the sapphire substrate by the preparation method described above.

[0010] Preferably, the thickness of the BSnO thin film is 150–200 nm.

[0011] Preferably, the interdigitated metal electrode is a Ti / Ag interdigitated electrode.

[0012] Preferably, the Ti / Ag interdigitated electrode has a Ti layer with a thickness of 10 nm near the BSnO thin film; an Au layer with a thickness of 90 nm is placed on top of the Ti layer; and the spacing between each interdigitate is 100 μm.

[0013] The present invention also provides a method for fabricating the above-mentioned ternary oxide narrowband solar-blind ultraviolet detector. First, a BSnO thin film is grown on a sapphire substrate by magnetron sputtering technology. Then, Ti and Ag are sputtered sequentially on the thin film by mask sputtering technology to form Ti / Ag interdigitated electrodes, thereby obtaining a ternary oxide narrowband solar-blind ultraviolet detector.

[0014] Preferably, the Ti / Ag interdigitated electrode is grown on a thin film using mask sputtering technology. A customized mask is placed on a BSnO thin film, and Ti and Ag are sputtered sequentially on the film using magnetron sputtering technology to form the Ti / Ag interdigitated electrode. The specific parameters of the magnetron sputtering process are as follows: high-purity Ti and Ag targets are used for growth, the working atmosphere is Ar gas, the flow rate of the sputtering gas Ar is 30 sccm, the working pressure is 0.35 Pa, and the sputtering times for Ti and Ag targets are 10 min and 60 min, respectively.

[0015] This invention also provides a method for preparing a graphene / BSnO / silicon carbide heterojunction photovoltaic detector, comprising the following steps:

[0016] S1. First, a BSnO thin film is grown on a SiC substrate using the preparation method described above.

[0017] S2. Graphene on a copper substrate is transferred to the surface of a BSnO thin film using a chemical transfer method.

[0018] S3. A Ti / Au electrode is deposited on the surface of graphene, and an Ag electrode is deposited on a SiC substrate to prepare a graphene / BSnO / silicon carbide heterojunction photovoltaic detector.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] This invention utilizes magnetron sputtering technology to achieve non-equilibrium growth of BSnO thin films and completes bandgap modulation of the films, enabling SnO2 to be tuned to a wide bandgap suitable for SBUV detection. Based on these films, a graphene / BSnO / silicon carbide heterojunction photovoltaic detector and a narrowband photoconductive detector with an MSM structure are fabricated. The photoconductive detector, from bottom to top, comprises a sapphire substrate, BSnO, and interdigitated metal electrodes. Both detectors fabricated in this invention exhibit narrowband detection characteristics. The photoconductive detector demonstrates a narrow detection range and extremely high responsivity (113 A / W), capable of detecting extremely weak solar-blind ultraviolet signals. The photovoltaic detector exhibits an ultra-high on / off ratio and extremely fast response speed at zero bias, capable of detecting transient solar-blind ultraviolet signals. This invention provides a novel research direction for SBUV detection. Attached Figure Description

[0021] Figure 1 This document presents the growth mechanism and material characterization of BSnO thin films, including: (a) a schematic diagram of the magnetron sputtering growth mechanism of BSnO thin films; (b) SEM images of cross-sections of BSnO thin films and the distribution of various elements on the surface; (c) XPS spectra of BSnO thin films with different compositions; (d) UV-Vis transmission spectra of BSnO thin films with different compositions; and (e) (αhv) spectra of BSnO thin films with different compositions.2 Spectrum, inset showing the relationship between the calculated band gap of the thin film and the B content; (f) Schematic diagram of the bandgap modulation principle of BSnO thin film;

[0022] Figure 2 The structure and solar-blind ultraviolet detection performance of the BSnO thin film-based detectors are shown in the following figures: (a) schematic diagram of the detector structure; (b) current-voltage curve of BSnO detector 1; (c) current-voltage curve of BSnO detector 2; (d) current-voltage curve of BSnO detector 3; (e) relationship between photocurrent and B content; (f) relationship between responsivity and B content under different voltages.

