A vacuum cold cathode flat-panel photodetector driven by a dual-gate thin-film transistor and a method for preparing the same

Abstract

The present invention belongs to the field of light detection, and more specifically, relates to a vacuum cold cathode flat-panel photodetector driven by a dual-gate thin-film transistor and a method for preparing the same. The flat-panel photodetector comprises a photoconductive anode substrate and a cold cathode substrate. The photoconductive anode substrate comprises an anode substrate, an anode electrode disposed on the anode substrate, and a photoelectric response layer disposed on the anode electrode. The cold cathode substrate comprises a cathode substrate, a dual-gate thin-film transistor disposed on the cathode substrate, and a cold cathode emitter disposed on the dual-gate thin-film transistor. The photoelectric response layer and the cold cathode emitter are relatively separated by an insulator and maintained in a vacuum state. The present invention improves the sensitivity of the photodetector by utilizing the photomultiplication mechanism of the electron bombardment-induced photoconductivity effect and the photomultiplication mechanism of the subthreshold current amplification effect of the thin-film transistor. The vacuum cold cathode flat-panel photodetector can also achieve high-resolution and wide linear dynamic range photodetection.

Description

Technical Field

[0001] The present invention relates to the field of light detection, and more particularly to a vacuum cold cathode flat-panel light detector driven by a dual-gate thin film transistor and a preparation method thereof. Background Art

[0002] Flat-panel photodetectors are indispensable key components in contemporary military, aerospace, industrial production and social life. Among them, day-blind ultraviolet detectors mainly detect ultraviolet light with a wavelength of 190nm-280nm, and play an important role in applications such as missile guidance, leakage detection, and fire monitoring. In these applications, detectors not only need to work in harsh environments such as high temperature, high electric field and high radiation, but also need to have photoelectric response characteristics such as high sensitivity, high resolution and wide dynamic range. Currently reported day-blind ultraviolet detectors mainly use photoconductivity or Schottky structure (Chinese patents: CN202311785581.X and CN202311653005.X). However, photoconductive detectors have disadvantages such as slow response speed and narrow dynamic range, and the detection sensitivity of Schottky structure detectors is affected by interface characteristics.

[0003] Flat-panel X-ray detection and imaging devices also have important applications in medical testing, industrial flaw detection, security and bomb disposal, and other fields. X-ray radiation is harmful to the human body, placing higher demands on the detection dose and sensitivity of X-ray detectors. Currently reported X-ray detectors primarily include indirect detectors based on scintillators and direct detectors based on semiconductors. However, indirect X-ray detection suffers from low conversion efficiency, making low-dose detection difficult. Direct X-ray detection, however, faces significant challenges due to limitations in materials, structure, and photoelectric conversion mechanisms, and its sensitivity needs to be further improved. Therefore, achieving high-sensitivity, high-resolution, and wide-dynamic-range vacuum cold-cathode photoelectric imaging devices remains a key scientific challenge in this field. In recent years, a photoconductive cold-cathode flat-panel X-ray detector (Chinese invention patent: CN113471052B) has been developed that not only enables large-area imaging but also improves X-ray detection sensitivity. However, this device also suffers from low light-to-dark current, a narrow linear dynamic range, and high detection dose. Summary of the Invention

[0004] In order to overcome at least one of the above-mentioned defects of the prior art, the present invention provides a vacuum cold cathode flat-panel photodetector driven by a dual-gate thin film transistor and a method for preparing the same.

[0005] The present invention aims to solve the above technical problems at least to a certain extent.

[0006] In order to solve the above technical problems, the technical solutions of the present invention are as follows:

[0007] A vacuum cold cathode flat-panel photodetector driven by a dual-gate thin film transistor comprises a photoconductive anode substrate, a cold cathode substrate driven by a dual-gate thin film transistor, and an isolator.

[0008] Furthermore, the photoconductive anode substrate includes an anode substrate, an anode electrode and a photoelectric response layer, the anode electrode is arranged on the surface of the anode substrate, the photoelectric response layer is arranged on the anode electrode, the cold cathode substrate includes a cold cathode emitter, a top gate, a top insulating layer, a source, a drain, a channel layer, a bottom insulating layer, a bottom gate and a cathode substrate, the bottom gate is arranged on the cathode substrate, the bottom insulating layer is arranged on the bottom gate, the channel layer is arranged on the bottom insulating layer, the source and the drain are separated by the channel layer, the top insulating layer is arranged on the channel layer, the top gate is arranged on the top insulating layer, the cold cathode emitter is arranged on the top gate, the photoconductive anode substrate and the cold cathode substrate are separated by an insulator, and there is a vacuum state between the photoelectric response layer and the cold cathode emitter.

[0009] Furthermore, the photoelectric response layer includes one or more photoconductors selected from Ga2O3, AlGaN, GaN, GaAs, a-Se, CdTe, perovskite and HgI2.

