Radiation detector with scintillator

Abstract

A radiation detector (300, 500) is disclosed herein, comprising a first pixel (150); a first reflector (314); and a first scintillator (316), wherein the first reflector (314) is configured to direct substantially all photons emitted by the first scintillator (316) into the first pixel (150). The first reflector (314) is configured to reflect photons emitted by the first scintillator (316) toward the first reflector (314). The first scintillator (316) is substantially completely surrounded by the first reflector (314) and the first pixel (150).

Description

[Technical field]

[0001] The disclosure herein relates to radiation detectors. [Background technology]

[0002] A radiation detector is a device that measures a property of radiation. Examples of the properties may include the spatial distribution of the intensity, phase, and polarization of the radiation. The radiation may be radiation that has interacted with an object. For example, the radiation measured by the radiation detector may be radiation that has penetrated or reflected from an object. The radiation may be electromagnetic radiation, such as infrared light, visible light, ultraviolet light, X-rays, or gamma rays. The radiation may be other types, such as alpha rays and beta rays. The radiation may include radiation particles, such as photons (electromagnetic waves) and subatomic particles. [Summary of the invention]

[0003] Disclosed herein is a radiation detector comprising a first pixel; a first reflector; and a first scintillator, wherein the first reflector is configured to direct substantially all photons emitted by the first scintillator into the first pixel.

[0004] According to an embodiment, the first reflector is in direct physical contact with the first scintillator.

[0005] According to an embodiment, the first scintillator is in direct physical contact with the first pixel.

[0006] According to an embodiment, the radiation detector further comprises a second pixel adjacent to the first pixel; a second reflector; and a second scintillator, wherein the second reflector is configured to direct substantially all photons emitted by the second scintillator into the second pixel.

[0007] According to an embodiment, the first reflector is in direct physical contact with the second reflector.

[0008] According to an embodiment, the radiation detector further includes a third pixel adjacent to the first pixel; a third reflector; and a third scintillator, wherein the third reflector is configured to guide substantially all photons emitted by the third scintillator into the third pixel.

[0009] According to an embodiment, the first reflector is configured to reflect photons emitted by the first scintillator towards the first reflector.

[0010] According to an embodiment, the first reflector is not opaque to radiation particles which, when incident on the first scintillator, enable the first scintillator to emit photons.

[0011] According to an embodiment, the first scintillator is substantially completely surrounded by the first reflector and the first pixel.

[0012] According to an embodiment, the radiation detector further comprises a fourth reflector; and a fourth scintillator, wherein the fourth reflector is configured to direct substantially all photons emitted by the fourth scintillator into the first pixel.

[0013] According to an embodiment, the first reflector comprises a material selected from the group consisting of aluminum, silver, gold, copper and any combination thereof.

[0014] According to an embodiment, the first scintillator comprises sodium iodide.

[0015] According to an embodiment, the first scintillator comprises quantum dots.

[0016] According to an embodiment, the radiation detector further comprises a first substrate, wherein the first scintillator is in a recess in a surface of the first substrate.

[0017] According to an embodiment, a portion of the first reflector is arranged on a side wall of the recess.

[0018] According to an embodiment, a portion of the first reflector is arranged on an end wall of the recess.

[0019] According to an embodiment, the recess has a frustoconical shape.

[0020] According to an embodiment, the first substrate comprises silicon or silicon dioxide.

[0021] According to an embodiment, the radiation detector further comprises a second substrate, wherein the first pixels are in the second substrate.

[0022] According to an embodiment, the radiation detector further comprises a sealing layer disposed between the first substrate and the second substrate, wherein the sealing layer is not opaque to photons emitted by the first scintillator.

[0023] A method of operating a radiation detector is disclosed herein, comprising exposing a first scintillator of the radiation detector to a first radiation particle, thereby causing emission of a first photon from the first scintillator; and using a first reflector of the radiation detector to direct substantially all of the photons emitted by the first scintillator into a first pixel of the radiation detector.

[0024] According to an embodiment, the first reflector is in direct physical contact with the first scintillator.

[0025] According to an embodiment, the first scintillator is in direct physical contact with the first pixel.

[0026] According to an embodiment, the method further comprises determining a characteristic of the first radiation particle based on the first photon.

[0027] According to an embodiment, the characteristic is the energy of the first radiation particle or the radiation flux of the first radiation particle.

[0028] According to an embodiment, the method further includes exposing a second scintillator of the radiation detector to second radiation particles, thereby causing emission of second photons from the second scintillator; and using a second reflector of the radiation detector to guide substantially all of the photons emitted by the second scintillator into a second pixel of the radiation detector, wherein the second pixel is adjacent to the first pixel.

[0029] According to an embodiment, the first reflector is in direct physical contact with the second reflector.

[0030] According to an embodiment, the method further includes exposing a third scintillator of the radiation detector to third radiation particles, thereby causing emission of third photons from the third scintillator; and using a third reflector of the radiation detector to guide substantially all of the photons emitted by the third scintillator into a third pixel of the radiation detector, wherein the third pixel is adjacent to the first pixel.

[0031] According to an embodiment, the directing comprises reflecting photons emitted by the first scintillator towards the first reflector using the first reflector.

[0032] According to an embodiment, the first reflector is not opaque to the first radiation particles.

[0033] According to an embodiment, the first scintillator is substantially completely surrounded by the first reflector and the first pixel.

[0034] According to an embodiment, the method further includes exposing a fourth scintillator of the radiation detector to fourth radiation particles, thereby causing emission of fourth photons from the fourth scintillator; and using a fourth reflector of the radiation detector to guide substantially all of the photons emitted by the fourth scintillator into a fourth pixel of the radiation detector.