[0023] Figure 3 The response spectra and narrowband detection mechanisms of BSnO thin film-based detectors are presented, including (a) the response spectrum of BSnO detector 1; (b) the response spectrum of BSnO detector 2; (c) the response spectrum of BSnO detector 3; (d) the relationship between cutoff wavelength and B content; (e) the relationship between absorption peak and B content; (f) the relationship between full width at half maximum (FWHM) and B content; (g) the mechanism analysis of narrowband detection based on BSnO thin film; and (h) the relationship between photocurrent and responsivity and absorption peak.

[0024] Figure 4 The structure and detection capability of the graphene / BSnO / silicon carbide heterojunction photovoltaic detector were tested, including: (a) a schematic diagram of the detector structure; (b) current-voltage curves of Ag-SiC and Au / Ti-graphene; (c) ultraviolet-visible transmission spectrum of graphene; (d) current-voltage curves of BSnO detector 4 under darkness and different light intensities; (e) current-voltage curves of BSnO detector 5 under darkness and different light intensities; (f) current-voltage curves of BSnO detector 6 under darkness and different light intensities; (g) relationship between photocurrent and light intensity; (h) relationship between responsivity and light intensity; and (i) relationship between open-circuit voltage of the detector and light intensity.

[0025] Figure 5 The stability and response speed of graphene / BSnO / silicon carbide heterojunction photovoltaic detectors are shown in (a) current-time curves of detectors with different B contents; (b) rise time of the detector; and (c) decay time of the detector. Detailed Implementation

[0026] The specific embodiments of the present invention will be further described below. It should be noted that these descriptions are for the purpose of aiding understanding the present invention, but do not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0027] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods, and the experimental materials used in the following embodiments are all available through conventional commercial channels.

[0028] Example 1: Fabrication of a narrowband solar-blind ultraviolet photodetector based on BSnO thin film

[0029] S1. Select a C-side sapphire as the substrate. The cleaning process is as follows: Immerse the substrate in about 15 mL of acetone, anhydrous ethanol and deionized water in sequence and ultrasonically clean each for 15 min. After taking it out, rinse it with running deionized water and then blow it dry with dry N2 gas for later use.

[0030] S2. The cleaned sapphire substrate is placed into the deposition chamber. First, a BSnO thin film 1 is grown on the sapphire substrate by magnetron sputtering. Finally, the film is placed in an annealing furnace and annealed at 900℃ for 30s. High-purity B target (99.999%) and Sn target (99.99%) are used for growth. The specific parameters of the magnetron sputtering technology are as follows: the pressure in the sputtering chamber is maintained at 0.35Pa, the flow rates of sputtering gases Ar and O2 are 15sccm and 10sccm, respectively, the substrate temperature is 290K, the sputtering power is 50W for B target and 20W for Sn target, and the sputtering time is 72min. The thickness of the obtained BSnO thin film is about 200nm.

[0031] S3. The grown BSnO was masked with an interdigitated mask, and a 10 nm thick Ti layer and a 90 nm thick Au layer were successively sputtered using DC magnetron sputtering to obtain a 100 nm thick interdigitated Ti / Au metal electrode. The finger width and spacing of the Ti / Ag interdigitated electrode were both 100 μm, and the effective irradiation area was approximately 0.045 cm². 2 The specific conditions for growing interdigitated electrodes were as follows: the pressure in the sputtering chamber was maintained at 0.35 Pa, the sputtering gas (Ar) flow rate was 30 sccm, the sputtering times for Ti target (99.995%) and Ag target (self-made) were 10 min and 60 min, respectively, and the substrate temperature was room temperature.

[0032] S4. The narrowband solar-blind ultraviolet photodetector based on BSnO thin film obtained through the above steps is biased on both sides of the interdigitated electrode. The current flows in from the positive electrode, passes through the BSnO thin film, and flows out from the negative electrode, forming a metal-semiconductor-metal (MSM) type solar-blind ultraviolet photodetector, denoted as BSnO detector 1.