[0010] Furthermore, the photoelectric response layer also includes a P-type semiconductor, an I-type photoconductor and an N-type semiconductor in a PIN structure, the N-type semiconductor is arranged on the anode electrode, the I-type photoconductor is arranged on the N-type semiconductor, and the P-type semiconductor is arranged on the I-type photoconductor.

[0011] Furthermore, the P-type semiconductor includes any one of P-type NiO, Cu2O, CoO, Cu2S, SnO, SnS and MnO semiconductors.

[0012] Furthermore, the I-type photoconductor includes any one of I-type Ga2O3, AlGaN, GaN, GaAs, a-Se, CdTe, perovskite and HgI2 photoconductors.

[0013] Furthermore, the N-type semiconductor includes any one of N-type WO3, TiO2, Fe2O3, ZnO, V2O5, CrO3 and BaO semiconductors.

[0014] Furthermore, the cold cathode emitter includes semiconductor nanowires formed of any one of zinc oxide, copper oxide, tungsten oxide, iron oxide and molybdenum oxide.

[0015] Furthermore, the top gate is connected to a protection resistor or a voltage stabilizing diode, and the resistance range of the protection resistor is 10 2 ~10 12Ω, the stable voltage range of the voltage stabilizing diode is 5 to 50V.

[0016] A method for preparing a vacuum cold cathode flat-panel photodetector driven by a dual-gate thin-film transistor, the method being applied to the vacuum cold cathode flat-panel photodetector, comprising the following steps:

[0017] S1: Anode electrode is prepared on the surface of anode substrate using magnetron sputtering technology;

[0018] S2: using electron beam evaporation technology to prepare a photoelectric response layer on the prepared anode electrode;

[0019] S3: Using magnetron sputtering, photolithography and wet etching techniques to prepare the bottom gate, channel layer, source, drain and top gate on the surface of the cathode substrate;

[0020] S4: preparing a bottom insulating layer and a top insulating layer (8) using plasma enhanced chemical vapor deposition technology;

[0021] S5: preparing a cold cathode emitter on the top grid;

[0022] S6: The photoelectric response layer and the cold cathode emitter are separated from each other by an insulator and maintained in a vacuum state.

[0023] Furthermore, in step S5, the step of preparing a cold cathode emitter on the top grid includes:

[0024] Semiconductor nanowires, which are cold cathode emitters, are grown on the top gate using photolithography, electron beam evaporation, and thermal oxidation methods.

[0025] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0026] On the one hand, the present invention provides a photoresponse layer on the anode substrate, utilizing a photomultiplier mechanism based on the electron bombardment-induced photoconductivity effect to improve detection sensitivity. On the other hand, when the detector is exposed to light, the top gate of the dual-gate thin-film transistor connected to the cold cathode emitter generates a positive charge, forming a potential difference with the channel layer of the dual-gate thin-film transistor, causing the threshold voltage of the dual-gate thin-film transistor to decrease. This enables a photomultiplier mechanism based on the subthreshold current amplification effect of the dual-gate thin-film transistor, achieving low dark current, high photocurrent, and high sensitivity. Furthermore, the dual-gate thin-film transistor utilizes the current-limiting properties of the saturation region to improve the stability of the vacuum cold cathode flat-panel photodetector, thereby enabling detection of weak light signals with a high signal-to-noise ratio and a wide linear dynamic range. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic structural diagram of the vacuum cold cathode flat-panel photodetector driven by a dual-gate thin-film transistor according to the present invention;

[0028] Figure 2 This is a schematic structural diagram of a vacuum cold cathode flat-panel photodetector driven by a dual-gate thin-film transistor based on a PIN-type photoresponse layer according to this embodiment;

[0029] Figure 3 This is a schematic diagram of the structure of a vacuum cold cathode flat-panel photodetector driven by a dual-gate thin-film transistor with a top gate connected to a protection resistor according to the present invention;

[0030] Figure 4 This is a flow chart of a method for preparing a vacuum cold cathode flat-panel photodetector driven by a dual-gate thin-film transistor according to the present invention;

[0031] Figure 5 This is a schematic diagram of the structure of a vacuum cold cathode flat-panel photodetector driven by a double-gate thin-film transistor with a top gate connected to a zener diode according to the present invention;

[0032] Figure 6 This is a surface morphology diagram of the ZnO nanowire cold cathode emitter of the present invention;

[0033] Figure 7 This is a schematic structural diagram of a vacuum cold cathode flat-panel photodetector according to this embodiment;

[0034] Figure 8 This is a schematic structural diagram of a vacuum cold cathode flat-panel photodetector driven by a single-gate thin-film transistor according to this embodiment;

[0035] Figure 9 This is a graph showing anode current-anode voltage curves of a vacuum cold cathode flat-panel photodetector described in this embodiment under different X-ray doses;

