Single nanowire X-ray detector and preparation method and application thereof

Abstract

The invention provides a single nanowire X-ray detector and a preparation method and application thereof. The single nanowire X-ray detector sequentially comprises a substrate, a single semiconductor nanowire, a composite metal source electrode and a composite metal drain electrode from bottom to top, wherein the composite metal source electrode and the composite metal drain electrode are attached to the surfaces of the two ends of the single semiconductor nanowire respectively. The single semiconductor nanowire comprises any one or a combination of at least two of a beta-Ga2O3 nanowire, a GaN nanowire, a SiC nanowire, a SnO2 nanowire, a GaAlN nanowire, an In2O3 nanowire or a NiO nanowire. The nanowire X-ray detector provided by the invention is high in responsivity, low in dark current, high in irradiation current, high in spatial resolution, short in response time and excellent in performance; moreover, compared with an existing X-ray detector made of a blocky material, the nanowire X-ray detector has obvious advantages of reducing the size of a device and realizing integration of the X-ray detector.

Description

Technical Field

[0001] The present invention belongs to the fields of semiconductor nanomaterials and semiconductor photodetectors, and relates to a single nanowire X-ray detector, a preparation method thereof, and an application thereof. Background Art

[0002] At present, X-ray detection means have been widely used in different fields such as scientific research, precision instrument detection, security inspection, and medical diagnosis and treatment. High sensitivity, high spatial resolution, fast response, and high on / off ratio have always been arduous challenges in the preparation of excellent X-ray detectors. With the in-depth exploration of researchers, the X-ray detection principle is mainly divided into two categories, including indirect and direct detection. Indirect detection is to convert X-rays into visible light through a scintillator and then use inductive coupling to collect and convert it into an electrical signal. Due to the afterglow effect and the Abbe diffraction limit of visible light in indirect X-ray detectors, the spatial resolution is low and the response time is slow. Direct detection is to directly convert X-rays into electrical signals using a semiconductor for collection. Because of the advantages of simple integrated system and relatively fast response time in direct X-ray detectors, they are considered the most ideal X-ray detectors. At present, commercial direct X-ray detectors are still limited by materials.

[0003] Currently, the photosensitive layer of common direct X-ray detectors is mainly bulk amorphous selenium material. The bulk amorphous selenium material has certain advantages in the early development of X-ray detectors due to its simple preparation process and low preparation cost. However, with the continuous development of modern X-ray technology, the disadvantages of bulk materials have gradually emerged. Nowadays, the requirements for spatial and temporal resolution in X-ray detection technology are constantly increasing. Due to the persistent photoconductivity (PCC) effect of some bulk semiconductors with a thickness of up to several hundred micrometers, the response time of X-ray detectors is too long, even reaching several seconds, which in turn affects the time resolution of X-ray detectors. At the same time, the spatial resolution of bulk materials often reaches more than several hundred micrometers, which is seriously unbalanced with the focusing size of several hundred nanometers of current X-ray sources.

[0004] Therefore, how to further improve the spatial and temporal resolution of X-ray detectors by reducing their size is a technical problem that urgently needs to be solved. Summary of the Invention

[0005] Aiming at the deficiencies of the existing technologies, the purpose of the present invention is to provide a single-nanowire X-ray detector, a preparation method thereof and an application. The single-nanowire X-ray detector provided by the present invention can ensure a sufficient length for X-ray absorption even when the diameter of the one-dimensional nanowire material is small enough, thereby ensuring that it has a sufficiently high spatial and temporal resolution and can generate an irradiation current that is easily collected. The single-nanowire X-ray detector and the nanowire X-ray detector array provided by the present invention have high responsivity, low dark current, high irradiation current, high spatial resolution and short response time, showing very superior performance; moreover, compared with the existing X-ray detectors made of bulk materials, the nanowire X-ray detector has obvious advantages in reducing the size of the device and realizing the integration of X-ray detectors.

[0006] To achieve the purpose of this invention, the following technical solutions are adopted:

[0007] In the first aspect, the present invention provides a single-nanowire X-ray detector, which sequentially includes a substrate, a single semiconductor nanowire, and a composite metal source electrode and a composite metal drain electrode respectively attached to the surfaces of both ends of the single semiconductor nanowire from bottom to top;

[0008] The single semiconductor nanowire includes any one or a combination of at least two of β-Ga2O3 nanowires, GaN nanowires, SiC nanowires, SnO2 nanowires, GaAlN nanowires, In2O3 nanowires or NiO nanowires.

[0009] In the present invention, due to its nanoscale size, the semiconductor nanowire has a high surface-to-volume ratio, and even when the diameter of the one-dimensional nanowire material is small enough, it can ensure a sufficient length for X-ray absorption and can generate an irradiation current that is easily collected; at the same time, the above materials all have a certain absorption ability in the X-ray band, can convert the absorbed X-ray energy into electron-hole pairs, realize direct photoelectric conversion, and thus generate a detectable electrical signal; in addition, the nanowire structure shortens the carrier transport distance due to its small diameter, which is beneficial to improving the response speed of the detector, enabling it to quickly and accurately detect the change of X-rays. The specific material type and the nanowire structure cooperate with each other, thereby ensuring that it has a sufficiently high X-ray absorption efficiency and spatial and temporal resolution.

