JP2004006766A - X-ray detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an X-ray detector where the deterioration of the characteristics of an X-ray photoconductive film is reduced and an adhesion of a circuit board and the X-ray photoconductive film is improved. <P>SOLUTION: The X-ray detector comprises a plurality of pixel units which have the X-ray photoconductive films 16 converting the X-ray made incident from the outside into signal charges, pixel electrodes 14 to which the signal charges are inputted and switching elements controlling reading of the signal charges accumulated in charge accumulation elements through the pixel electrodes 14 and which are two-dimensionally arranged. The pixel electrodes 14 are made of alloy. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an X-ray detector that detects an X-ray image captured by X-rays.
[0002]
[Prior art]
In a medical diagnostic apparatus, for example, an X-ray is used for imaging a subject, and an X-ray detector is used for detecting an X-ray image of the subject. For example, intensifying screens or films have been used for still images for X-ray detectors, and image tubes have been used for moving images, for example.
[0003]
In recent years, a planar detector in which a plurality of X-ray detection elements are two-dimensionally arranged has attracted attention as a new generation X-ray detector. The planar detector is configured to output an X-ray image captured by X-rays or a real-time X-ray image as a digital signal. Further, since the planar detector is a solid state detector, improvement in image quality performance and stability are expected.
[0004]
Planar detectors for general radiography and chest radiography, which collect still images at a relatively large dose, have already been developed and commercialized.
[0005]
In the near future, even higher performance will enable the real-time detection of X-ray moving images of 30 or more screens per second under a see-through dose, and commercialization of products that are applied to fields such as cardiovascular and digestive organs. Is expected. In order to detect such an X-ray moving image, it is required to improve the S / N and to develop a real-time processing technique for a minute signal.
[0006]
Planar detectors are roughly classified into two types: a direct type and an indirect type.
[0007]
The direct method is a method of directly converting X-rays into signal charges using an X-ray photoconductive material such as a-Se, and storing the converted signal charges in a charge storage capacitor.
[0008]
In the direct method, a pixel unit 11, a charge storage unit 13, a TFT 15 and a Zener diode 17 are provided for each pixel two-dimensionally arranged on the detection surface, and a voltage input to the input side of the TFT 15 by the Zener diode 17 is applied to the TFT 15 There has already been proposed a detector for preventing the TFT (readout switch) 15 from being destroyed by outputting a charge to the charge accumulating section 13 when the voltage becomes a predetermined voltage lower than the voltage at which the TFT is destroyed (for example, Patent Document 1). 1).
[0009]
On the other hand, the indirect method converts X-rays into visible light using a scintillator material, converts the converted visible light into signal charges using an a-Si photodiode or CCD, and transfers the signal charges to a charge storage capacitor. This is an accumulation method.
[0010]
Note that in the indirect method, a plurality of switching elements 402 are provided in a matrix, a pixel electrode 503 is connected to each switching element, and a scanning line that sends a drive signal to each row of switching elements connected to each pixel electrode. A signal line connected to each row of switching elements is arranged, and an X-ray charge conversion film 403 made of a photosensitive material 110 containing inorganic semiconductor particles and a carrier transport material 109 containing an organic semiconductor is provided on each pixel electrode. A vessel has been proposed (for example, see Patent Document 2).
[0011]
Further, as an example related to Patent Document 2, an example in which the X-ray charge conversion film (109) is configured by a phosphor (110), a photoconductor (111), and a carrier transport material (112) has been proposed (for example, And Patent Document 3).
[0012]
Most of the planar detectors that have been announced so far are indirect systems. However, it is considered that the direct method has a higher possibility for higher performance.
