CN111081809B - High-sensitivity X-ray detector - Google Patents
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- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/08—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof in which radiation controls flow of current through the device, e.g. photoresistors
- H01L31/10—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof in which radiation controls flow of current through the device, e.g. photoresistors characterised by at least one potential-jump barrier or surface barrier, e.g. phototransistors
- H01L31/115—Devices sensitive to very short wavelength, e.g. X-rays, gamma-rays or corpuscular radiation
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/18—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
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Abstract
The invention discloses a high-sensitivity X-ray detector which comprises an X-ray detection component and a cold cathode vacuum diode, wherein the X-ray detection component comprises a photoconductor, a first anode electrode and a first cathode electrode which are arranged on two sides of the photoconductor, the thickness of the photoconductor is 0.1-5000 mu m, and the X-ray detection component is connected with the cold cathode vacuum diode in series. The invention arranges the photoconductor on the X-ray detection element, and avoids the electrons emitted by the cold cathode emitter from directly bombarding the photoconductor, thereby improving the working voltage and sensitivity of the X-ray detector.
Description
Technical Field
The present invention relates to the field of X-ray detectors, and more particularly, to a high-sensitivity X-ray detector.
Background
The X-ray detector has wide application in the fields of medical diagnosis, safety inspection, industrial nondestructive testing, nuclear power stations, environmental radioactivity detection, scientific research and the like. In an X-ray detector, the sensitivity increases with increasing voltage. For example, Pan et al prepared a perovskite X-ray detector and found a detection sensitivity of 8 μ CGy at a bias of 1Vair -1cm-2And a sensitivity of 105 μ CGy at 50V biasair -1cm-2(W.Pan, et al, Nature Photonics,11,726 (2017)). However, as the voltage increases, the detector is prone to generate phenomena such as large dark current, unstable current, and current breakdown due to heat generation, thereby limiting further improvement of the sensitivity of the device.
Disclosure of Invention
In order to overcome at least one of the defects in the prior art, the invention provides the high-sensitivity X-ray detector, which can improve the working voltage of the detector and improve the photocurrent under high voltage.
The invention adopts the following technical scheme to solve the problems in the prior art:
a high-sensitivity X-ray detector comprises an X-ray detection component and a cold cathode vacuum diode, wherein the cold cathode vacuum diode comprises an anode substrate and a cathode substrate; the anode substrate comprises an anode substrate and a second anode electrode, and the second anode electrode is arranged on the anode substrate; the cathode substrate comprises a cathode substrate, a second cathode electrode and a nanowire cold cathode emitter, wherein the second cathode electrode is arranged on the cathode substrate, and the nanowire cold cathode emitter is arranged on the second cathode electrode; the cathode substrate and the anode substrate are fixed together in an insulated manner through an isolator; the second anode electrode and the nanowire cold cathode emitter are oppositely arranged, a vacuum gap is kept between the anode substrate and the cathode substrate, the X-ray detection component comprises the photoconductor, a first anode electrode and a first cathode electrode which are arranged on two sides of the photoconductor, the thickness of the photoconductor is 0.1-5000 microns, and the X-ray detection component is connected with the cold cathode vacuum diode in series.
The thickness of the photoconductor is 0.1-5000 μm. The thickness of the photoconductor is less than 0.1 μm, and the absorption of X-rays is insufficient; the thickness of the photoconductor is more than 5000 μm, the light signal is difficult to collect, and the detection sensitivity is low.
The vacuum gap of the cold cathode vacuum diode is utilized to effectively reduce the dark current of the X-ray detector, improve the working voltage of the detector and realize larger photocurrent under high voltage, thereby realizing high-sensitivity detection.
On one hand, the dark current of the X-ray detector is effectively reduced by utilizing the vacuum gap of the cold cathode vacuum diode; on the other hand, the photoconductor of the X-ray detector can generate current fluctuation and current breakdown under high voltage, and because the cold cathode vacuum diode has a vacuum gap and large equivalent resistance, when the cold cathode vacuum diode works under high voltage, the suddenly increased current can be adjusted to return to a normal value by the equivalent high resistance of the cold cathode vacuum diode, so that the current fluctuation and the current breakdown of the X-ray detector are prevented, the current self-adjusting function is achieved, and the detector is prevented from being damaged under high current.