[0033] Example 2: Fabrication of a narrowband solar-blind ultraviolet photodetector based on BSnO thin film

[0034] The fabrication method of the narrowband solar-blind ultraviolet detector based on BSnO thin film in this embodiment is the same as that in Embodiment 1, except that the sputtering power is changed to 50W for the B target and 40W for the Sn target, and the sputtering time is changed to 60min to obtain BSnO thin film 2. The detector based on BSnO thin film 2 is denoted as BSnO detector 2.

[0035] Example 3: Fabrication of a narrowband solar-blind ultraviolet photodetector based on BSnO thin film

[0036] The fabrication method of the narrowband solar-blind ultraviolet detector based on BSnO thin film in this embodiment is the same as that in Embodiment 1, except that the sputtering power is changed to 50W for the B target and 60W for the Sn target, and the sputtering time is changed to 48min, so as to obtain BSnO thin film 3. The detector based on BSnO thin film 3 is denoted as BSnO detector 3.

[0037] Experimental Example 1: Characterization of BSnO thin films and narrowband solar-blind ultraviolet photodetectors based on BSnO thin films

[0038] 1. Preparation principle and characterization of BSnO thin films

[0039] Figure 1 This reveals the principle of epitaxial growth of BSnO thin films on sapphire substrates. Electrons fly towards the substrate under the influence of the electric field between the target and the substrate. During this process, they collide with Ar atoms and ionize to produce Ar ions and new electrons. The new electrons are bound by the magnetic field on the target surface and move at high speed on the target surface, colliding with Ar atoms to produce more Ar ions. The Ar ions bombard the target under the influence of the electric field, and the sputtered B atoms and Sn atoms react with oxygen and are finally deposited on the substrate to form a BSnO thin film.

[0040] Scanning electron microscope cross-sectional images of BSnO thin films 1, 2, and 3 are shown below. Figure 1 As shown in b, the film surface is smooth and the thickness is uniform, approximately 200 nm. Elemental surface scanning analysis of BSnO films 1, 2, and 3 using an X-ray energy dispersive spectroscopy (Regulus 8100) clearly shows the presence of B, Sn, and O elements, which are uniformly distributed. XPS spectra of BSnO films 1, 2, and 3 were analyzed using an X-ray photoelectron spectroscopy (Thermo Fisher ESCBAB 250Xi), and the XPS spectra are shown below. Figure 1 As shown in Figure c, this indicates the presence of B, Sn, and O elements in the thin film, and... Figure 1 The test results for b were consistent, and the atomic ratio of B to Sn in the BSnO film was measured and determined. The B contents in BSnO films 1, 2, and 3 were 60%, 42%, and 35%, respectively. The transmission spectra of the three different BSnO films 1, 2, and 3 were analyzed using a UV-Vis spectrophotometer (Shimadzu UV-2600). The spectra are shown below. Figure 1As shown in Figure d, all three groups of BSnO films exhibit good SBUV absorption capabilities. The absorption edge shows a blue shift with increasing B content, indicating that the band gap widens with increasing B content. The band gap of the BSnO films was calculated using the Tauc rule, and the results are shown in Figure d. Figure 1 As shown in Figure e, the band gaps of BSnO films 1, 2, and 3 are 5.29 eV, 4.38 eV, and 4.13 eV, respectively. The inset shows that the film band gap and B content have a certain linear relationship.

[0041] The above results indicate that the present invention has completed the bandgap engineering of BSnO thin films. To further elucidate the mechanism of bandgap modulation, the present invention has drawn the following diagrams: Figure 1 The schematic diagram is shown in f. Due to the difference in band gaps between boron oxide and tin oxide, the band gap of the BSnO thin film changes with the composition. Therefore, bandgap modulation can be achieved by adjusting the film composition. When the film is exposed to light with photon energy greater than its band gap, electrons in its valence band will jump to the conduction band, generating a large number of charge carriers. Under the action of an external electric field, these photogenerated charge carriers will move directionally, thus generating a significant photocurrent. Based on this principle, this invention fabricates a photoconductive SBUV detector with an MSM structure on three sets of BSnO thin films, as shown in the diagram. Figure 2 As shown in figure a, a series of tests were conducted on their detection performance.