[0013]
Incidentally, in the direct method, an X-ray photoconductive material is used to convert incident X-rays into signal charges. When applied to a medical X-ray detector, the X-ray photoconductive material is required to have a size enough to cover a human body, for example, a size of about 40 cm on a side. The X-ray photoconductive material is usually formed in a film having a uniform thickness on a circuit board provided with an electric circuit for storing and reading signal charges. Further, in order to sufficiently detect incident X-rays, a thickness of several hundred μm is required even when a material made of heavy metal and having a large specific gravity is used.
[0014]
An X-ray photoconductive material is a kind of semiconductor, and its properties may vary greatly depending on its crystal structure and composition. In general, the best properties are obtained in a single crystal state. However, a single crystal material having a sufficient size required for an X-ray detector has not been obtained.
[0015]
In the case of the direct method, the circuit board constituting the X-ray detector is manufactured by the same method as the manufacturing process of the liquid crystal display device. For example, a pixel electrode is formed on a surface of a circuit board, and an X-ray photoconductive film is provided on the surface of the circuit board. In order to selectively input the output of the X-ray photoconductive film to each pixel electrode, in many cases, for example, silicon oxide (SiO 2) is used to surround the pixel electrode.₂) Is provided.
[0016]
Aluminum or ITO is used for the pixel electrode.
[0017]
The X-ray photoconductive film is made of a material that efficiently converts X-rays into charge signals, for example, lead iodide (hereinafter PbI).₂Bismuth iodide (hereinafter referred to as BiI)₃Or HgI₂Is used.
[0018]
Therefore, aluminum or ITO used for the pixel electrode and PbI used for the X-ray photoconductive film are used.₂And BiI₃Or HgI₂Comes in direct contact.
[0019]
In the direct X-ray detector described above, the aforementioned PbI₂And BiI₃Or HgI₂Is formed in a film shape on the pixel electrode to a thickness of several hundred μm by, for example, a vacuum evaporation method. Further, an upper electrode for replenishing charges is further formed on the X-ray photoconductive film.
[0020]
[Patent Document 1]
JP-A-10-10237 (abstract, FIG. 1, paragraphs [0038] to [0048])
[0021]
[Patent Document 2]
JP 2001-264443 A (abstract, FIGS. 1 and 4, paragraphs [0033] to [0049])
[0022]
[Patent Document 3]
JP-A-2002-90460 (abstract, FIG. 1, paragraphs [0023] to [0048])
[0023]
[Problems to be solved by the invention]
In the above-described X-ray detector, an X-ray photoconductive film is formed on a circuit board on which an electric circuit portion for storing and reading signal charges is formed. In particular, since the circuit board uses a TFT obtained by diverting the manufacturing process of the liquid crystal display device, a component exposed on the surface of the circuit board, such as a pixel electrode or a substance used for an insulating layer provided around the pixel electrode, is used. The crystal lattice spacing and the X-ray photoconductive material used for the X-ray photoconductive film, ie, PbI₂And BiI₃Or HgI₂It greatly differs from the crystal lattice spacing such as. Therefore, when an X-ray photoconductive film is formed on a circuit substrate by a vacuum deposition method, the lattice spacing and symmetry of the crystal between the pixel electrode or the insulating layer and the X-ray photoconductive film are different, and the crystal of the X-ray photoconductive film is different. Growth is inhibited. As a result, the properties of the X-ray photoconductive film are deteriorated, or the adhesion at the interface between the two is reduced, and the X-ray photoconductive film is peeled off.
[0024]
The present invention solves the above-mentioned drawbacks, reduces the deterioration of the characteristics of the X-ray photoconductive film, and improves the adhesion between the circuit board and the X-ray photoconductive film. The purpose is to provide.
[0025]
[Means for Solving the Problems]
The present invention provides an X-ray photoconductive film that converts an X-ray incident from the outside into a signal charge, a pixel electrode to which the signal charge is input, and reading of the signal charge stored in a charge storage element via the pixel electrode. In the X-ray detector, each of which has a switching element for controlling the pixel electrode and a plurality of pixel units arranged two-dimensionally, the pixel electrode is formed of an alloy.