The principle is as follows: a photoconductor is used to convert the X-rays into electrical signals, which are then read out by a cold cathode vacuum diode. The photoconductor is integrated on an X-ray detection component, so that electrons emitted by a cold cathode emitter are prevented from directly bombarding the photoconductor, and the photoconductor is prevented from being damaged.
Furthermore, the mode that the X-ray detection component and the cold cathode vacuum diode are connected in series is that an anode electrode of the X-ray detection component is connected with a voltage source, a cathode electrode of the X-ray detection component is connected with an anode electrode of the cold cathode vacuum diode, and a cathode electrode of the cold cathode vacuum diode is connected with an ammeter.
Furthermore, the mode that the X-ray detection component and the cold cathode vacuum diode are connected in series is that the anode electrode of the cold cathode vacuum diode is connected with a voltage source, the cathode electrode of the cold cathode vacuum diode is connected in series with the anode electrode of the X-ray detection component, and the cathode electrode of the X-ray detection component is connected with an ammeter.
Further, the photoconductor is a high atomic number photoconductor or a wide bandgap photoconductor or an avalanche photoconductor.
The photoconductor generates electron-hole pairs under the irradiation of X-rays, has low generation energy of the electron-hole pairs, and is a good detection photoconductor. The cold cathode vacuum diode can improve the working voltage of the X-ray detector, and the electron-hole pairs obtain higher energy under high voltage and collide and ionize with crystal lattices of the photoconductor to generate an avalanche effect, so that the photocurrent and the sensitivity of the detector are greatly improved. The photoconductor is a-Se, CdTe, HgI2、PbI2PbO, perovskite, Ga2O3Or a combination of two or more of them.
Further, a P-N junction structure prepared on the photoconductor is also included. When a depletion layer between the P-N junctions is irradiated by X-rays, electron hole pairs are generated, under the action of high reverse voltage, photo-generated carriers obtain high energy, and the photo-generated carriers collide with crystal lattices to be ionized to generate an avalanche effect, so that the photocurrent is greatly increased, and the high-sensitivity X-ray detector is obtained.
Further, the P-N junction structure comprises P-Si/N-Ga2O3、p-Se/n-CdO、p-CdTe/n-CdS、p-PbO/n-PbO、p-Si/n-Ga2O3. The Fermi level of the P-type semiconductor is close to the top of the valence band, the Fermi level of the N-type semiconductor is close to the conduction band and is low, and any two P-type semiconductors and N-type semiconductors can form PN junctions as long as the preparation process is mature.
Furthermore, in the P-N junction structure, the first anode electrode is prepared on one side of the N-type semiconductor, and the first cathode electrode is prepared on one side of the P-type semiconductor. The PN direction is forward biased and the NP direction is reverse biased. Only the reverse bias can bear larger voltage, and the avalanche effect is realized.
Further, the nanowire cold cathode emitter is a zinc oxide nanowire, a copper oxide nanowire, a tungsten oxide nanowire, a molybdenum oxide nanowire, an iron oxide nanowire, a titanium oxide nanowire or a tin oxide nanowire. The nanowire cold cathode can realize large-area preparation, and the nanowire is a semiconductor nanowire capable of stably emitting electrons.
Further, the height of the separator is 50-1000 μm.
Further, the vacuum degree of the vacuum gap is 10-7～10-3Pa。
The invention can be used in the non-imaging field, such as the environmental monitoring near a nuclear power station, and the detector is used for detecting whether the surrounding environment contains X rays, the higher the sensitivity is, the better the sensitivity is, and the damage of the X rays to the human body can be effectively prevented.
Compared with the prior art, the invention has the beneficial effects that:
under high voltage, the voltage drops on the cold cathode vacuum diode quickly, the invention arranges the photoconductor on the X-ray detection element, and avoids the electrons emitted by the cold cathode emitter from directly bombarding the photoconductor.
According to the high-sensitivity X-ray detector, the cold cathode vacuum diode and the X-ray detection component are connected in series, the dark current of the X-ray detector is effectively reduced by utilizing the vacuum gap of the cold cathode vacuum diode, the current fluctuation and the current breakdown of the component are effectively prevented, and a large photocurrent can be realized at high voltage, so that the working voltage and the sensitivity of the X-ray detector are improved.