[0042] 2. Detection performance analysis of BSnO thin film-based detectors

[0043] The current-voltage curves of BSnO detectors 1, 2, and 3 in dark and illuminated conditions are shown below. Figure 2 As shown in b to d, the photo-to-dark current ratio (PCDR) of BSnO detector 1 with a boron content of 60% in the thin film is 0.9 × 10⁻⁶. 3 The PCDRs of BSnO detectors 2 and 3 are 1.4 × 10⁻⁶. 4 and 0.9×10 4 The relationship between the detector current and the boron content in the thin film is as follows: Figure 2 As shown in Figure e, the dark current decreases with increasing boron content because tin oxide has a lower resistivity compared to boron oxide. With increasing boron content, the band gap of the film increases, allowing it to absorb only SBUV light with higher photon energy. These shorter wavelengths are less likely to penetrate the film to generate more charge carriers, leading to a decrease in photocurrent.

[0044] Responsivity is an important parameter reflecting detector performance, which can be expressed as R = (I light -I dark ) / (A·P inc The calculation yields R, where R is the responsivity and I is the response. light It is the electric current generated by light, I darkIt is the dark current, and A is the area of ​​the device exposed to light (0.045 mm²). 2 ), P inc This refers to the intensity of the incident light. The relationship between the detector's responsivity and the B content is shown in... Figure 2 In the f-type detector, thanks to its ultra-high PDCR, the responsivity trend is consistent with the photocurrent. The detector's responsivity has a good linear relationship with the operating voltage in the 0-1V range, indicating that it can operate at a relatively low bias voltage. When the bias voltage is 1V, the BSnO detector with a boron content of 35% can achieve a maximum responsivity of 113 A / W.

[0045] 3. The effect of BSnO thin films with different boron contents on the narrowband detection performance of photovoltaic devices

[0046] This invention tested the response spectra of three groups of BSnO detectors 1, 2, and 3 with different B components, and the results are as follows: Figure 3 As shown in Figure 6, all three detectors exhibited obvious narrowband detection characteristics, and the trend of peak responsivity variation was consistent with that in Figure 6f. Figure 3 d and Figure 3 e shows the relationship between the detector's cutoff wavelength and absorption peak and the boron content in the BSnO thin film. As the boron content increases, the band gap of the film widens, leading to a blue shift in both the cutoff wavelength and the absorption peak. The relationship between the full width at half maximum (FWHM) and the boron content is shown in Figure [e]. Figure 3 As shown in f, with increasing B content, the full width at half maximum (FWHM) gradually narrows, reaching a width of only 34 nm. To illustrate the narrow-band detection mechanism based on BSnO thin films, in Figure 3 Figure 7h illustrates the relevant schematic. Short wavelengths in the SBUV range have weak penetration. When these amorphous BSnO thin films with strong surface recombination are irradiated, most of the generated charge carriers recombine at the film surface, with only a small number forming a current under the influence of an applied electric field. Longer wavelengths, however, can penetrate deeper into the film. While some of the generated charge carriers recombine at the surface, a portion still forms a significant current under the influence of an applied electric field. Therefore, once the detector's responsivity reaches its peak, it decreases as the wavelength shortens, resulting in a narrower detection range. Furthermore, the photocurrent and responsivity also decrease as the peak wavelength shortens, as shown in Figure 7h.

[0047] MSM-structured photoconductive detectors exhibit extremely high responsivity but relatively slow response speed. In certain detection applications, response speed is a crucial performance indicator; therefore, this invention fabricates a graphene / BSnO / silicon carbide heterojunction photovoltaic detector based on the aforementioned BSnO thin film.