[0036] Figure 10 This is a graph showing the transfer characteristics of the thin film transistor of the vacuum cold cathode flat panel photodetector driven by the dual-gate thin film transistor described in this embodiment under different X-ray doses;

[0037] Figure 11 This is a graph showing the relationship between the thin film transistor threshold voltage and the X-ray dose of the vacuum cold cathode flat panel photodetector driven by the dual-gate thin film transistor described in this embodiment;

[0038] In the figure, 1. incident light; 2. anode substrate; 3. anode electrode; 4. photoelectric response layer; 5. insulator; 6. cold cathode emitter; 7. top gate; 8. top insulating layer; 9. source electrode; 10. drain electrode; 11. channel layer; 12. bottom insulating layer; 13. bottom gate; 14. cold cathode substrate; 15. N-type semiconductor 15; 16. I-type photoconductor; 17. P-type semiconductor; 18. cold cathode metal electrode. DETAILED DESCRIPTION

[0039] The accompanying drawings are for illustrative purposes only and are not to be construed as limiting this patent;

[0040] In order to better illustrate this embodiment, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product size;

[0041] It is understandable to those skilled in the art that some well-known structures and descriptions thereof may be omitted in the drawings.

[0042] The technical solution of the present invention is further described below with reference to the accompanying drawings and embodiments.

[0043] Example 1

[0044] A vacuum cold cathode flat panel photodetector driven by a dual-gate thin film transistor, such as Figure 1 As shown, it includes a photoconductive anode substrate, a cold cathode substrate driven by a dual-gate thin film transistor, and an isolator 5.

[0045] The photoconductive anode substrate includes an anode substrate 2, an anode electrode 3 and a photoelectric response layer 4, wherein the anode electrode 3 is arranged on the surface of the anode substrate 2, and the photoelectric response layer 4 is arranged on the anode electrode 3. The cold cathode substrate includes a cold cathode emitter 6, a top gate 7, a top insulating layer 8, a source electrode 9, a drain electrode 10, a channel layer 11, a bottom insulating layer 12, a bottom gate 13 and a cold cathode substrate 14, wherein the bottom gate 13 is arranged on the cold cathode substrate 14, the bottom insulating layer 12 is arranged on the bottom gate 13, the channel layer 11 is arranged on the bottom insulating layer 12, the source electrode 9 and the drain electrode 10 are separated by the channel layer 11, the top insulating layer 8 is arranged on the channel layer 11, the top gate 7 is arranged on the top insulating layer 8, the cold cathode emitter 6 is arranged on the top gate 7, the photoconductive anode substrate and the cold cathode substrate are separated by an insulator 5, and there is a vacuum state between the photoelectric response layer 4 and the cold cathode emitter 6.

[0046] On the one hand, a photoresponse layer is placed on the anode substrate, utilizing a photomultiplication mechanism based on the electron bombardment-induced photoconductivity effect to improve detection sensitivity. On the other hand, when the detector is illuminated by light, the top gate of the dual-gate thin-film transistor connected to the cold cathode emitter generates a positive charge, creating a potential difference with the channel layer of the dual-gate thin-film transistor, causing the threshold voltage of the dual-gate thin-film transistor to decrease. This enables a photomultiplication mechanism based on the subthreshold current amplification effect of the dual-gate thin-film transistor, achieving low dark current, high photocurrent, and high sensitivity. Furthermore, the dual-gate thin-film transistor utilizes the current-limiting properties of the saturation region to improve the stability of the vacuum cold cathode flat-panel photodetector, thereby achieving a high signal-to-noise ratio and a wide linear dynamic range for detecting weak light signals.

[0047] Example 2

[0048] This embodiment, based on the first embodiment, further discloses the following contents:

[0049] The photoelectric response layer 4 includes one or more photoconductors selected from Ga2O3, AlGaN, GaN, GaAs, a-Se, CdTe, perovskite and HgI2, and the resistance of the photoconductor is greater than 10 6 Ω.

[0050] like Figure 2 As shown, the photoelectric response layer 4 also includes a P-type semiconductor 17, an I-type photoconductor 16 and an N-type semiconductor 15 of a PIN structure, the N-type semiconductor 15 is arranged on the anode electrode 3, the I-type photoconductor 16 is arranged on the N-type semiconductor 15, and the P-type semiconductor 17 is arranged on the I-type photoconductor.

[0051] The photoelectric response layer 4 with a PIN structure increases the thickness of the photoconductive depletion layer, thereby improving the light absorption efficiency, and can increase the working electric field of the photoconductor, thereby improving the efficiency of collecting photogenerated carriers, and utilizes the impact ionization effect under a high electric field to realize an avalanche photomultiplication mechanism, thereby improving the sensitivity of the detector, reducing the dark current of the detector, thereby improving the linear dynamic range and reducing the detection dose, and utilizing the drift current of the depletion layer to achieve a fast photoelectric response.