[0010] Preferably, the bandgap of the single semiconductor nanowire > 3 eV, preferably > 4 eV, such as 3.2 eV, 3.4 eV, 3.6 eV, 3.8 eV, 4.0 eV, 4.5 eV or 5 eV, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0011] In the present invention, a wider bandgap can further reduce the dark current of the detector and improve the stability of the detector. When the energy of an X-ray photon is absorbed, the number of electron-hole pairs generated is proportional to the X-ray energy. Due to the large bandgap and low background noise, the detector can more accurately measure the number of these electron-hole pairs, thereby more accurately distinguishing X-rays of different energies and improving the energy resolution.

[0012] Preferably, the single semiconductor nanowire includes any one or a combination of at least two of β-Ga2O3 nanowires, SiC nanowires, In2O3 nanowires, or NiO nanowires, and is further preferably a β-Ga2O3 nanowire or a combination of β-Ga2O3 nanowires and In2O3 nanowires.

[0013] In the present invention, on the one hand, β-Ga2O3 nanowires have a relatively large bandgap, which results in lower thermal noise and dark current at room temperature, thereby improving the detection sensitivity and signal-to-noise ratio; on the other hand, β-Ga2O3 has a relatively high atomic number and stronger X-ray absorption ability, which can effectively convert X-ray photons into electron-hole pairs and improve the detection efficiency; in addition, β-Ga2O3 nanowires also have a relatively high electron mobility, which is conducive to the rapid transport of photo-generated carriers and reduces the recombination of carriers, thus improving the response speed of the detector. The interaction of the above aspects enables β-Ga2O3 to exhibit more excellent X-ray detection efficiency when used as an X-ray absorption material.

[0014] Preferably, the diameter of the single semiconductor nanowire is 1 nm to 1000 nm, preferably 50 nm to 200 nm, such as 1 nm, 20 nm, 50 nm, 100 nm, 150 nm, 200 nm, 400 nm, 600 nm, 800 nm, or 1000 nm, etc., but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0015] Preferably, the length of the single semiconductor nanowire is 1 μm to 1000 μm, further preferably 10 μm to 100 μm, such as 1 μm, 10 μm, 20 μm, 50 μm, 70 μm, 100 μm, 300 μm, 500 μm, 800 μm, or 1000 μm, etc., but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0016] Preferably, the distance between the composite metal source electrode and the composite metal drain electrode is 1 μm to 1000 μm, more preferably 10 μm to 100 μm, such as 1 μm, 10 μm, 20 μm, 50 μm, 70 μm, 100 μm, 300 μm, 500 μm, 800 μm or 1000 μm, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0017] In the present invention, the length of a single semiconductor nanowire and the distance between the composite metal source electrode and the composite metal drain electrode will affect the performance of the material. By controlling the length of a single semiconductor nanowire to be 1 μm to 1000 μm, further controlled to be 10 μm to 100 μm, and controlling the distance between the composite metal source electrode and the composite metal drain electrode to be 1 μm to 1000 μm, further controlled to be 10 μm to 100 μm, it is possible to effectively avoid the phenomenon of the decrease in the spatial resolution of the detector caused by the bending of the nanowire, which is beneficial to accurately positioning the response position of X-rays in the nanowire, thereby making the resolution of the imaging higher; moreover, sufficient length can ensure the absorption efficiency of X-rays, and appropriate distance can also effectively promote the collection of carriers by the source and drain electrodes, reduce the recombination probability of carriers during the transmission process, thereby improving the collection efficiency of carriers and enhancing the detection signal.

[0018] Preferably, the composite metal source electrode and the composite metal drain electrode each independently include a metal adhesion thin layer and a metal conductive layer from bottom to top, and the metal adhesion thin layer is disposed on the side close to the single semiconductor nanowire.

[0019] Preferably, the material of the metal adhesion thin layer includes any one of Ni, Cr, Ti or Al.

[0020] Preferably, the material of the metal conductive layer includes any one of Cu, Ag or Au.

[0021] Preferably, the material of the metal adhesion thin layer is Ti, and the material of the metal conductive layer is Au.

[0022] Preferably, the thickness of the metal adhesion thin layer is 1 nm to 10 nm, more preferably 6 nm to 10 nm, such as 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm or 10 nm, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0023] In the present invention, by controlling the thickness of the metal adhesion thin layer within the range of 1 nm to 10 nm, and further within the range of 6 nm to 10 nm, a closer and more uniform contact interface can be formed between the electrode and the semiconductor, which is beneficial to further reducing the contact resistance at the interface and making the transmission of carriers between the electrode and the semiconductor smoother.

[0024] Preferably, the thickness of the metal conductive layer is 40 nm to 100 nm, such as 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm or 100 nm, etc., but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0025] In the present invention, by controlling the thickness of the metal conductive layer within the range of 30 nm to 100 nm, and further within the range of 40 nm to 80 nm, it is more beneficial to balance the stability of subsequent welding and the material cost.

[0026] Preferably, the substrate includes a rigid substrate, and the rigid substrate includes any one of a silicon dioxide substrate, a sapphire substrate or a diamond substrate.

[0027] Preferably, a metal mark is provided on the substrate, and the metal mark is used to locate the single semiconductor nanowire.

[0028] Preferably, the metal mark includes a Cr / Au composite layer, and in the Cr / Au composite layer, the Cr layer is disposed on the side close to the substrate, and the Au layer is disposed on the side away from the substrate.