[0048] Example 4: Fabrication of a graphene / BSnO / silicon carbide heterojunction photovoltaic detector

[0049] 1. First, a BSnO thin film 1 is grown on a SiC substrate by magnetron sputtering, and the magnetron sputtering process is the same as in Example 1;

[0050] 2. Prepare an ammonium persulfate solution with a molar concentration of 0.1 mol / L; first spin-coat a layer of PMMA onto graphene / Cu, then heat to solidify the PMMA, and then immerse the graphene copper foil covered with PMMA in the ammonium persulfate solution with the copper side facing down until the copper foil is completely dissolved;

[0051] 3. Using a SiC substrate with a raw BSnO thin film, the graphene is retrieved and baked on a 70°C heating plate until it is dry;

[0052] 4. Soak the dried SiC substrate in acetone, anhydrous ethanol, and ultrapure water for 10 minutes in sequence to remove residual PMMA on the graphene surface. Finally, bake it on a 70°C hot plate until dry for later use.

[0053] 5. A Ti / Au electrode is thermally deposited on graphene, and finally an Ag electrode is deposited on a SiC substrate to obtain a graphene / BSnO / silicon carbide heterojunction photovoltaic detector, denoted as BSnO detector 4.

[0054] Example 5: Fabrication of a graphene / BSnO / silicon carbide heterojunction photovoltaic detector

[0055] The preparation method of the graphene / BSnO / silicon carbide heterojunction photovoltaic detector in this embodiment is the same as that in Example 4, except that the magnetron sputtering process of the BSnO thin film is the same as that in Example 2. The graphene / BSnO / silicon carbide heterojunction photovoltaic detector obtained is referred to as BSnO detector 5.

[0056] Example 6: Fabrication of a graphene / BSnO / silicon carbide heterojunction photovoltaic detector

[0057] The preparation method of the graphene / BSnO / silicon carbide heterojunction photovoltaic detector in this embodiment is the same as that in Example 4, except that the magnetron sputtering process of the BSnO thin film is the same as that in Example 3. The graphene / BSnO / silicon carbide heterojunction photovoltaic detector obtained is referred to as BSnO detector 6.

[0058] Example 2: Characterization of a graphene / BSnO / silicon carbide heterojunction photovoltaic detector

[0059] 1. Testing the structure and detection capability of photovoltaic detectors

[0060] The structures of the graphene / BSnO / silicon carbide heterojunction photovoltaic detectors in Examples 4, 5, and 6 are as follows: Figure 4 As shown in Figure a, its extremely short transmission distance in the vertical direction can effectively improve the response speed. Figure 4b shows the current-voltage curves for Ag-SiC and Au / graphene, indicating that the contact between the Au / Ti electrode and graphene is an ohmic contact, while the contact between Ag and the SiC substrate is a quasi-ohmic contact. The visible-ultraviolet transmission spectrum of graphene is shown below. Figure 4 As shown in c, graphene has a high transmittance for light in the 200-800nm ​​range and can be considered transparent.

[0061] The current-voltage curves of photovoltaic detectors based on BSnO thin films of different compositions were tested under dark conditions and under ultraviolet light irradiation at different incident powers of 231 nm, 254 nm, and 272 nm. The results are as follows: Figure 4 As shown in df, the detectors all exhibited ultra-high PDCR at 0 bias. Furthermore, the current-voltage curves of photovoltaic detectors based on BSnO thin films of different compositions were tested under different light intensities. The relationship between photocurrent and light intensity at 0 bias is shown in the figure. Figure 4 As shown in g, the photocurrent increases with increasing light intensity. The relationship between responsivity and light intensity is illustrated in... Figure 4 In h, it can be seen that the responsivity remains basically stable under different light intensities, indicating that the detector can output stable results in practical applications. Because the detector with 35% boron content has an extremely low open-circuit voltage, it exhibits a lower responsivity at 0 bias than the detector with 42% boron content. The open-circuit voltage increases with increasing light intensity, such as... Figure 4 The value 'i' indicates that the open-circuit voltage has not reached saturation within the tested light intensity range. The open-circuit voltage of a photovoltaic detector is determined by the built-in electric field between the BSnO thin film and SiC. When the boron content in the BSnO thin film is 35%, the Fermi level of the film is relatively close to that of SiC, resulting in a weaker built-in electric field. As the boron content decreases, the gap between the Fermi levels of the film and SiC increases, thus the open-circuit voltage gradually increases.