[0052] The P-type semiconductor 17 includes any one of P-type NiO, Cu2O, CoO, Cu2S, SnO, SnS and MnO semiconductors.

[0053] The I-type photoconductor 16 includes any one of I-type Ga2O3, AlGaN, GaN, GaAs, a-Se, CdTe, perovskite and HgI2 photoconductors, which can generate electron-hole pairs under light, and the resistance of the photoconductor is greater than 10 6 Ω, which is conducive to achieving low dark current, low detection dose and wide linear dynamic range.

[0054] The preparation method of the photoconductor anode substrate is as follows: prepare a 15×15 cm 2 , 3mm thick glass was used as the anode substrate, and an ITO electrode with a thickness of 500nm was plated on the surface of the anode substrate using magnetron sputtering technology as the anode electrode; then N-type semiconductor (WO3), I-type photoconductor (Ga2O3) and P-type semiconductor (NiO) thin films were successively plated on the anode electrode as photoelectric response layers using electron beam evaporation technology, the thickness of the Ga2O3 film was 3μm, and the thickness of the WO3 and NiO films were both 100nm.

[0055] The N-type semiconductor 15 includes any one of N-type WO 3 , TiO 2 , Fe 2 O 3 , ZnO, V 2 O 5 , CrO 3 and BaO semiconductors.

[0056] The present invention sets a photoelectric response layer on the anode substrate, and can use the photoelectric multiplication mechanism of the electron bombardment induced photoconductivity effect to improve the detection sensitivity. When the detector is exposed to light, the photoelectric response layer on the anode substrate generates electron-hole pairs when exposed to light, so that the equivalent resistance of the photoelectric response layer is reduced, and the equivalent electric field of the cold cathode emitter is increased, so that the electrons emitted by the cold cathode increase. Under the action of the electric field, the electrons emitted by the cold cathode are accelerated in a vacuum to become high-energy electrons. The high-energy electrons further bombard the photoelectric response layer of the anode substrate, causing collision ionization, thereby generating multiplied carriers, that is, the photogenerated carriers are multiplied.

[0057] Example 3

[0058] This embodiment, based on Embodiments 1 and 2, further discloses the following contents:

[0059] The cold cathode emitter 6 includes semiconductor nanowires formed of any one of zinc oxide, copper oxide, tungsten oxide, iron oxide and molybdenum oxide.

[0060] Under the action of the electric field, the top gate of the dual-gate thin-film transistor connected to the cold cathode emitter generates positive charge and forms a potential difference with the channel layer of the dual-gate thin-film transistor. Under the action of the top gate voltage, the threshold voltage of the dual-gate thin-film transistor is reduced, and the transistor changes from the off state or subthreshold state to the on state, thereby realizing the photomultiplier mechanism of the current amplification effect, achieving low dark current, high photocurrent and high sensitivity. The dual-gate thin-film transistor can utilize the current limiting characteristics of the saturation region to improve the stability of the vacuum cold cathode flat-panel photodetector, thereby realizing weak light signal detection with high signal-to-noise ratio and wide linear dynamic range.

[0061] like Figure 3 As shown, the top gate 7 is connected to a protection resistor using a wire, and the resistance range of the protection resistor is 10 2 ~10 12 Ω, on the one hand, can optimize the voltage of the top gate of the dual-gate thin-film transistor, regulate the working state of the dual-gate thin-film transistor, and regulate the photoelectric response characteristics of the photodetector; on the other hand, it can limit the voltage of the top gate of the dual-gate thin-film transistor to prevent high-voltage breakdown of the dual-gate thin-film transistor.

[0062] A method for preparing a vacuum cold cathode flat panel photodetector driven by a dual-gate thin film transistor, such as Figure 4 As shown, the preparation method is applied to the vacuum cold cathode flat panel photodetector, comprising the following steps:

[0063] S1: using magnetron sputtering technology to prepare an anode electrode 3 on the surface of an anode substrate 2;

[0064] S2: using electron beam evaporation technology to prepare a photoelectric response layer 4 on the prepared anode electrode 3;

[0065] S3: using magnetron sputtering, photolithography and wet etching techniques to prepare a bottom gate 13, a channel layer 11, a source electrode 9, a drain electrode 10 and a top gate 7 on the surface of the cold cathode substrate 14, wherein the channel layer is selected from one or more of N-type a-Si, IGZO or IZO;

[0066] S4: preparing a bottom insulating layer 12 and a top insulating layer 8 using plasma enhanced chemical vapor deposition technology;

[0067] S5: preparing a cold cathode emitter 6 on the top grid 7;

[0068] S6: The photoelectric response layer 4 and the cold cathode emitter 6 are relatively separated by an isolator 5 and maintained in a vacuum state, wherein the thickness of the isolator is 30 to 1000 μm and the vacuum state is an air pressure ≤ 10 -2 Pa.