[0029] Preferably, the thickness of the Cr layer in the Cr / Au composite layer is 5 nm to 10 nm, and the thickness of the Au layer is 30 nm to 50 nm. For example, the thickness of the Cr layer is 5 nm, 6 nm, 7 nm, 8 nm, 9 nm or 10 nm, etc., and the thickness of the Au layer is 30 nm, 35 nm, 40 nm, 45 nm or 50 nm, etc., but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0030] In a second aspect, the present invention provides a method for preparing a single nanowire X-ray detector as described in the first aspect, and the preparation method includes:

[0031] S1. Prepare a semiconductor nanowire on the surface of a first substrate or directly prepare a semiconductor nanowire;

[0032] S2. On the first substrate on which the semiconductor nanowire is grown, prepare a composite metal source electrode and a composite metal drain electrode on the surfaces at both ends of the semiconductor nanowire respectively;

[0033] Alternatively, transfer the semiconductor nanowire onto a second substrate, and fabricate a composite metal source electrode and a composite metal drain electrode on the two end surfaces of the semiconductor nanowire respectively.

[0034] S3. Connect the composite metal source electrode and the composite metal drain electrode obtained in S2 to an external circuit respectively.

[0035] The single semiconductor nanowire includes any one or a combination of at least two of β-Ga2O3 nanowire, GaN nanowire, SiC nanowire, SnO2 nanowire, GaAlN nanowire, In2O3 nanowire or NiO nanowire.

[0036] Preferably, the method for fabricating the semiconductor nanowire in S1 includes any one of a solvothermal method, a template method, a chemical vapor deposition method or a physical vapor deposition method.

[0037] Preferably, the method for fabricating the composite metal source electrode and the composite metal drain electrode in S2 includes: first positioning a single semiconductor nanowire, then patterning an electrode structure on the two end surfaces of the single semiconductor nanowire, and finally fabricating the composite metal source electrode and the composite metal drain electrode in the region where the electrode structure is patterned.

[0038] In the present invention, by positioning the nanowire first, the accuracy of the positions of the composite metal source electrode and the drain electrode can be improved, and the fabrication efficiency can be enhanced.

[0039] Preferably, the method for patterning the electrode structure includes any one or a combination of at least two of a template method, an ultraviolet lithography method or an electron beam lithography method.

[0040] Preferably, when the method for patterning the electrode structure is an electron beam lithography method, the exposure dose is 1250 uC / cm 2 ~1450 uC / cm 2 , such as 1250 uC / cm 2 , 1270 uC / cm 2 , 1300 uC / cm 2 , 1350 uC / cm 2 , 1400 uC / cm 2 , 1420 uC / cm 2 or 1450 uC / cm 2 etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0041] In the present invention, by controlling the exposure dose within 1250 uC / cm 2 ~1450 uC / cm 2Within this range, it is more conducive to obtaining an electrode patterning region with an appropriate area, effectively avoiding the occurrence of photoresist residues or overexposure.

[0042] Preferably, the method for preparing the composite metal source electrode and the composite metal drain electrode in S2 independently includes any one of physical vapor deposition, electrochemical deposition, or chemical vapor deposition.

[0043] Preferably, the method for connecting the composite metal source electrode and the composite metal drain electrode to the external circuit in S3 includes pressure welding or silver paste bonding.

[0044] As a preferred technical solution of the present invention, the preparation method includes:

[0045] S1. Prepare semiconductor nanowires on the surface of the first substrate;

[0046] S2. Transfer the semiconductor nanowires to the second substrate, then use electron beam lithography to prepare electrode structure patterns on the surfaces at both ends of a single semiconductor nanowire, and finally prepare a composite metal source electrode and a composite metal drain electrode in the electrode structure pattern region, with an exposure dose of 1250 uC / cm 2 ~1450 uC / cm 2 ;

[0047] S3. Connect the composite metal source electrode and the composite metal drain electrode in S2 to the external circuit respectively;

[0048] The semiconductor nanowires in S1 include any one or at least two combinations of β-Ga2O3 nanowires, GaN nanowires, SiC nanowires, SnO2 nanowires, GaAlN nanowires, In2O3 nanowires, or NiO nanowires. The method for preparing the composite metal source electrode and the composite metal drain electrode in S2 independently includes any one of physical vapor deposition, electrochemical deposition, or chemical vapor deposition.

[0049] In the third aspect, the present invention also provides a nanowire X-ray detector array, which is composed of at least two single nanowire X-ray detectors described in the first aspect.

[0050] Preferably, the shape of the nanowire X-ray detector array includes a square.

[0051] In the present invention, by setting the X-ray detector array as a square, the square array has the same size and symmetry in the horizontal and vertical directions, which can make the imaging effect better.

[0052] Preferably, the distance between each adjacent single-nanowire X-ray detector is independently 0.5 μm to 100 μm, such as 0.5 μm, 1 μm, 2 μm, 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm or 100 μm, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0053] In the present invention, by independently controlling the distance between single-nanowire X-ray detectors within the range of 0.5 μm to 100 μm, signal crosstalk between adjacent detectors can be ensured not to occur, thereby improving the spatial resolution and being beneficial to the clarity of imaging.

[0054] The following are the preferred technical solutions of the present invention, but not limitations to the technical solutions provided by the present invention. Through the following preferred technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.

[0055] But not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0056] Compared with the prior art, the present invention has the following beneficial effects:

[0057] The single-semiconductor-nanowire detector and the semiconductor-nanowire detector array provided by the present invention have high responsivity, low dark current, high irradiation current, high spatial resolution, short response time, and exhibit very superior performance; moreover, compared with the existing X-ray detectors made of bulk materials, the nanowire X-ray detectors have obvious advantages in reducing the size of the device and realizing the integration of X-ray detectors. Brief Description of the Drawings

[0058] Figure 1 is a schematic structural diagram of a single-nanowire X-ray detector provided in Example 1.