[0062] 2. The effect of BSnO thin films with different boron contents on the detection performance of the device.

[0063] Stability and response speed are also important indicators of detector performance. The photoelectric response of the device in a periodically changing light and dark environment was tested by periodically switching the light source on and off. Figure 5 Figure a shows the current-time relationship curves for BSnO devices with different boron contents under different operating bias voltages. All three detector groups exhibited extremely fast response speeds and maintained these speeds and stable photocurrents even after multiple cycles, demonstrating that the detector can stably repeat operations multiple times. To more intuitively illustrate the detector's response speed, in... Figure 5 b and Figure 5c. The rise time and fall time of BSnO devices with different B contents under 0 bias voltage were calculated respectively. The calculation shows that the rise time and fall time of BSnO devices with 60% B content under 0 bias voltage are extremely short, with the shortest being only 43ms and 40ms respectively. Such short response time is beneficial to the application of this device in instantaneous SBUV signal detection.

[0064] As described above, Examples 1-6 involved growing BSnO thin films via magnetron sputtering and achieving bandgap engineering of BSnO. Based on these BSnO thin films, MSM-structured photoconductive detectors (BSnO detectors 1-3) and graphene / BSnO / silicon carbide heterojunction photovoltaic detectors (BSnO detectors 4-6) were fabricated to handle the detection of extremely weak and transient signals, respectively. Both types of detectors exhibited narrowband detection characteristics.

[0065] The embodiments of the present invention have been described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and these variations still fall within the protection scope of the present invention.

Claims

1. A method for preparing a BSnO thin film, characterized in that, The BSnO thin film was grown on the substrate by magnetron sputtering. High-purity B and Sn targets were used for growth, and the working atmosphere was Ar and O2. After growth, the BSnO thin film was annealed at 900 °C for 30 s. The substrate temperature is 290 K, the flow rates of Ar gas and O2 gas are 15 sccm and 10 sccm respectively, and the working pressure is 0.35 Pa.

2. A ternary oxide narrowband solar-blind ultraviolet detector, characterized in that, The detector is a narrowband solar-blind ultraviolet detector with a metal-ternary oxide semiconductor-metal structure. The detector comprises, from bottom to top, a sapphire substrate, a BSnO thin film, and interdigitated metal electrodes. The BSnO thin film is grown on the sapphire substrate by the preparation method described in claim 1.

3. A ternary oxide narrowband solar-blind ultraviolet detector according to claim 2, characterized in that, The thickness of the BSnO thin film is 150~200 nm.

4. A ternary oxide narrowband solar-blind ultraviolet detector according to claim 2, characterized in that, The interdigitated metal electrode is a Ti / Ag interdigitated electrode.

5. A ternary oxide narrowband solar-blind ultraviolet detector according to claim 4, characterized in that, The Ti / Ag interdigitated electrode has a Ti layer with a thickness of 10 nm near the BSnO thin film; an Ag layer with a thickness of 90 nm is placed on top of the Ti layer; and the spacing between each interdigitate is 100 μm.

6. The method for fabricating a ternary oxide narrowband solar-blind ultraviolet detector according to any one of claims 2 to 5, characterized in that, First, a BSnO thin film is grown on a sapphire substrate using magnetron sputtering technology. Then, Ti and Ag are sputtered sequentially on the thin film using mask sputtering technology to form Ti / Ag interdigitated electrodes, thus fabricating a ternary oxide narrowband solar-blind ultraviolet detector.

7. A method for fabricating a graphene / BSnO / silicon carbide heterojunction photovoltaic detector, characterized in that, Includes the following steps: S1. First, a BSnO thin film is grown on a SiC substrate using the preparation method described in claim 1; S2. Graphene on a copper substrate is transferred to the surface of a BSnO thin film using a chemical transfer method. S3. A Ti / Au electrode is deposited on the graphene surface, and an Ag electrode is prepared on a SiC substrate to obtain a graphene / BSnO / silicon carbide heterojunction photovoltaic detector.

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