[0026]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described with reference to an exploded perspective view of FIG.
[0027]
The circuit board section 11 includes a holding substrate 12 made of glass or the like, an electric circuit layer 13 provided on the holding substrate 12, a plurality of pixel electrodes 14 located on the uppermost surface, and the like.
[0028]
The electric circuit layer 13 is provided with an electric circuit including a TFT structure similar to, for example, a pixel of a liquid crystal display device and accumulating and reading signal charges.
[0029]
The pixel electrode 14 is provided for each pixel corresponding to each of the TFT elements, and is two-dimensionally arranged in the vertical and horizontal directions.
[0030]
An X-ray photoconductive portion 15 for converting X-rays into signal charges is laminated on the surface (upper portion) of the circuit board portion 11. The X-ray photoconductive portion 15 includes, for example, an X-ray photoconductive film 16 located on the circuit board portion 11 side, an upper electrode 17 located on the X-ray photoconductive film 16, and the like.
[0031]
In the above configuration, the X-rays 18 incident on the X-ray photoconductive film 16 from the outside through the upper electrode 17 are converted into signal charges inside the X-ray photoconductive film 16.
[0032]
The signal charge generated in the X-ray photoconductive film 16 corresponds to the size of the incident X-ray 18, passes through the pixel electrode 14, and is formed on the electric circuit layer 13 through a charge storage element, for example, a capacitor (see FIG. 2). ) Is stored for each pixel. Thereafter, the signal charges are read out as electric signals for each pixel unit and reproduced as an X-ray image.
[0033]
Next, an electric circuit formed in the electric circuit layer 13 will be described with reference to an equivalent circuit in FIG. 2, parts corresponding to those in FIG. 1 are denoted by the same reference numerals, and duplicate description will be partially omitted.
[0034]
The circuit board unit 11 is provided with a plurality of pixel units 21.
[0035]
As shown in FIG. 2, the plurality of pixel units 21 including the pixel units 2111 to 21 nm are two-dimensionally arranged in a row direction (horizontal direction in the drawing) and a column direction (vertical direction in the drawing). Further, a pixel electrode 14 is provided for each pixel unit 21. The pixel electrode 14 is composed of the same number of pixel electrodes 1411 to 14 nm as the pixel unit 21.
[0036]
A control circuit 22 and a parallel / serial conversion circuit 23 are arranged on a part of the circuit board unit 11, for example, outside the pixel unit 21.
[0037]
Each pixel unit 21 includes, for example, a pixel electrode 14, a thin film transistor (TFT) 24 functioning as a switching element, a capacitor 25 for charge storage, and the like as shown in the pixel unit 21 nm.
[0038]
The TFT 24 has a gate electrode G, a source electrode S, and a drain electrode D. The source electrode S and the capacitor 25 of the TFT 24 are electrically connected to the pixel electrode 14.
[0039]
The control circuit 22 is provided with a plurality of control lines 26, that is, first to n-th control lines 261 to 26n. Each control line 26 is connected to the gate electrode G of the TFT 24 of each pixel unit located in the same row. For example, the first control line 261 is connected to the gate electrodes G of the individual TFTs 24 forming the pixel units 2111 to 211m of the first row.
[0040]
The parallel / serial conversion circuit 23 is connected to a plurality of read lines 27, that is, first to m-th m read lines 271 to 27m. Each readout line 27 is connected to the drain electrode D of the TFT 24 of each pixel unit 21 located in the same column. For example, the first read line 271 is connected to the drain electrode D of each TFT 24 defined by the pixel units 2111, 2121, 2131, and 21n1.
[0041]
In the above configuration, an ON signal is sequentially output from the control circuit 22 to the control lines 261 to 26m. For example, when an ON signal is output to the first control line 261, the TFT 24 connected to the first control line 261 is turned on. At this time, the signal charges stored in each pixel unit in which the TFT 24 is ON are read out and output to the drain electrode D as an electric signal. The electric signal output to the drain electrode D is input in parallel to the parallel / serial conversion circuit 23 via the read lines 271 to 27m. After that, the signal is converted into a serial signal by the parallel / serial conversion circuit 23 and sent to the next signal processing circuit.