[0059] Figure 2 is a schematic structural diagram of a nanowire X-ray detector array provided in Application Example 1.

[0060] Figure 3 is an SEM image of a single-nanowire X-ray detector provided in Example 1.

[0061] Figure 4 is an SEM image of β-Ga2O3 nanowires prepared in Example 1.

[0062] Figure 5 is an XRD pattern of β-Ga2O3 nanowires prepared in Example 1.

[0063] Figure 6Absorption spectrum of the β-Ga2O3 nanowires prepared in Example 1. The inset shows the optical bandgap of the extrapolated β-Ga2O3 nanowires.

[0064] Figure 7 Voltage-current curve of the single-nanowire X-ray detector provided in Example 1.

[0065] Figure 8 Transient response curve of the single-nanowire X-ray detector provided in Example 1.

[0066] In the figure: 1 - Substrate base layer; 2 - Substrate insulating layer; 3 - Single semiconductor nanowire; 4 - Metal adhesion thin layer; 5 - Metal conductive layer. Detailed implementation manners

[0067] The technical solutions of the present invention will be further described below through specific implementation manners. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0068] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above drawings are intended to cover non-exclusive inclusion.

[0069] Example 1

[0070] This example provides a single-nanowire X-ray detector, as Figure 1 shown, which includes a substrate base layer 1, a substrate insulating layer 2, a single semiconductor nanowire 3, and a composite metal source electrode and a composite metal drain electrode respectively attached to the two ends of the single semiconductor nanowire 3 from bottom to top. The composite metal source electrode and the composite metal drain electrode each independently include a metal adhesion thin layer 4 and a metal conductive layer 5 provided from bottom to top. The material of the substrate base layer 1 is Si, the material of the substrate insulating layer 2 is SiO2, the material of the single semiconductor nanowire 3 is β-Ga2O3, the material of the metal adhesion thin layer 4 is Ti, and the material of the metal conductive layer 5 is Au. Among them, the diameter of the nanowire is 100 nm, the length is 30 μm, the thickness of the Ti layer is 10 nm, the thickness of the Au layer is 100 nm, and the distance between the composite metal source electrode and the composite metal drain electrode is 10 μm. The preparation method is as follows:

[0071] (1) Prepare semiconductor nanowires on the surface of the first substrate

[0072] S1: Clean the c-Al2O3 substrate with acetone, isopropyl alcohol, and ultrapure water respectively, and then dry it with dry nitrogen gas; S2: Transfer the substrate in S1 to a thermal evaporation equipment, pump the vacuum degree in the growth chamber to 10 2 Pa by a mechanical pump, and then use a molecular pump to maintain the vacuum degree at 1×10 -3 Pa, control the evaporation rate at 0.02 nm / min, and evaporate 5-nm-thick metallic Au on the surface of the c-Al2O3 substrate; S3: Mix and grind Ga2O3 nano-powder and carbon nano-powder for 30 min, place the mixed powder above a quartz boat, place the substrate in S2 below the quartz boat, send the quartz boat into a two-stage chemical vapor deposition equipment, introduce argon gas into the chemical vapor deposition equipment to maintain for 30 min to remove air. Keep the argon gas flow rate at 400 sccm, and heat the chemical vapor deposition equipment at a heating rate of 5 °C / min to 1000 °C, maintain the temperature for 30 min and introduce oxygen at 3 sccm simultaneously to grow β-Ga2O3 nanowires.

[0073] (2) Prepare a composite metal source electrode and a composite metal drain electrode

[0074] S4: Transfer the substrate with grown nanowires in S3 into a 5-mL acetone solution, ultrasonically disperse it to obtain an acetone dispersion of β-Ga2O3 nanowires, transfer the acetone dispersion to a SiO2 / Si substrate with a metal label by a pipette gun, bake at 60 °C to volatilize the acetone, and leave the β-Ga2O3 nanowires on the SiO2 / Si substrate; S5: Spin-coat electron beam resist on the SiO2 / Si substrate described in S4, and set the rotation speed to 2500 rpm. Place the substrate spin-coated with electron beam resist on a hot stage for baking, set the baking temperature to 180 °C, and set the baking time to 2 min. Send the baked substrate into an electron beam exposure equipment, locate a single nanowire, and expose the electrode structure at both ends, and set the exposure dose to 1350 uC / cm 2 . After the exposed substrate is developed in a developer solution, transfer it to a fixing solution for fixing, set the developing time to 45 s, the developer solution is a volume ratio mixture of 4-methyl-2-pentanone: isopropyl alcohol = 1:3, and the fixing solution is isopropyl alcohol, and set the fixing time to 60 s. S6: Transfer the developed substrate into a thermal evaporation equipment, and maintain the vacuum degree in the growth chamber of the thermal evaporation equipment at 1×10 -3Set the deposition rate of metal Ti to 0.02 nm / min and deposit a 10-nm-thick metal Ti film. Switch to the Au source, set the deposition rate of metal Au to 0.02 nm / min and deposit a 100-nm-thick metal Au film. Transfer the substrate after evaporation coating into an acetone solution, maintain the temperature at 60 °C, and the heating time is 10 min. Dissolve the excess PMMA and remove the excess Au film in the acetone solution to obtain an X-ray detector for a single β-Ga2O3 nanowire.

[0075] (3) Connect the composite metal source electrode and the composite metal drain electrode to the external circuit respectively.