In addition, the cold cathode vacuum diode can bear larger working voltage and can generate self-regulation effect on the current of the detector, when the avalanche effect occurs, the voltage quickly drops on the cold cathode vacuum diode, electrons emitted by the cold cathode emitter are prevented from directly bombarding the photoconductor, the device is prevented from being damaged, and therefore the avalanche multiplication effect under high voltage is effectively utilized to realize high-sensitivity detection.
Drawings
FIG. 1 is a schematic diagram of an X-ray detector configuration and circuitry;
FIG. 2 is a surface topography of a ZnO nanowire cold cathode emitter;
FIG. 3 shows HgI2Voltage current curve of the photoconductor under dark environment and X-ray irradiation;
FIG. 4 shows HgI2A voltage current curve of an X-ray detector with a photoconductor connected with a ZnO nanowire cold cathode vacuum diode in series under the irradiation of X-rays in a dark environment;
FIG. 5 shows Ga2O3Voltage current curve of the photoconductor under dark environment and X-ray irradiation;
FIG. 6 shows Ga2O3And voltage and current curves of an X-ray detector with a photoconductor and a ZnO nanowire cold cathode vacuum diode connected in series under dark environment and X-ray irradiation.
FIG. 7 is a schematic diagram of an integrated photoconductor and cold cathode X-ray detector configuration;
description of the reference numerals
A first anode electrode 1; a photoconductor 2; x-ray 3; a first cathode electrode 4; an anode substrate 5; a second anode electrode 6; a spacer 7; a nanowire cold cathode emitter 8; a second cathode electrode 9; a cathode substrate 10; comparative example anode substrate 11; comparative example anode electrode 12; comparative example photoconductor 13; comparative example separator 14; comparative example gate electrode stripes 15; a comparative example insulating layer 16; comparative example cathode electrode strip 17; comparative example cathode substrate 18; comparative example a cold cathode emitter 19.
Detailed Description
The present invention will be further described with reference to the following embodiments.
Example 1
This embodiment uses specific examples to describe in detail the detailed preparation process of the high-sensitivity X-ray detector according to the present invention. Figure 1 is a schematic diagram of the structure and circuitry of a high sensitivity X-ray detector,
the X-ray detector with high sensitivity comprises an X-ray detection component and a cold cathode vacuum diode, wherein the X-ray detection component comprises a photoconductor 2, a first anode electrode 1 and a first cathode electrode 4 which are arranged on two sides of the photoconductor, the thickness of the photoconductor is 0.1 mu m, and the X-ray detection component is connected with the cold cathode vacuum diode in series.
The cold cathode vacuum diode comprises an anode substrate and a cathode substrate; the anode substrate comprises an anode substrate 5 and a second anode electrode 6, wherein the second anode electrode 6 is arranged on the anode substrate 5; the cathode substrate comprises a cathode substrate 10, a second cathode electrode 9 and a nanowire cold cathode emitter 8, wherein the second cathode electrode 9 is arranged on the cathode substrate 5, and the nanowire cold cathode emitter 8 is arranged on the second cathode electrode 9; the cathode substrate and the anode substrate are fixed together through a separator 7 in an insulated manner; the second anode electrode 9 is arranged opposite to the nanowire cold cathode emitter 8, a vacuum gap is kept between the anode substrate and the cathode substrate, and the height of the separator 7 is 500 μm.
The vacuum degree of the vacuum gap is 10-5Pa。
The preparation process comprises the following steps:
(1) and preparing an X-ray detection component. Preparing monocrystal HgI from KI water solution by adopting temperature difference method2The photoconductor 2 of (1), the KI aqueous solution has a concentration of 0.1mol/L, and the temperatures of the dissolution zone and the growth zone are 65 ℃ and 60 ℃, respectively. Single crystal HgI with a thickness of 0.1 μm was obtained by cutting2The photoconductor 2 of (1). By magnetron sputtering method in HgI2The first anode electrode 1 and the first cathode electrode 4 are prepared on two sides of the photoconductor 2, the material of the first anode electrode 1 and the first cathode electrode 4 is ITO, the effective area of the electrodes is 3.14mm2The coating power is 1.2KW, the coating speed is 14nm/min, and the thickness is 200 nm.