[0042]
Thereafter, an OFF signal is applied to the first control line 261 to turn off the TFT 24 connected to the first control line 261. Next, an ON signal is output to the next second control line 262. Such an operation is sequentially performed for each row, the signal charges stored in all the pixel units are sequentially read as electric signals, and electric signals corresponding to one screen are output.
[0043]
Next, an example of a sectional structure of one pixel unit 21 will be described with reference to FIG.
[0044]
In FIG. 3, portions corresponding to FIGS. 1 and 2 are denoted by the same reference numerals, and a duplicate description will be partially omitted.
[0045]
As described above with reference to FIG. 1, the circuit board unit 11 covers the holding substrate 12 and the electric circuit layer 13 including the TFT structure formed on the holding substrate 12, and covers most of the surface of the circuit board unit 11. And a pixel electrode 14 provided.
[0046]
An X-ray photoconductive portion 15 is laminated on the upper portion of the circuit board portion 11 covering the pixel electrode 14. The X-ray photoconductive portion 15 includes an X-ray photoconductive film 16 located on the circuit board 11 side, an upper electrode 17 located on the uppermost surface, and the like.
[0047]
The X-ray photoconductive film 16 is made of a heavy metal material having semiconductor properties, for example, PbI₂And BiI₃Or HgI₂And the like are thin films formed to a uniform thickness of, for example, about 300 μm by a vacuum evaporation method.
[0048]
During operation, a voltage of about several hundred volts is applied between the pixel electrode 14 and the upper electrode 17, and an electric field is formed inside the X-ray photoconductive film 16.
[0049]
In the above-described configuration, when X-rays enter the X-ray photoconductive portion 15, the X-rays are absorbed in the X-ray photoconductive film 16, so that signal energy, for example, a pair of electrons and holes is generated by the energy. Many occur. The signal charges move due to the electric field inside the X-ray photoconductive film 16, and one of the electrons and the holes reaches the pixel electrode 14 and is stored in the capacitor 25 (see FIG. 2) provided in the electric circuit layer 13. .
[0050]
The signal charge stored in the capacitor (25) is read out by the operation described with reference to FIG. 2, for example, and is output as an electric signal.
[0051]
When an X-ray image is detected using the X-ray detector shown in FIGS. 1 to 3, the characteristics of the X-ray photoconductive portion 15, particularly, the properties of the X-ray photoconductive film 16 become important.
[0052]
A semiconductor material for forming the X-ray photoconductive film 16 such as PbI₂And BiI₃Or HgI₂Although good performance can be obtained in the state of a single crystal, the characteristics deteriorate when the crystal state is poor. Therefore, PbI₂And BiI₃Or HgI₂When the X-ray photoconductive film 16 is formed on the circuit board portion 11 using a material such as the above, it is necessary to form a film having good crystallinity from the vicinity of the surface of the circuit board portion 11.
[0053]
For example, if the crystal lattice of the pixel electrode 14 occupying most of the surface of the circuit board portion 11 and the crystal lattice of the X-ray photoconductive film 16 do not match, distortion occurs and the crystallinity of the X-ray photoconductive film 16 is broken. The characteristics deteriorate.
[0054]
However, PbI₂And BiI₃Or HgI₂Pure metals having similar crystallinity such that the lattice mismatch rate is several percent or less, preferably 1% or less, more preferably 0.5% or less with respect to X-ray photoconductive materials such as not exist. Although it is conceivable to use a substance other than a metal as the pixel electrode 14, it is difficult to secure the conductivity required for the pixel electrode.