[0076] Example 2

[0077] This example provides an X-ray detector for a single nanowire, which includes a substrate base layer, a substrate insulating layer, a single semiconductor nanowire, and a composite metal source electrode and a composite metal drain electrode attached to the surfaces of both ends of the single semiconductor nanowire from bottom to top. The composite metal source electrode and the composite metal drain electrode each independently include a metal adhesion thin layer and a metal conductive layer arranged from bottom to top. The material of the substrate base layer is Si, the material of the substrate insulating layer is SiO2, the material of the single semiconductor nanowire is NiO, the material of the metal adhesion thin layer is Ti, and the material of the metal conductive layer is Au. Among them, the diameter of the nanowire is 50 nm, the length is 10 μm, the thickness of the Ti layer is 6 nm, the thickness of the Au layer is 40 nm, and the distance between the composite metal source electrode and the composite metal drain electrode is 8 μm. The preparation method is as follows:

[0078] (1) Prepare a semiconductor nanowire on the surface of the first substrate

[0079] S1: Clean the SiO2 / Si substrate with acetone, isopropyl alcohol, and ultrapure water respectively, and then blow it dry with dry nitrogen; S2, spin-coat electron beam resist PMMA on the SiO2 / Si substrate described in S1, and set the rotation speed to 3000 rpm. Place the substrate spin-coated with electron beam resist on a hot stage for baking, set the baking temperature to 180 °C, and the baking time to 2 min. Send the baked substrate into an electron beam exposure device to expose a nanowire array on the substrate. The length of the nanowire structure is 10 μm, the diameter is 50 nm, and the exposure dose is set to 1250 uC / cm 2After the exposed substrate is transferred into the developer for development and then into the fixer for fixing, the development time is set to 30 s, and the developer is a volume ratio mixture of 4-methyl-2-pentanone: isopropanol = 1:3. The fixer is isopropanol, and the fixing time is set to 40 s; S3: Transfer the developed substrate into a magnetron sputtering device, set the sputtering power to 200 W, the working pressure to 1.1 Pa, the oxygen-argon ratio to 1:10, and the growth sputtering time to 90 min. After sputtering is completed, take out the material; S4: Transfer the substrate with grown nanowires in S3 into an acetone solution, maintain the temperature at 60 °C, and the heating time is 10 min. Dissolve the excess PMMA and remove the unnecessary NiO thin layer in the acetone solution. Take out the substrate and blow it with nitrogen; S5: Transfer the substrate into a tube furnace and anneal it at 800 °C for 30 s in an air atmosphere to obtain a NiO nanowire array distributed on the substrate.

[0080] (2) Prepare a composite metal source electrode and a composite metal drain electrode

[0081] S6: On the SiO2 / Si substrate, spin-coat electron beam resist through a spin coater, and the rotation speed is set to 2500 rpm. Place the substrate spin-coated with electron beam resist on a hot stage for baking, the baking temperature is set to 180 °C, and the baking time is set to 2 min. Send the baked substrate into an electron beam exposure device, position a single nanowire, and expose the electrode structure at both ends. The exposure dose is set to 1250 uC / cm 2 After the exposed substrate is transferred into the developer for development and then into the fixer for fixing, the development time is set to 45 s, the developer is a volume ratio mixture of 4-methyl-2-pentanone: isopropanol = 1:3, the fixer is isopropanol, and the fixing time is set to 60 s; S6: Transfer the developed substrate into a thermal evaporation device, and maintain the vacuum degree of the growth chamber of the thermal evaporation device at 1 × 10 - 3 Pa, control the deposition rate of metal Ti to be 0.02 nm / min, and deposit a 6-nm-thick metal Ti film. Switch to an Au source, control the deposition rate of metal Au to be 0.02 nm / min, and deposit a 30-nm-thick metal Au film. Transfer the evaporated substrate into an acetone solution, maintain the temperature at 60 °C, and the heating time is 10 min. Dissolve the excess PMMA and remove the excess gold film in the acetone solution to obtain a single NiO nanowire X-ray detector.

[0082] (3) Connect the composite metal source electrode and the composite metal drain electrode to the external circuit respectively.

[0083] Example 3

[0084] This embodiment provides a single-nanowire X-ray detector, which includes a substrate base layer, a substrate insulating layer, a single semiconductor nanowire, and a composite metal source electrode and a composite metal drain electrode respectively attached to the surfaces of both ends of the single semiconductor nanowire from bottom to top. The composite metal source electrode and the composite metal drain electrode respectively and independently include a metal adhesion thin layer and a metal conductive layer arranged from bottom to top. The material of the substrate base layer is Si, the material of the substrate insulating layer is SiO2, the material of the single semiconductor nanowire is In2O3, the material of the metal adhesion thin layer is Cr, and the material of the metal conductive layer is Ag. Among them, the diameter of the nanowire is 200 nm, the length is 100 μm, the thickness of the Cr layer is 8 nm, the thickness of the Ag layer is 50 nm, and the distance between the composite metal source electrode and the composite metal drain electrode is 80 μm. The preparation method is as follows:

[0085] (1) Prepare a semiconductor nanowire on the surface of the first substrate

[0086] S1: Clean the c-Al2O3 substrate with acetone, isopropyl alcohol, and ultrapure water respectively, and then blow it dry with dry nitrogen; S2: Transfer the substrate in S1 to a thermal evaporation device, and pump the vacuum degree in the growth chamber to 10 2 Pa by a mechanical pump, and then maintain the vacuum degree at 1×10 -3 Pa by a molecular pump. Control the evaporation rate to be 0.02 nm / min, and evaporate a 5-nm-thick metal Au on the surface of the c-Al2O3 substrate; S3: Mix and grind the In2O3 nano-powder and the carbon nano-powder for 30 min. Place the mixed powder above the quartz boat, and place the substrate in S2 below the quartz boat. Send the quartz boat into a two-stage chemical vapor deposition device, and introduce argon into the chemical vapor deposition device to maintain for 30 min to remove air. Keep the argon flow rate at 400 sccm, and heat the chemical vapor deposition device at a heating rate of 5 °C / min to 950 °C, maintain the temperature for 30 min and introduce oxygen at 3 sccm at the same time to grow In2O3 nanowires.