(2) And preparing an anode substrate of the cold cathode vacuum diode. A glass anode substrate 5 having an area of 12.5cm by 9.5cm and a thickness of 3mm was prepared. And (3) plating an ITO electrode on the surface of the glass substrate by using a magnetron sputtering technology to serve as a second anode electrode 6, wherein the plating power is 1.2KW, the plating speed is 14nm/min, and the thickness of the ITO electrode is 500 nm.
(3) And preparing a cathode substrate of the cold cathode vacuum diode. A cathode substrate 10 having an area of 12.5cm × 9.5cm and a thickness of 3mm was prepared, and the material of the cathode substrate 10 was glass. And (3) plating an ITO electrode on the surface of the glass substrate by using a magnetron sputtering technology to serve as a second cathode electrode 9, wherein the plating power is 1.2KW, the plating speed is 14nm/min, and the thickness of the second cathode electrode 9 is 500 nm. Growing a ZnO nanowire cold cathode emitter 8 on the second cathode electrode 9 by adopting a thermal oxidation method, wherein the effective area of the cold cathode emitter is 3.672cm2. The specific preparation process of the ZnO nanowire is as follows: firstly, preparing a Zn lattice on a cathode electrode through photoetching and electron beam evaporation, and then heating the Zn lattice in the atmosphere to grow the ZnO nanowire at the growth temperature of 500 ℃ for 3 hours. FIG. 2 is a morphology diagram of a ZnO nanowire cold cathode. The growth density of ZnO nanowire is about 4 × 108cm-2The height is about 2 to 3 μm and the tip diameter is about 20 nm.
(4) And preparing the cold cathode vacuum diode. The side of the anode substrate provided with the second anode electrode 6 and the side of the cathode substrate provided with the cold cathode emitter 8 are fixed to each other in an insulated manner by a separator 7. The spacer 7 is made of a ceramic sheet and has a height of 500 μm. Then, the device was placed in a vacuum chamber or vacuum-sealed, and a vacuum gap was maintained between the anode substrate and the cathode substrate at a vacuum degree of 10-5Pa。
(5) The X-ray detection component and the cold cathode vacuum diode are connected in series. The first cathode electrode 4 is connected with the second anode electrode 6 through a leading-out wire.
(6) The first anode electrode 1 is connected with an outgoing lead wire to be connected with an external voltage source, and the second cathode electrode 9 is connected with an outgoing lead wire to be connected with an ammeter.
In this embodiment, step (1) is first implemented, and then the first anode electrode 1 is connected to the external voltage source via the outgoing line, and the first anode electrode 1 is connected to the ammeter via the outgoing line. FIG. 3 shows the current-voltage curve of the device under dark conditions and under X-ray 3 irradiation at an X-ray dose of 2.8mGyairAnd s. The maximum voltage of the device is 130V, and the dark current under the voltage of 130V is 1.3 multiplied by 10-8A, and the photocurrent was 2.9X 10-7A. The calculated sensitivity of the device was 3.1 × 103μCGyair -1cm-2。
In this example, the steps (1) to (6) are continued, and a current-voltage curve of the device under dark environment and under irradiation of the X-ray 3 is obtained as shown in fig. 4. The maximum voltage of the device is 1200V, and the dark current under the voltage of 1200V is 6.4 multiplied by 10-8A, and the photocurrent was 6.7X 10-7A. The calculated sensitivity of the device was 6.8 × 103μCGyair -1cm-2. This phenomenon demonstrates that when an X-ray detection device is connected in series with a cold cathode vacuum diode, the operating voltage of the device can be increased, thereby increasing the photocurrent and detection sensitivity of the device.