[0069] The step of preparing the cold cathode emitter 6 on the top grid 7 includes:

[0070] Semiconductor nanowires, which are cold cathode emitters 6, are grown on the top gate 7 using photolithography, electron beam evaporation, and thermal oxidation methods.

[0071] The cold cathode emitter uses oxide semiconductor nanowires, which have a simple preparation method and are easy to integrate with dual-gate thin-film transistors. The preparation method of oxide semiconductor nanowires is: after preparing metal on the top gate using photolithography and electron beam evaporation technology, the metal is directly heated and reacted with air to form oxide semiconductor nanowires.

[0072] In practice, the light emitted by a flat-panel photodetector includes infrared, visible, ultraviolet, X-rays, and gamma rays. When the detector is illuminated by light, the photoconductive anode, vacuum, and cold cathode emitter can be treated as a large resistor. When a forward voltage is applied to the detector's anode electrode, a forward voltage is induced on the top gate. This forward voltage on the top gate turns the N-type channel thin-film transistor on, generating a photocurrent between the source and drain electrodes.

[0073] When the detector is not illuminated by light, the resistance of the photoresponse layer of the photoconductive anode is large, the induced voltage of the top gate electrode is low, and the current between the source and drain is low, thereby achieving low dark current and high sensitivity.

[0074] Example 4

[0075] This embodiment further discloses the following contents based on Embodiments 1, 2, and 3:

[0076] like Figure 5 As shown, the difference between this embodiment and embodiment 1 is that the top gate is connected to a voltage-stabilizing diode. The remaining steps are consistent with embodiment 1. The top gate is connected to a voltage-stabilizing diode using a wire. The stable voltage of the voltage-stabilizing diode is 5 to 50V.

[0077] Example 5

[0078] This embodiment, based on Embodiments 1, 2, 3, and 4, further discloses the following contents:

[0079] In the specific implementation process, the steps for preparing a vacuum cold cathode photodetector driven by a dual-gate thin film transistor are as follows:

[0080] S1. Prepare the anode substrate: prepare a 15×15 cm 2 , a glass with a thickness of 3 mm is used as the anode substrate, an ITO electrode with a thickness of 500 nm is plated on the surface of the anode substrate using magnetron sputtering technology, and a Ga2O3 photoconductor is plated on the anode electrode as a photoelectric response layer using electron beam evaporation technology, with a coating rate of 0.8 nm / s and a thickness of 3 μm;

[0081] S2. Preparation of dual-gate thin film transistor: Prepare a 15×15cm 2 , a glass with a thickness of 3 mm is used as a cathode substrate, and Mo metal is plated on the surface of the cathode substrate by photolithography and magnetron sputtering technology as a bottom gate electrode with a thickness of 100 nm; a SiO2 film is plated on the surface of the cathode substrate plated with the bottom gate electrode as a bottom gate insulating layer with a thickness of 300 nm by plasma enhanced chemical vapor deposition PECVD technology; an IGZO film is plated on the surface of the bottom gate insulating layer as a channel layer with a thickness of 50 nm by photolithography and magnetron sputtering technology, a Cr metal layer is plated on the surface of the channel layer as a source electrode and a drain electrode with a thickness of 100 nm by photolithography and magnetron sputtering technology, SiO2 is plated on the surface of the source electrode, the drain electrode and the channel layer as a top gate insulating layer with a thickness of 200 nm by PECVD technology, and an ITO electrode is plated on the surface of the top gate insulating layer as a top gate electrode by photolithography and magnetron sputtering technology;

[0082] S3. Preparation of cold cathode emitter: ZnO nanowires were grown on the top gate electrode using a thermal oxidation method as a cold cathode emitter.

[0083] The specific preparation process of ZnO nanowires is as follows: first, a Zn metal layer is prepared on the top gate electrode by photolithography and electron beam evaporation technology, and then the sample is thermally oxidized in air to grow ZnO nanowires. The thermal oxidation temperature is 470℃ and the thermal oxidation time is 5 hours. Figure 6Shown is the surface morphology of ZnO nanowires, with a ZnO length of 100 nm and a tip diameter of approximately 20 nm;

[0084] S4. Assembling the detector: The photoelectric response layer of the photoconductive anode substrate and the cold cathode emitter of the cold cathode substrate are separated by an isolator and maintained in a vacuum state. The isolator is made of a ceramic sheet and has a thickness of 100 μm.

[0085] The preparation method of the photoconductor anode substrate is as follows: prepare a 15×15 cm 2 , a 3mm thick glass is used as the anode substrate, and an ITO electrode with a thickness of 500nm is plated on the surface of the anode substrate using magnetron sputtering technology as the anode electrode. Then, an N-type semiconductor WO3, an I-type photoconductor Ga2O3 and a P-type semiconductor NiO thin film are successively plated on the anode electrode using electron beam evaporation technology as the photoelectric response layer. The thickness of the Ga2O3 film is 3μm, and the thickness of the WO3 and NiO films are both 100nm.