[0087] (2) Prepare a composite metal source electrode and a composite metal drain electrode

[0088] S4: Transfer the substrate with grown nanowires in S3 into 5 mL of acetone solution, and ultrasonically disperse it to obtain an acetone dispersion of In2O3 nanowires. Transfer the acetone dispersion to a SiO2 / Si substrate with a metal label by a pipette gun, and bake it at 60 °C to volatilize the acetone, leaving the In2O3 nanowires on the SiO2 / Si substrate; S5: On the SiO2 / Si substrate described in S4, spin-coat electron beam resist by a spin coater with the rotation speed set at 2500 rpm. Place the substrate spin-coated with electron beam resist on a hot stage for baking, with the baking temperature set at 180 °C and the baking time set at 2 min. Send the baked substrate into an electron beam exposure device, locate a single nanowire, and expose electrode structures at both ends, with the exposure dose set at 1450 uC / cm 2 . After transferring the exposed substrate into a developer for development and then into a fixer for fixing, set the development time at 45 s, with the developer being a volume ratio mixture of 4-methyl-2-pentanone: isopropanol = 1:3, and the fixer being isopropanol, with the fixing time set at 60 s. S6: Transfer the developed substrate into a thermal evaporation device, maintain the vacuum degree of the growth chamber of the thermal evaporation device at 1×10 -3 Pa, control the deposition rate of metal Cr at 0.02 nm / min, and deposit a metal Cr film with a thickness of 8 nm. Switch to an Ag source, control the deposition rate of metal Ag at 0.02 nm / min, and deposit a metal Ag film with a thickness of 50 nm. Transfer the substrate after evaporation into an acetone solution, maintain the temperature at 60 °C, and heat for 10 min. Dissolve the excess PMMA and remove the excess gold film in the acetone solution to obtain an X-ray detector of a single In2O3 nanowire.

[0089] (3) Connect the composite metal source electrode and the composite metal drain electrode to an external circuit respectively.

[0090] Example 4

[0091] The difference between this example and Example 1 is that in this example, the material of the nanowire is SnO2. In step (1) S3, replace the Ga2O3 nano powder with SnO2 nano powder, and reduce the growth temperature to 800 °C;

[0092] The remaining preparation methods and parameters are the same as those in Example 1.

[0093] Example 5

[0094] The difference between this example and Example 1 is that in this example, the diameter of the nanowire is 400 nm; in step (1) S2, change the argon gas flow rate of chemical vapor deposition to 350 sccm.

[0095] The remaining preparation methods and parameters are the same as those in Example 1.

[0096] Example 6

[0097] The difference between this embodiment and Embodiment 1 is that in this embodiment, the length of the nanowire is 500 μm, and the temperature of chemical vapor deposition is changed to 1100 °C in step (1) S2.

[0098] The remaining preparation methods and parameters are the same as those in Embodiment 1.

[0099] Embodiment 7

[0100] The difference between this embodiment and Embodiment 1 is that in this embodiment, the source drain electrode is an Au electrode, and the deposition of the Ti layer is not performed in step (2) S6;

[0101] The remaining preparation methods and parameters are the same as those in Embodiment 1.

[0102] Comparative Example 1

[0103] The difference between this comparative example and Embodiment 1 is that in this comparative example, the material of the nanowire is ZnO nanowire. In step (1) S3, the Ga2O3 nanopowder is replaced with ZnO powder, and the growth temperature is reduced to 900 °C;

[0104] The remaining preparation methods and parameters are the same as those in Embodiment 1.

[0105] Application Example 1

[0106] This application example provides a nanowire X-ray detector array. As Figure 2 shown, taking 200 μm × 200 μm as the structure preparation area, it is composed of 5 × 4 single semiconductor nanowire detectors. The row spacing of each detector is 40 μm, and the column spacing is 40 μm. The structure and parameters of the single nanowire X-ray detector are the same as those of the single nanowire X-ray detector provided in Embodiment 1, including a substrate base layer 1, a substrate insulating layer 2, a single semiconductor nanowire 3 from bottom to top, and a composite metal source electrode and a composite metal drain electrode attached to the surfaces at both ends of the single semiconductor nanowire. The metal electrode includes a metal adhesion thin layer 4 and a metal conductive layer 5 from bottom to top;

[0107] In step (2) S5 of the preparation method, 20 nanowires are positioned simultaneously according to the shape of the detector array and the distance between each detector;

[0108] The remaining preparation methods and parameters are the same as those in Embodiment 1.

[0109] Application Example 2

[0110] This application example provides a nanowire X-ray detector array. With a 200μm×200μm as the structure preparation area, it consists of 10×10 single nanowire X-ray detectors. The row spacing of each detector is 10μm, and the column spacing is 20μm. The structure and parameters of the single nanowire X-ray detector are the same as those in Example 1;

[0111] In step (2) S5, 100 nanowires are positioned simultaneously according to the shape of the detector array and the distance between each detector;

[0112] All other preparation methods and parameters are the same as those in Example 1.