Example 2
The difference between this embodiment and embodiment 1 lies in the difference of the step (1) for preparing the X-ray detection device, and the other steps are the same as those in embodiment 1. The specific preparation process of the X-ray detection component comprises the following steps: production of single crystal Ga on sapphire substrate using Metal Organic Chemical Vapor Deposition (MOCVD) system2O3The photoconductor 2, the precursor is triethyl gallium and high-purity oxygen, the transport gas is argon, the growth pressure is 9.1Torr, the growth temperature is within 500 ℃, and Ga2O3The photoconductor had an effective area of 2 inches and a thickness of 2500 μm. Then using magnetron sputtering technique to form Ga2O3Two surfaces of photoconductorPreparing a first anode electrode 1 and a first cathode electrode 4 at the ends, wherein the first anode electrode 1 and the first cathode electrode 4 are made of Au, the plating rate is 30nm/min, the thickness of the Au electrode is 150nm, and the effective area between the two electrodes is 2 multiplied by 0.3cm2。
In this embodiment, step (1) is first implemented, and then the first anode electrode 1 is connected to the external voltage source via the outgoing line, and the first anode electrode 1 is connected to the ammeter via the outgoing line. Fig. 5 shows the current-voltage curve of the device in dark conditions and under X-ray 3 irradiation. The maximum voltage of the device is 200V, and the dark current under the voltage of 200V is 4.3 multiplied by 10-10A, and the photocurrent was 7.9X 10-8A. The sensitivity of the device was calculated to be 66 μ CGyair -1cm-2。
In this example, the steps (1) to (6) are continued, and a current-voltage curve of the device under dark environment and under irradiation of the X-ray 3 is obtained as shown in fig. 6. The maximum voltage of the device is 2500V, and the dark current under the voltage of 2500V is 9.3 multiplied by 10-9A, and the photocurrent was 6.6X 10-7A. The calculated sensitivity of the device was 8.8 × 102μCGyair -1cm-2. This phenomenon demonstrates that when an X-ray detection device is connected in series with a cold cathode vacuum diode, the operating voltage of the device can be increased, thereby increasing the photocurrent and detection sensitivity of the device.
Example 3
The difference between this embodiment and embodiment 1 lies in the difference of the step (1) for preparing the X-ray detection device, and the other steps are the same as those in embodiment 1. The specific preparation process of the X-ray detection component comprises the following steps: preparing Ga on p-type silicon substrate by using vacuum coating equipment such as electron beam evaporation or magnetron sputtering2O3Photoconductor 2, Ga2O3Has an effective area of 1X 1cm2With a thickness of 5000 μm, to obtain a crystalline silicon film composed of p-Si and Ga2O3A photoconductor 2 composed of a photoconductor. Then using magnetron sputtering technique to form Ga2O3Preparing a Ti/Au first anode electrode 1 with the thickness of 100nm on the surface of a photoconductor, and preparing an Au first anode electrode with the thickness of 100nm on the back of a p-type silicon substrate by using a magnetron sputtering technologyAnd a cathode electrode 4.
In this embodiment, the steps (1) to (6) are continuously performed to obtain current and voltage data of the device in a dark environment and under irradiation of the X-ray 3. The device obtains the maximum voltage of 2900V and the dark current under the voltage of 2900V is 8.2 multiplied by 10-11A, and the photocurrent was 7.3X 10-6A. The calculated sensitivity of the device was 7.6 × 103μCGyair -1cm-2. This phenomenon illustrates that the heterojunction formed on the photoconductor can achieve avalanche gain at high voltage. I.e. p-Si and Ga2O3When a depletion layer between photoconductors is irradiated by X-rays, electron-hole pairs are generated, under the action of high reverse voltage, photo-generated carriers obtain high energy, and the photo-generated carriers collide with crystal lattices to be ionized, so that an avalanche effect is generated, and the photocurrent is greatly increased.
Comparative example 1
This comparative example illustrates an X-ray detector integrating a photoconductor and a cold cathode emitter in detail with a specific example. As shown in FIG. 7, the X-ray detector of this comparative example was composed of a comparative example photoconductor 13, an anode substrate and a cold cathode substrate, and the device effective area was 1.28X 0.96cm2。
The photoconductive anode substrate was composed of a comparative example anode substrate 11, a comparative example anode electrode 12, and a comparative example photoconductor 13. Comparative example the material of the anode substrate 11 was glass. Firstly, preparing a comparative example anode electrode 12 on an anode glass substrate by adopting a magnetron sputtering method, wherein the comparative example anode electrode 12 is made of ITO and has the thickness of 500 nm; then, a comparative example photoconductor 13 was prepared on the comparative example anode electrode 12 by using a physical vapor deposition technique, and the material of the comparative example photoconductor 13 was amorphous selenium having a thickness of 1 mm.