[0055]
Also, an X-ray photoconductive material such as PbI₂Has a hexagonal crystal lattice. Among metals having the same hexagonal crystal lattice, the lattice spacing is PbI₂Nothing close to is found. However, in order to eliminate the lattice mismatch at the interface where two types of materials are in contact, it is necessary to match the symmetry of the crystal arrangement and the crystal lattice spacing on the surfaces of the respective materials constituting the interface. For example, the deviation of the crystal lattice spacing on the surface must be at least 0.5% or less, and in particular 0.1% or less to achieve good characteristics.
[0056]
Here, a method for eliminating lattice mismatch between the X-ray photoconductive material and the pixel electrode material will be described with reference to FIG. FIG. 4 schematically shows an example in which lead atoms P are arranged on the metal M surface without causing lattice mismatch.
[0057]
PbI₂Is [a = 4.56, c = 6.98].
[0058]
The lead atoms P have a hexagonal close-packed arrangement on a two-dimensional plane as shown by a solid line p, and the interval between the lead atoms P is about 45.6 μm. In addition, as shown by the dotted line m, the lead atoms P arranged in the hexagon p are stacked on the surface of the metal atoms M arranged in the hexagon while being rotated by 30 degrees with respect to the arrangement of the metal atoms M.
[0059]
In this case, when the lattice spacing of metal atoms M is, for example, 26.3 μm, the lattice spacing of lead atoms P is 45.6 μm, so that metal atoms M and lead atoms P are stacked with good crystal matching. This state is realized by calculation when the crystal lattice spacing of the lead atom P is √3 times the lattice spacing of the metal atom M. In general, if a substance having a metal atom M spacing of 26.3 μm, PbI₂Means that the layers are stacked with good crystal consistency at the interface with.
[0060]
Here, a metal atom having a hexagonal atomic arrangement and a crystal lattice spacing close to 26.3 μm is represented by Ni (24.9 μm), Cu (25.6 μm) if the distance between the atoms is shown in parentheses. , Rh (26.9 μm), Ir (27.1 μm), Pd (27.5 μm), Pt (27.7 μm), Al (28.6 μm) or Ag (28.9 μm).
[0061]
Each of these metals has a face-centered cubic crystal. When the crystal direction (111) is taken in a direction perpendicular to the metal surface, a hexagonal atomic arrangement is generated on the surface. Also, Co (25.1 μm) and Cr (27.2 μm) have a hexagonal crystal lattice. If the crystal direction (0001) is perpendicular to the metal surface, a hexagonal atomic arrangement is generated on the surface. I do.
[0062]
However, each of the above metal atoms is PbI₂2% or more of the crystal lattice spacing between them, and good lattice matching cannot be expected.
[0063]
Therefore, in the present invention, for example, a metal whose interatomic distance is shorter than 26.3 μm and a metal whose interatomic distance is longer than 26.3 μm are alloyed to make the average interatomic distance close to 26.3 μm.
[0064]
It is difficult to simply make the intermetallic distance close to 26.3 μm for a material forming an intermetallic compound between constituent metals in the process of alloying. Therefore, considering combinations of metals in which the formation of intermetallic compounds is small and the average interatomic distance is 26.3 μm, Ni-Rh, Ni-Ir, Ni-Pd, Ni-Ag, Cu-Ir or There are Co-Cr alloys.
[0065]
These alloys have an atomic number per unit volume of 7.77 × 10^-22Pieces / cm³Then, the interatomic distance becomes 26.3 μm.
[0066]
For example, in the case of a Ni-Pd alloy, a desired average interatomic distance can be obtained by making each alloy ratio approximately half. The average number of atoms of these alloys can be easily measured by X-ray diffraction analysis. For example, when the diffraction intensity is observed on the substrate surface obtained by X-ray diffraction at a vertical plane spacing of 21.5 μm, a desired interatomic distance is obtained.
[0067]
The above explanation describes that PbI₂Is used, but BiI₃The same applies to the case of using.