[0113] Application Example 3

[0114] This application example provides a nanowire X-ray detector array. With a 200μm as the structure preparation area, it consists of 2×2 single nanowire X-ray detectors. The row spacing of each detector is 90μm, and the column spacing is 100μm. The structure and parameters of the single semiconductor nanowire detector are the same as those in Example 1;

[0115] In step (2) S5, 4 nanowires are positioned simultaneously according to the shape of the detector array and the distance between each detector;

[0116] All other preparation methods and parameters are the same as those in Example 1.

[0117] Structure Test

[0118] The single nanowire X-ray detector prepared in Example 1 is subjected to SEM test, and the β-Ga2O3 nanowire prepared in Example 1 is subjected to SEM, XRD, and absorption spectrum tests. The test results are as Figures 3 - 6 shown.

[0119] Performance Test

[0120] Under the test conditions of a bias voltage of 5V and a dose rate of 23.7μGy / s, the single nanowire X-ray detectors prepared in Examples 1-7 and the nanowire X-ray detector arrays prepared in Application Examples 1-3 are subjected to X-ray photoelectric tests. The test results are as Figures 7 - 8 well as shown in Tables 1-2.

[0121] Table 1

[0122] Serial number Dark current (A) Photocurrent (A) Response time (s) Example 1 <![CDATA[5×10 -13 > <![CDATA[2×10 -9 > 0.08 Example 2 <![CDATA[4×10 -11 > <![CDATA[8×10 -9 > 0.06 Example 3 <![CDATA[1×10 -11 > <![CDATA[9×10 -10 > 0.1 Example 4 <![CDATA[1×10 -10 > <![CDATA[7×10 -10 > 0.1 Example 5 <![CDATA[4×10 -13 > <![CDATA[3×10 -9 > 0.23 Example 6 <![CDATA[1×10 -13 > <![CDATA[5×10 -10 > 0.25 Example 7 <![CDATA[6×10 -13 > <![CDATA[2×10 -10 > 0.8 Comparative Example 1 <![CDATA[1×10 -10 > <![CDATA[1×10 -9 > 1

[0123] Table 2

[0124] Serial number Number of detection elements Resolution of a single detector (μm) Aspect ratio of pixel points Application Example 1 20 40×40 0.8 Application Example 2 100 20×20 1 Application Example 3 4 100×100 1

[0125] From Figure 3It can be seen that through the preparation method provided by the present invention, a single semiconductor nanowire detector has been successfully fabricated, and the nanowire is straight; from Figure 4 it can be seen that the diameter of the nanowire is about 100 nm and the length is about 20 μm. The surface of the nanowire is smooth, and there is a circular gold particle catalyst at the top of the nanowire; from Figure 5 it can be known that the spectrum obviously conforms to jade-pdf-431012, which conforms to the basic characteristics of monoclinic β-Ga2O3; Figure 6 The figure is the energy band gap curve graph of the material converted by the Tauc Plot method. It can be seen that the energy band gap of the prepared β-Ga2O3 is 5.3 eV, and the energy band gap is relatively large.

[0126] From Figure 7 it can be seen that when the bias voltage is 10 V, the irradiation current of the single nanowire X-ray detector prepared in Example 1 can reach 2 nA, and the dark current is only 100 fA to 300 fA; from Figure 8 it can be known that the detector prepared in Example 1 shows good periodic repeatability, and the response time is less than 0.2 s, showing the characteristic of fast response.

[0127] From the data of Examples 1-3 and Comparative Example 1 in Table 1, it can be known that for the single nanowire X-ray detector provided by the present invention, the specific material type and the structure of the nanowire cooperate with each other, effectively reducing the dark current of the detector and improving the response speed of the detector; from the data comparison between Example 1 and Examples 4-7, it can be known that in the present invention, the type of nanowire material, the diameter and length of the nanowire, and the structure setting of the source and drain electrodes will all affect the performance of the detector. By using any one of β-Ga2O3 nanowires, In2O3 nanowires, and NiO nanowires as the nanowire material, controlling the diameter of the nanowire within the range of 50 nm to 200 nm and the length within the range of 10 μm to 100 μm, and using a composite metal electrode, the response speed of the detector can be further improved, and the detector shows more excellent performance.

[0128] From Table 2, it can be seen that within the same detector preparation area, the more the number of detection elements, the higher the resolution of the detector. However, when the number of detection elements reaches a certain density, the improvement effect on the resolution no longer increases, but the manufacturing cost increases significantly.

[0129] The applicant declares that the above description is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A single nanowire X-ray detector, characterized in that: The single nanowire X-ray detector includes, from bottom to top, a substrate, a single semiconductor nanowire, and a composite metal source electrode and a composite metal drain electrode respectively attached to the surfaces of both ends of the single semiconductor nanowire; The single semiconductor nanowire includes any one of β-Ga2O3 nanowire, GaN nanowire, SiC nanowire, SnO2 nanowire, GaAlN nanowire, In2O3 nanowire or NiO nanowire, or a combination of at least two thereof.

2. The single nanowire X-ray detector according to claim 1, characterized in that: The bandgap width of the single semiconductor nanowire is greater than 3 eV, preferably greater than 4 eV; Preferably, the single semiconductor nanowire comprises any one of β-Ga2O3 nanowire, SiC nanowire, In2O3 nanowire or NiO nanowire, or a combination of at least two thereof, and is further preferably β-Ga2O3 nanowire or a combination of β-Ga2O3 nanowire and In2O3 nanowire.