[0086] Use a wire to connect the top gate to a Zener diode that has a stable voltage range of 5V.

[0087] Comparative Example 1

[0088] A vacuum cold cathode flat panel photodetector, such as Figure 7 As shown, the difference from Example 1 is that there are only cold cathode electrodes 17 and cold cathode emitters 6 on the cold cathode substrate, and the preparation method is the same as that of Example 1.

[0089] Comparative Example 2

[0090] A vacuum cold cathode flat panel photodetector driven by a single gate thin film transistor, such as Figure 8 As shown, the difference from Example 1 is that a single-gate thin film transistor is used on the cold cathode substrate, that is, the thin film transistor is composed of a bottom gate, a bottom gate insulating layer, a source electrode, and a drain electrode, and the cold cathode emitter is prepared on the drain electrode of the thin film transistor.

[0091] The test method is as follows:

[0092] The detectors described in Examples 1 to 4 and Comparative Examples 1 and 2 were placed in a vacuum chamber respectively, and a vacuum state was maintained between the anode substrate and the cold cathode substrate. The pressure of the vacuum chamber was 1×10 5Pa. The anode electrode is connected to voltage source 1, and voltage source 1 outputs a forward voltage. The drain electrode of the dual-gate thin-film transistor is connected to voltage source 2, and the source electrode is connected to an ammeter, and voltage source 2 outputs a forward voltage. The bottom gate of the dual-gate thin-film transistor is connected to voltage source 3, and voltage source 3 outputs a reverse voltage. The protection resistor of Example 3 and the voltage-stabilizing diode of Example 4 are grounded. The anode current and anode voltage characteristic curves of the detectors described in Examples 1 to 4 and Comparative Examples 1 and 2 are tested in a dark environment and under different X-ray doses, and the transfer characteristic curves of the drain current and bottom gate voltage of the dual-gate thin-film transistor are tested.

[0093] The test results are as follows, Figure 9 This is a graph showing the anode current-anode voltage curve of a vacuum cold cathode flat panel photodetector described in Example 1 under different X-ray doses. When the anode voltage is 1250V, the detector anode dark current is 1.2×10 -9 A, while the anode photocurrents at X-ray doses of 0.5 mGy / s, 1 mGy / s, 1.5 mGy / s, and 2 mGy / s were 1.26 × 10 -7 A. 1.89×10 -7 A. 2.55×10 -7 A and 3.8×10 -7 A, light-dark current ratio is 10 2 , photocurrent fluctuation is 18%, sensitivity is 1.8mCGy air -1 cm -2 , the minimum detection dose rate is 700μGy air / s, a linear dynamic range of 40dB, and a rising edge response time of 100ms. Furthermore, the detector's anode breakdown voltage is 1800V. These results demonstrate that vacuum cold cathode photodetectors can achieve high-sensitivity detection by utilizing the photomultiplication mechanism of the electron bombardment-induced photoconductivity effect. However, they still suffer from issues such as large dark current, large photocurrent fluctuations, a high minimum detection dose, a small linear dynamic range, and slow response speed.

[0094] When the anode voltage of the vacuum cold cathode flat-panel photodetector driven by a single-gate thin-film transistor described in Comparative Example 2 is 1250 V, the dark current of the detector transistor channel is 1.1×10 -9 A, while the photocurrents of the transistor channel when the X-ray dose is 0.5mGy / s, 1mGy / s, 1.5mGy / s and 2mGy / s are 1.15×10 -7 A. 1.76×10 -7 A. 2.36×10 -7 A and 3.29×10 -7 A, light-dark current ratio is 10 2, photocurrent fluctuation is 9% and sensitivity is 1.6mCGy air -1 cm -2 , the minimum detection dose rate is 700μGy air / s, a linear dynamic range of 40dB, and a rising edge response time of 90ms. Furthermore, the detector's anode breakdown voltage is 1800V. These results demonstrate that thin-film transistor-driven vacuum cold cathode flat-panel photodetectors can reduce photocurrent fluctuations by utilizing the current-limiting effect of thin-film transistors in the saturation region. However, they still present challenges such as large dark current, a high minimum detection dose, a small linear dynamic range, and slow response speed.