[0068]
BiI₃Is hexagonal and the lattice spacing is (a = 75.1 μm, c = 207.1 μm). That is, BiI₃For example, alloys that can obtain good lattice matching include Ni-Cu, Ni-Rh, Ni-Ir, and Ni-Pd alloys. These alloys have, for example, an atomic number per unit volume of 9.01 ×^-22Pieces / cm³, The average interatomic distance becomes 25.0 μm.
[0069]
This value (25.0 μm) is₃Is just １ ／ of the crystal lattice spacing of (75.1 μm). Also in this case, since both have an atomic arrangement based on a hexagon, good lattice matching, for example, a state in which metal atoms are stacked on each other is realized.
[0070]
The average number of atoms in these alloys is PbI₂As in the case of the above, it can be easily measured by X-ray diffraction analysis. For example, when diffraction intensity is observed on the substrate surface obtained by X-ray diffraction at a vertical plane spacing of 20.4 μm, a desired interatomic distance is obtained.
[0071]
Therefore, the pixel electrode located on the surface of the circuit board portion is formed of a material containing the above alloys as main components, and the X-ray photoconductor film is formed of PbI.₂And BiI₃In this case, an X-ray photoconductive film having good crystallinity with the pixel electrode can be obtained.
[0072]
Next, another embodiment of the present invention will be described with reference to FIG. In FIG. 5, portions corresponding to those in FIG. 3 are denoted by the same reference numerals, and duplicate description will be partially omitted.
[0073]
The X-ray detector shown in FIG. 5 includes a substance having a semiconductor property, for example, a material having a high resistance and an insulating property between the entire surface of the circuit board section 11, for example, between the circuit board section 11 and the X-ray photoconductive section 15. A semi-insulating layer 51 made of a low material is formed. In the semi-insulating layer 51, the X-ray photoconductive film 16 is made of PbI.₂In the case of chromium oxide (CrO₂) Or silicon nitride (SiNx).
[0074]
Chromium oxide is hexagonal and has a lattice spacing of 49.5 μmA, and PbI₂Has a lattice spacing close to the crystal spacing of (45.6 μm). Silicon nitride is also hexagonal and has a lattice spacing of 77.5 μm.₂Has a lattice spacing close to √3 times the crystal lattice spacing of
[0075]
Therefore, the crystal spacing between the X-ray photoconductive film 16 and the material of the semi-insulating layer 51 is close to each other, or the atoms of both are stacked, and the X-ray photoconductive film 16 having good crystallinity with the semi-insulating layer 51 is obtained. .
[0076]
For example, an insulating layer provided around a pixel electrode is required to have good insulating properties. However, insulating materials having sufficient insulating performance and having lattice matching with the X-ray photoconductor material are limited, which causes inconvenience in a circuit board manufacturing process. Further, even when the material of the pixel electrode has good crystal matching with the X-ray photoconductive film, the pixel electrode material may not be used due to the relationship between the X-ray photoconductive film and the insulating material.
[0077]
On the other hand, the provision of the semi-insulating layer 51 between the circuit board unit 11 and the X-ray photoconductive unit 15 eliminates the need for crystal matching between the pixel electrode or the insulating layer and the X-ray photoconductive film. The degree of freedom in selecting materials for electrodes and insulating layers is increased. In addition, there is an advantage that an X-ray photoconductive film having good crystallinity can be formed without changing the material used for the circuit board portion.
[0078]
In the above embodiment, since the semi-insulating layer 51 is made of a semi-insulating material such as chromium oxide or silicon nitride, it is different from a perfect insulator such as aluminum oxide or the like. And electrical continuity between the signal charges and the signal charges generated in the X-ray photoconductive film can be detected without any trouble. Further, since the conductivity is not high, insulation between the pixel electrodes is also ensured, and a decrease in resolution of the X-ray image is prevented.