3. The single nanowire X-ray detector according to claim 1 or 2, characterized in that: The diameter of the single semiconductor nanowire is 1 nm to 1000 nm, preferably 50 nm to 200 nm; Preferably, the length of the single semiconductor nanowire is 1 μm to 1000 μm, more preferably 10 μm to 100 μm.

4. The single nanowire X-ray detector according to any one of claims 1 to 3, characterized in that: The distance between the composite metal source electrode and the composite metal drain electrode is 1 μm to 1000 μm, preferably 10 μm to 100 μm; Preferably, the composite metal source electrode and the composite metal drain electrode independently include a metal adhesion thin layer and a metal conductive layer from bottom to top, and the metal adhesion thin layer is arranged on a side close to the single semiconductor nanowire; Preferably, the material of the metal adhesion thin layer includes any one of Ni, Cr, Ti or Al; Preferably, the material of the metal conductive layer includes any one of Cu, Ag or Au; Preferably, the material of the metal adhesion thin layer is Ti, and the material of the metal conductive layer is Au; Preferably, the thickness of the metal adhesion thin layer is 1 nm to 10 nm, more preferably 6 nm to 10 nm; Preferably, the thickness of the metal conductive layer is 40 nm to 100 nm.

5. The single nanowire X-ray detector according to any one of claims 1 to 4, characterized in that: The substrate comprises a rigid substrate, and the rigid substrate comprises any one of a silicon dioxide substrate, a sapphire substrate or a diamond substrate; Preferably, a metal mark is provided on the substrate, and the metal mark is used to locate the single semiconductor nanowire; Preferably, the metal marker comprises a Cr / Au composite layer, wherein the Cr layer of the Cr / Au composite layer is arranged on a side close to the substrate, and the Au layer is arranged on a side away from the substrate; Preferably, in the Cr / Au composite layer, the thickness of the Cr layer is 5 nm to 10 nm, and the thickness of the Au layer is 30 nm to 50 nm.

6. A method for preparing a single nanowire X-ray detector according to any one of claims 1 to 5, characterized in that: The preparation method comprises: S1, preparing semiconductor nanowires on the surface of a first substrate or directly preparing semiconductor nanowires; S2, on the first substrate for growing the semiconductor nanowire, preparing a composite metal source electrode and a composite metal drain electrode on the surfaces of both ends of the semiconductor nanowire respectively; Or, transferring the semiconductor nanowire to a second substrate, and preparing a composite metal source electrode and a composite metal drain electrode on the surfaces of both ends of the semiconductor nanowire respectively; S3, connecting the composite metal source electrode and the composite metal drain electrode described in S2 to an external circuit respectively; The single semiconductor nanowire includes any one of β-Ga2O3 nanowire, GaN nanowire, SiC nanowire, SnO2 nanowire, GaAlN nanowire, In2O3 nanowire or NiO nanowire, or a combination of at least two thereof.

7. The method for preparing a nanowire X-ray detector according to claim 6, characterized in that: S1 The method for preparing semiconductor nanowires comprises any one of a solvent method, a template method, a chemical vapor deposition method or a physical vapor deposition method; Preferably, the method for preparing the composite metal source electrode and the composite metal drain electrode in S2 comprises: first positioning a single semiconductor nanowire, then patterning the electrode structure on the surfaces of both ends of the single semiconductor nanowire, and finally preparing the composite metal source electrode and the composite metal drain electrode in the region where the electrode structure is patterned; Preferably, the electrode structure patterning method includes any one of a template method, an ultraviolet lithography method or an electron beam exposure method, or a combination of at least two thereof; Preferably, when the electrode structure patterning method is electron beam exposure, the exposure dose is 1250uC / cm 2 ~1450uC / cm 2 ; Preferably, the method for preparing the composite metal source electrode and the composite metal drain electrode in S2 independently comprises any one of physical vapor deposition, electrochemical deposition or chemical vapor deposition; Preferably, the method of connecting the composite metal source electrode and the composite metal drain electrode to the external circuit respectively in S3 comprises pressure welding or silver paste bonding.

8. The method for preparing a single nanowire X-ray detector according to claim 6, characterized in that: The preparation method comprises: S1, preparing semiconductor nanowires on a first substrate surface; S2, transferring the semiconductor nanowire to a second substrate, and then using electron beam exposure to prepare electrode structure patterns on the surfaces of both ends of the single semiconductor nanowire, and finally preparing a composite metal source electrode and a composite metal drain electrode in the electrode structure pattern area, with an exposure dose of 1250uC / cm 2 ~1450uC / cm 2 ; S3, connecting the composite metal source electrode and the composite metal drain electrode described in S2 to an external circuit respectively; S1 The semiconductor nanowires include any one of β-Ga2O3 nanowires, GaN nanowires, SiC nanowires, SnO2 nanowires, GaAlN nanowires, In2O3 nanowires or NiO nanowires, or a combination of at least two thereof. S2 The methods for preparing the composite metal source electrode and the composite metal drain electrode each independently include any one of physical vapor deposition, electrochemical deposition or chemical vapor deposition.

9. A nanowire X-ray detector array, characterized in that: The nanowire X-ray detector array is composed of at least two single nanowire X-ray detectors as described in any one of claims 1-5.

10. The nanowire X-ray detector array according to claim 9, characterized in that: The shape of the nanowire X-ray detector array includes a square; Preferably, the row spacing and column spacing of each adjacent single nanowire X-ray detector are independently 0.5 μm to 100 μm.

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