[0095] Figure 10 1 is a transfer characteristic curve of the source current and bottom gate voltage of the dual-gate transistor when the anode voltage of the detector of Example 1 is 1250V. Figure 11 The relationship between the threshold voltage and X-ray dose of the corresponding dual-gate thin-film transistor is shown in Figure 2. The results show that the threshold voltage of the dual-gate thin-film transistor decreases linearly with the increase of the irradiated X-ray dose, thus producing a photocurrent amplification effect. When the bottom gate voltage is adjusted to -4V, the dark current is 6.3×10 -15 A, corresponding to an X-ray dose of 0.5 mGy air / s, 1mGy air / s, 1.5mGy air / s and 2mGy air The photocurrents at the time points are 3.18×10 -16 A. 4.34×10 -12 A. 7.02×10 -10 A. 1.56×10 -8 A. 1.72×10 -7 A, corresponding to a maximum light-dark current ratio of 10 8 , photocurrent fluctuation is 5%, sensitivity is 3.5mCGy air -1 cm -2 , the minimum detection dose rate is 300μGy air / s, a linear dynamic range of 90dB, and a rising edge response time of 100ms. Furthermore, the detector's anode breakdown voltage is 1800V. These results demonstrate that under X-ray irradiation, the threshold voltage of the dual-gate thin-film transistor decreases, generating a photocurrent amplification effect, enabling low dark current, high photocurrent, and high-sensitivity X-ray detection. Furthermore, the dual-gate thin-film transistor utilizes the current-limiting effect in the saturation region to achieve low current fluctuations, and utilizes the low dark current in the cutoff region to achieve low detection dose and a high linear dynamic range.

[0096] In the specific implementation process, the vacuum cold cathode detector driven by the dual-gate thin film transistor based on the PIN type photoelectric response layer described in Example 2 has a dark current between the source and drain of the thin film transistor of 2.7×10 -15 A, the photocurrent at an X-ray dose of 2 mGy / s is 1.9×10 -6 A, the maximum light-dark current ratio is 10 9 , photocurrent fluctuation is 5%, sensitivity is 16mCGy air -1 cm -2 , the minimum detection dose rate is 100μGy air / s, a linear dynamic range of 95dB, and a rising edge response time of 20ms. Furthermore, the detector's anode breakdown voltage is 1900V. These results demonstrate that utilizing a PIN-type photoresponse layer can increase the thickness of the photoconductor depletion layer, thereby improving light absorption efficiency; increase the photoconductor's operating electric field, thereby improving the efficiency of photogenerated carrier collection; and utilize the impact ionization effect under high electric fields to achieve an avalanche photomultiplication mechanism, thereby increasing detector sensitivity; reduce the detector's dark current, thereby improving the linear dynamic range and reducing the detection dose; and utilize the drift current of the depletion layer to achieve a fast photoresponse.

[0097] In the specific implementation process, the difference between Example 3 and Example 1 is that a protection resistor connected to the top gate is added. When the anode voltage of the vacuum cold cathode flat-panel photodetector driven by the dual-gate thin film transistor in Example 3 is 1250V, the dark current between the source and drain of the transistor is 2.5×10 -15 A, the photocurrent when the X-ray dose is 2 mGy / s is 6.1×10 -7 A, corresponding to a sensitivity of 4.9mCGy air -1 cm -2 , the light-to-dark current ratio is on the order of 10 8 , photocurrent fluctuation is 5%, the minimum detection dose rate is 220μGy air / s, a linear dynamic range of 92dB, and a rising edge response time of 100ms. Furthermore, the detector's anode breakdown voltage is 2500V. The primary function of the protection resistor is to divide the top gate voltage applied to the device into two parts: the top gate insulation layer and the protection resistor, thereby improving the device's high-voltage resistance through voltage division. These results demonstrate that the protection resistor can increase the breakdown voltage of vacuum cold cathode flat-panel photodetectors driven by dual-gate thin-film transistors, facilitating the regulation of the detector's anode voltage and photoelectric response characteristics.

[0098] In the specific implementation process, the difference between Example 4 and Example 1 is that a voltage stabilizing diode connected to the top gate is added. When the anode voltage of the vacuum cold cathode detector driven by the dual-gate thin film transistor in Example 4 is 1250V, the dark current between the source and drain of the transistor is 3.7×10 -15 A, the photocurrent when the X-ray dose is 2 mGy / s is 5.7×10 -7 A, corresponding to a sensitivity of 2.9 mCGy air -1 cm -2 , the light-to-dark current ratio is on the order of 10 8 , photocurrent fluctuation is 5%, the minimum detection dose rate is 240μGy air / s, a linear dynamic range of 93dB, and a rising edge response time of 100ms. Furthermore, the detector's anode breakdown voltage is 3200V. The working principle of a Zener diode is similar to that of a protective resistor. This result suggests that a Zener diode can increase the breakdown voltage of a vacuum cold cathode flat-panel photodetector driven by a dual-gate thin-film transistor, facilitating the regulation of the detector's anode voltage and photoelectric response characteristics.