The cold cathode substrate is an addressable Spindt-type cold cathode substrate, comprising a comparative example cathode substrate 18, a comparative example cathode electrode strip 17, a comparative example gate electrode strip 15, a comparative example cold cathode emitter 19 and a comparative example insulating layer 16 prepared between the comparative example cathode electrode strip 17 and the comparative example gate electrode strip 15. The comparative cathode electrode strips 17 are directly prepared on the comparative cathode substrate 18, and the comparative cathode substrate 18 is made of a silicon wafer and is mutually crossed and vertically distributed with the comparative gate electrode strips 15. Comparative example cold cathode emitter 19 is a metallic molybdenum tip cone prepared on top of comparative example gate electrode stripe 15.
The photoconductive anode substrate with comparative example photoconductor 13 described above has one side facing the cold cathode substrate with one side of the comparative cold cathode emitter 19, and is held together in an insulated manner by the comparative example spacer 14. Maintaining vacuum gap state between the photoconductive anode substrate and the cold cathode substrate, wherein the vacuum degree is maintained at 1 × 10-5Pa. The comparative anode electrode 12 of the photoconductive anode and the comparative grid electrode strip 15 of the cold cathode substrate were then wired to an external power supply and the comparative cathode electrode strip 17 of the cold cathode substrate was wired to ground. The present comparative example can perform the function of address imaging by row-column scanning of the comparative cathode electrode stripes 17 and the comparative gate electrode stripes 15 of the cold cathode substrate.
In this comparative example, the X-ray response procedure was: (1) when the comparative example photoconductor 13 is irradiated with X-rays, the comparative example photoconductor 13 generates electron-hole pairs; (2) under the action of a high electric field, the holes drift and move to impact other atoms to generate collision ionization, so that an avalanche effect is generated, and multiplied holes are obtained; (3) the multiplied holes are read and output by the electron beam emitted from the comparative example cold cathode emitter 19. Based on the principle, the comparative example can realize a high-sensitivity X-ray imaging device by utilizing the avalanche effect of the a-Se photoconductor, and the avalanche gain can reach 200.
However, this comparative example still has several technical drawbacks: (1) electrons emitted by the cold cathode emitter can directly bombard the photoconductor, damage the photoconductor and cause current breakdown of the photoconductor; (2) the preparation process of the Spindt type cold cathode is complex, so that the practical application of the device is limited; (3) conventional photoconductors such as amorphous selenium have low absorption of high-energy X-rays and are not suitable for detection of high-energy X-rays.
Comparative example 2
The present embodiment is different from embodiment 2 in the thickness of the photoconductor, and the other steps are the same as embodiment 1. The specific preparation process of the X-ray detection component comprises the following steps: production of single crystal Ga on sapphire substrate using Metal Organic Chemical Vapor Deposition (MOCVD) system2O3The photoconductor 2, the precursor is triethyl gallium and high-purity oxygen, the transport gas is argon, the growth pressure is 9.1Torr, the growth temperature is within 500 ℃, and Ga2O3The photoconductor had an effective area of 2 inches and a thickness of 0.01 μm. Then using magnetron sputtering technique to form Ga2O3Preparing a first anode electrode 1 and a first cathode electrode 4 at two ends of the surface of a photoconductor, wherein the first anode electrode 1 and the first cathode electrode 4 are made of Au, the plating rate is 30nm/min, the thickness of the Au electrode is 150nm, and the effective area between the two end electrodes is 2 multiplied by 0.3cm2。
In this example, steps (1) to (6) were continued. The maximum voltage of the device is 900V, and the dark current under the voltage of 900V is 1.1 multiplied by 10-8A, and the photocurrent was 1.4X 10-7A. The sensitivity of the device was calculated to be 4 μ CGyair -1cm-2. Compared with example 2, it is demonstrated that the thickness of the photoconductor is less than 0.1 μm, and the absorption of X-rays is insufficient, resulting in lower X-ray detection sensitivity.