[0079]
For example, chromium oxide and silicon nitride have high insulation properties, but have a band gap of about 5 eV, which is much lower than 9 eV of aluminum oxide, and are suitable as a material for the semi-insulating layer. In addition, these materials can change the resistivity by adjusting the amount of oxygen or the like at the time of forming the film. Therefore, the resistivity of the semi-insulating layer can be appropriately adjusted according to the required characteristics.
[0080]
Note that BiI is used as an X-ray photoconductive material.₃In the case where is used, indium nitride or silicon nitride can be used for the semi-insulating layer 51. Even when these materials are used, chromium oxide or silicon nitride and PbI₂The same effect as in the case of the combination is obtained.
[0081]
The lattice spacing of silicon nitride is 77.5 μm, and BiI₃Is a value close to the crystal lattice spacing of 75.1 μm. The lattice constant of indium nitride is 35.4 μm, which is 70.8 μm when a value of twice its period is obtained.₃Is close to the value of the crystal lattice spacing. Therefore, an X-ray photoconductive film having good crystallinity is formed on the semi-insulating layer 51.
[0082]
The semi-insulating layer 51 has HgI₂Can also be used. HgI₂Has a tetragonal crystal structure, and the lattice spacing is [a = 43.56 μm, b = 43.56 μm, c = 122.6 μm]. In addition, HgI₂In the case where is vacuum-deposited in the form of a thin film, the crystal state is stabilized by setting the direction of the C axis perpendicular to the substrate. In this case, a square crystal lattice including the a-axis and the b-axis appears at the interface with the semi-insulating layer 51, and the length of one side of the crystal lattice is 43.56 μm.
[0083]
As a material that can be used for the X-ray photoconductive film 16 and has a crystal lattice spacing close to 43.56 μm for obtaining consistency with the crystal lattice at the interface with the semi-insulating layer 51, cobalt monoxide, iron monoxide, Manganese oxide, cupric oxide, cubic silicon carbide, and the like are given.
[0084]
Regarding the above-mentioned materials, the crystal system, the lattice constant and the band gap are indicated.
Substance Crystal system Lattice constant Band gap
Cobalt monoxide {cubic} 42.67 μm 2.6 eV
Iron monoxide {cubic} 43.23 μm 2.4 eV
Manganese monoxide {cubic} 44.45 μm 3.8 eV
Dicopper monoxide {cubic} 42.70 μm 2.3 eV
Cubic silicon carbide {cubic} 43.57 μm @ 2.4 eV
It is.
[0085]
Note that the material raised above has a feature that a film with good crystallinity can be obtained because the material has a simple cubic crystal structure. Also, the value of the crystal lattice is HgI₂The crystal spacing between the a-axis and the b-axis is close to 43.56 μm, and the difference is at most 2%. Therefore, when these materials are used for the semi-insulating film 51, the X-ray photoconductive film to be further laminated is In addition, sufficient adhesion can be obtained without inhibiting the crystal growth of No. 16. In addition, since the above-described material is an insulator having a band gap of about 2 eV to 4 eV, a leakage current due to thermal fluctuation or the like is small, and a light resistance state can be maintained.
[0086]
By controlling the composition of any of the above-listed materials, the resistivity can be easily controlled, and both the conductivity and the insulation required for the semi-insulating layer 51 can be achieved. In addition, since they are oxides or carbides, the adhesion strength of the TFT substrate surface to a metal substance, an insulating substance, or the like can be improved.
[0087]
Cobalt monoxide and manganese monoxide both have a rock salt type crystal structure, and their lattice constants are HgI₂The former is 102% and the latter is 98%. Therefore, by using a mixture of cobalt monoxide and manganese monoxide in a ratio of about 1: 1 as the semi-insulating layer 51, the average lattice constant of the whole is HgI.₂, It is possible to further improve the characteristics and the adhesive force.