[0099] The same or similar reference numerals correspond to the same or similar components;

[0100] The terms used in the drawings to describe positional relationships are for illustrative purposes only and should not be construed as limiting this patent;

[0101] Obviously, the above embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. A vacuum cold cathode flat-panel photodetector driven by a dual-gate thin-film transistor, characterized in that: It includes a photoconductive anode substrate, a cold cathode substrate driven by a dual-gate thin film transistor, and an isolator (5). The photoconductive anode substrate comprises an anode substrate (2), an anode electrode (3) and a photoelectric response layer (4), wherein the anode electrode (3) is arranged on the surface of the anode substrate (2), and the photoelectric response layer (4) is arranged on the anode electrode (3); the cold cathode substrate comprises a cold cathode emitter (6), a top grid electrode (7), a top insulating layer (8), a source electrode (9), a drain electrode (10), a channel layer (11), a bottom insulating layer (12), a bottom grid electrode (13) and a cold cathode substrate (14), wherein the bottom grid electrode (13) is arranged on the cold cathode substrate (14), and the bottom insulating layer (8) is arranged on the cold cathode substrate (14). The insulating layer (12) is arranged on the bottom gate (13), the channel layer (11) is arranged on the bottom insulating layer (12), the source electrode (9) and the drain electrode (10) are separated by the channel layer (11), the top insulating layer (8) is arranged on the channel layer (11), the top gate (7) is arranged on the top insulating layer (8), the cold cathode emitter (6) is arranged on the top gate (7), the photoconductive anode substrate and the cold cathode substrate are separated by an insulator (5), and a vacuum state is formed between the photoelectric response layer (4) and the cold cathode emitter (6).

2. The dual-gate thin film transistor driven vacuum cold cathode flat panel photodetector according to claim 1, characterized in that: The photoelectric response layer (4) comprises one or more photoconductors selected from Ga2O3, AlGaN, GaN, GaAs, a-Se, CdTe, perovskite and HgI2.

3. The dual-gate thin film transistor driven vacuum cold cathode flat panel photodetector according to claim 1, characterized in that: The photoelectric response layer (4) further comprises a P-type semiconductor (17) of a PIN structure, an I-type photoconductor (16), and an N-type semiconductor (15), wherein the N-type semiconductor (15) is arranged on the anode electrode (3), the I-type photoconductor (16) is arranged on the N-type semiconductor (15), and the P-type semiconductor (17) is arranged on the I-type photoconductor (16).

4. The dual-gate thin film transistor driven vacuum cold cathode flat panel photodetector according to claim 3, characterized in that: The P-type semiconductor (17) includes any one of P-type NiO, Cu2O, CoO, Cu2S, SnO, SnS and MnO semiconductors.

5. The dual-gate thin film transistor driven vacuum cold cathode flat panel photodetector according to claim 4, characterized in that: The I-type photoconductor (16) includes any one of I-type Ga2O3, AlGaN, GaN, GaAs, a-Se, CdTe, perovskite and HgI2 photoconductors.

6. The dual-gate thin film transistor driven vacuum cold cathode flat panel photodetector according to claim 4, characterized in that: The N-type semiconductor (15) includes any one of N-type WO3, TiO2, Fe2O3, ZnO, V2O5, CrO3 and BaO semiconductors.

7. The dual-gate thin film transistor driven vacuum cold cathode flat panel photodetector according to claim 1, characterized in that: The cold cathode emitter (6) comprises a semiconductor nanowire formed by any one of zinc oxide, copper oxide, tungsten oxide, iron oxide and molybdenum oxide.

8. The dual-gate thin film transistor driven vacuum cold cathode flat panel photodetector according to any one of claims 1 to 7, characterized in that: The top gate (7) is connected to a protection resistor or a voltage stabilizing diode, and the resistance range of the protection resistor is 10 2 ~10 12 Ω, the stable voltage range of the voltage stabilizing diode is 5 to 50V.

9. A method for preparing a vacuum cold cathode flat-panel photodetector driven by a dual-gate thin film transistor, characterized in that: The preparation method is applied to the vacuum cold cathode flat-panel photodetector according to any one of claims 1 to 8, comprising the following steps: S1: preparing an anode electrode (3) on the surface of an anode substrate (2) using magnetron sputtering technology; S2: using electron beam evaporation technology to prepare a photoelectric response layer (4) on the prepared anode electrode (3); S3: using magnetron sputtering, photolithography and wet etching techniques to prepare a bottom gate (13), a channel layer (11), a source electrode (9), a drain electrode (10) and a top gate (7) on the surface of a cold cathode substrate (14); S4: preparing a bottom insulating layer (12) and a top insulating layer (8) using plasma enhanced chemical vapor deposition technology; S5: preparing a cold cathode emitter (6) on the top grid (7); S6: The photoelectric response layer (4) and the cold cathode emitter (6) are relatively separated by an isolator (5) and maintained in a vacuum state.

10. The preparation method according to claim 9, characterized in that In step S5, the cold cathode emitter (6) is prepared on the top grid (7), comprising: Photolithography, electron beam evaporation and thermal oxidation methods are used to grow semiconductor nanowires on the top gate (7), which are cold cathode emitters (6).

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