Comparative example 3
The present embodiment is different from embodiment 2 in the thickness of the photoconductor, and the other steps are the same as embodiment 1. The specific preparation process of the X-ray detection component comprises the following steps: production of single crystal Ga on sapphire substrate using Metal Organic Chemical Vapor Deposition (MOCVD) system2O3The photoconductor 2, the precursor is triethyl gallium and high-purity oxygen, the transport gas is argon, the growth pressure is 9.1Torr, the growth temperature is within 500 ℃, and Ga2O3The photoconductor had an effective area of 2 inches and a thickness of 5500 μm. Then using magnetron sputtering technique to form Ga2O3Preparing a first anode electrode 1 and a first cathode electrode 4 at two ends of the surface of a photoconductor, wherein the first anode electrode 1 and the first cathode electrode 4 are made of Au, the plating rate is 30nm/min, the thickness of the Au electrode is 150nm, and the effective area between the two end electrodes is 2 multiplied by 0.3cm2。
In this example, steps (1) to (6) were continued. The maximum voltage obtained by the device is 2500V, 2Dark current at 500V was 2.8X 10-9A, and the photocurrent was 6.4X 10-9A. The sensitivity of the device was calculated to be 4.8 μ CGyair -1cm-2. In principle, the maximum voltage that an X-ray detector can withstand is related to the thickness of the photoconductor and the cold cathode vacuum diode. However, the thickness of the photoconductor increases, which also causes difficulty in collecting optical signals and low sensitivity.
Compared with example 2, it is demonstrated that the thickness of the photoconductor is more than 5000 μm, and the optical signal is difficult to collect, resulting in low detector sensitivity.
It should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.
Claims (10)
1. A high-sensitivity X-ray detector comprises an X-ray detection component and a cold cathode vacuum diode,
the cold cathode vacuum diode comprises an anode substrate and a cathode substrate; the anode substrate comprises an anode substrate and a second anode electrode, and the second anode electrode is arranged on the anode substrate; the cathode substrate comprises a cathode substrate, a second cathode electrode and a nanowire cold cathode emitter, wherein the second cathode electrode is arranged on the cathode substrate, and the nanowire cold cathode emitter is arranged on the second cathode electrode; the cathode substrate and the anode substrate are fixed together in an insulated manner through an isolator; the second anode electrode is arranged opposite to the nanowire cold cathode emitter, a vacuum gap is kept between the anode substrate and the cathode substrate,
the X-ray detection component comprises a photoconductor, a first anode electrode and a first cathode electrode which are arranged on two sides of the photoconductor, the thickness of the photoconductor is 0.1-5000 mu m, and the X-ray detection component is connected with the cold cathode vacuum diode in series.
2. The high-sensitivity X-ray detector according to claim 1, wherein the X-ray detection component and the cold cathode vacuum diode are connected in series in such a manner that an anode electrode of the X-ray detection component is connected to a voltage source, a cathode electrode of the X-ray detection component is connected to an anode electrode of the cold cathode vacuum diode, and a cathode electrode of the cold cathode vacuum diode is connected to an ammeter.
3. The high-sensitivity X-ray detector according to claim 1, wherein the X-ray detection component is connected in series with the cold cathode vacuum diode in such a manner that an anode electrode of the cold cathode vacuum diode is connected to a voltage source, a cathode electrode of the cold cathode vacuum diode is connected in series with an anode electrode of the X-ray detection component, and a cathode electrode of the X-ray detection component is connected to the ammeter.
4. The high sensitivity X-ray detector of claim 1, wherein the photoconductor is a wide bandgap photoconductor or an avalanche photoconductor.
5. The high-sensitivity X-ray detector according to claim 4, wherein the photoconductor is fabricated with a P-N junction structure.
6. The high sensitivity X-ray detector of claim 5, wherein the P-N junction structure comprises P-Si/N-Ga2O3、p-Se/n-CdO、p-CdTe/n-CdS、p-PbO/n-PbO。
7. The high-sensitivity X-ray detector according to claim 5, wherein in the P-N junction structure, the first anode electrode is prepared on the N-type semiconductor side, and the first cathode electrode is prepared on the P-type semiconductor side.
8. The high-sensitivity X-ray detector of any one of claims 1-7, wherein the nanowire cold cathode emitter is a zinc oxide nanowire, a copper oxide nanowire, a tungsten oxide nanowire, a molybdenum oxide nanowire, an iron oxide nanowire, a titanium oxide nanowire, or a tin oxide nanowire.
9. The high-sensitivity X-ray detector according to claim 1, wherein the height of the spacer is 50 to 1000 μm.
10. The high-sensitivity X-ray detector of claim 1, wherein the vacuum gap has a vacuum degree of 10-7～10-3Pa。
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