[0088]
Further, when a mixture of iron monoxide and manganese monoxide is used, the respective lattice constants are HgI₂Since the former is 102% and the latter is 98%, a good lattice constant can be obtained even if a mixture of cobalt monoxide and manganese monoxide is used for the semi-insulating layer.
[0089]
The present invention is not limited to the above embodiments, and various modifications and changes can be made at the stage of implementation without departing from the scope of the invention. In addition, the embodiments may be implemented in appropriate combinations as much as possible. In that case, the effects of the combinations are obtained.
[0090]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the deterioration of the characteristic of an X-ray photoconductive film is reduced, and the X-ray detector which improved the adhesiveness of a circuit board and an X-ray photoconductive film can be implement | achieved.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view for explaining an embodiment of the present invention.
FIG. 2 is a circuit configuration diagram for explaining an electric circuit formed in an electric circuit layer of the present invention.
FIG. 3 is a schematic cross-sectional view for explaining a pixel unit according to the present invention.
FIG. 4 is an explanatory diagram for explaining lattice matching of crystals between a material forming a pixel electrode and a material forming an X-ray photoconductive film according to the present invention.
FIG. 5 is a schematic cross-sectional view for explaining another embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 ... Circuit board part, 12 ... Holding board, 13 ... Electric circuit layer, 14 ... Pixel electrode, 15 ... X-ray photoconductive part, 16 ... X-ray photoconductive film, 17 ... Upper electrode, 18 ... X-ray, 21 ... Pixel unit, 22: control circuit, 23: parallel / serial conversion circuit, P: lead atom, M: metal atom.

Claims (9)

An X-ray photoconductive film for converting X-rays incident from the outside into signal charges, a pixel electrode to which the signal charges are input, and switching for controlling reading of the signal charges stored in the charge storage element via the pixel electrodes What is claimed is: 1. An X-ray detector, comprising: a plurality of pixel units, each of which has an element, wherein the pixel electrode is formed of an alloy. The X-ray photoconductive film mainly contains lead iodide, and the alloy is an alloy of nickel and rhodium and an alloy of nickel and iridium, an alloy of nickel and palladium, an alloy of nickel and silver, an alloy of copper and iridium, and an alloy of cobalt and chromium. 2. The X-ray detector according to claim 1, wherein any one of the alloys described above is used as a main component. The X-ray photoconductive film is mainly composed of bismuth iodide, and the alloy is mainly composed of one of an alloy of nickel and copper, an alloy of nickel and rhodium, an alloy of nickel and iridium, and an alloy of nickel and palladium. The X-ray detector according to claim 1. An X-ray photoconductive film for converting X-rays incident from the outside into signal charges, a pixel electrode to which the signal charges are input, and switching for controlling reading of the signal charges stored in the charge storage element via the pixel electrodes An X-ray detector including a circuit board portion provided with a plurality of pixel units having elements, wherein a semi-insulating film is provided between the X-ray photoconductive film and the circuit board portion. X-ray detector. 5. The X-ray detector according to claim 4, wherein the X-ray photoconductive film contains lead iodide as a main component, and the semi-insulating film contains chromium oxide or silicon nitride as a main component. 5. The X-ray detector according to claim 4, wherein the X-ray photoconductive film contains bismuth iodide as a main component, and the semi-insulating film contains indium nitride or silicon nitride as a main component. 5. The X-ray photoconductive film comprising mercury iodide as a main component, and the semi-insulating film containing any one of cobalt monoxide, iron monoxide, manganese monoxide, cupric oxide and cubic silicon carbide as a main component. The X-ray detector according to any one of the preceding claims. The X-ray detector according to claim 7, wherein the X-ray photoconductive film contains mercury iodide as a main component, and the semi-insulating film is a mixture of cobalt monoxide and manganese monoxide. The X-ray detector according to claim 7, wherein the X-ray light guide film contains mercury iodide as a main component, and the semi-insulating film is a mixture of iron monoxide and manganese monoxide.

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