[0035] According to an embodiment, the first reflector comprises a material selected from the group consisting of aluminum, silver, gold, copper and any combination thereof.

[0036] According to an embodiment, the first scintillator comprises quantum dots.

[0037] According to an embodiment, the radiation detector comprises a first substrate, and wherein the first scintillator is in a recess in a surface of the first substrate.

[0038] According to an embodiment, a portion of the first reflector is arranged on a side wall of the recess.

[0039] According to an embodiment, a portion of the first reflector is arranged on an end wall of the recess.

[0040] According to an embodiment, the recess has a frustoconical shape.

[0041] According to an embodiment, the first substrate comprises silicon or silicon dioxide.

[0042] According to an embodiment, the radiation detector further comprises a second substrate, and the first pixel is in the second substrate.

[0043] According to an embodiment, the radiation detector further comprises a sealing layer disposed between the first substrate and the second substrate, and wherein the sealing layer is not opaque to photons emitted by the first scintillator.

[0044] A method is disclosed herein, comprising forming a first recess on a surface of a first substrate; forming a first reflector on a wall of the first recess; forming a first scintillator in the first recess; and bonding a second substrate having pixels to the first substrate, wherein the first reflector is configured to guide substantially all photons emitted by the first scintillator into the pixels.

[0045] According to an embodiment, the first reflector is in direct physical contact with the first scintillator.

[0046] According to an embodiment, the first scintillator is in direct physical contact with the pixel.

[0047] According to an embodiment, the first reflector is configured to reflect photons emitted by the first scintillator towards the first reflector.

[0048] According to an embodiment, the first scintillator is substantially completely surrounded by the first reflector and the pixels.

[0049] According to an embodiment, the method further includes forming a second recess on the surface of the first substrate; forming a second reflector on the wall of the second recess; and forming a second scintillator in the second recess, wherein the second reflector is configured to guide substantially all photons emitted by the second scintillator into the pixel.

Brief Description of the Drawings

[0050] Figure 1 An image sensor according to an embodiment is schematically illustrated.

[0051] Figure 2AA simplified cross-sectional view of the image sensor according to an embodiment is schematically shown.

[0052] Figure 2B A detailed cross-sectional view of the image sensor according to an embodiment is schematically shown.

[0053] Figure 2C An alternative detailed cross-sectional view of the image sensor according to an embodiment is schematically shown.

[0054] Figure 3A Schematically illustrating the embodiment including Figure 2B of a radiation detector of the image sensor.

[0055] Figure 3B Schematically illustrating the Figure 3A A perspective view of a portion of the radiation detector.

[0056] Figure 3C Shown is how a reflector according to an embodiment directs photons emitted by an associated scintillator.

[0057] Figure 4A-4H Schematically illustrating the Figure 3A The radiation detector is formed.

[0058] Figure 5A , Figure 5B and Figure 5C The formation of an alternative radiation detector according to an embodiment is schematically illustrated. [Specific implementation method]

[0059] Figure 1 The image sensor 100 is schematically shown as an example. The image sensor 100 may have an array of pixels 150. The pixel array may be a rectangular array (eg Figure 1 ), a honeycomb array, a hexagonal array, or any other suitable array. Figure 1 In the example of FIG. 1 , the array of pixels 150 has 4 rows and 7 columns; however, in general, the array of pixels 150 may have any number of rows and any number of columns.

[0060] Each of the pixels 150 may be configured to detect radiation from a radiation source incident thereon, and may be configured to measure characteristics of the radiation (e.g., energy, wavelength, and frequency of the radiation particles). For example, each pixel 150 may be configured to count the number of radiation particles whose energy falls into a plurality of energy bins incident thereon over a period of time. All of the pixels 150 may be configured to count the number of radiation particles in a plurality of energy bins incident thereon over the same period of time. When the incident radiation particles have similar energies, the pixel 150 may be simply configured to count the number of radiation particles incident thereon over a period of time without measuring the energy of the individual radiation particles.

[0061] Each pixel 150 may have its own analog-to-digital converter (ADC) configured to digitize an analog signal representing the energy of an incident radiation particle into a digital signal, or to digitize an analog signal representing the total energy of multiple incident radiation particles into a digital signal. The pixels 150 may be configured to operate in parallel. For example, while one pixel 150 is measuring an incident radiation particle, another pixel 150 may be waiting for another radiation particle to arrive. The pixels 150 may not necessarily be individually addressable.

[0062] The image sensor 100 described herein may have applications such as X-ray telescopes, mammography, industrial X-ray defect detection, X-ray microscopy or X-ray microphotography, X-ray casting inspection, X-ray nondestructive testing, X-ray weld inspection, X-ray digital subtraction angiography, etc. The image sensor 100 is also suitable for replacing photographic plates, photographic films, PSP plates, X-ray image intensifiers, scintillators, or other semiconductor X-ray detectors. The image sensor 100 may also be used as an image sensor for detecting visible light photons that comprise an image of an object.

[0063] Figure 2A Schematically illustrating the Figure 1 2A-2A. More specifically, the image sensor 100 may include a radiation absorbing layer 110 and an electronic layer 120 (e.g., an ASIC) for processing or analyzing an electrical signal of incident radiation generated in the radiation absorbing layer 110. The image sensor 100 may or may not include a scintillator (not shown). The radiation absorbing layer 110 may include a semiconductor material such as silicon, germanium, GaAs, CdTe, CdZnTe, or a combination thereof. The semiconductor material may have a high mass attenuation coefficient for the radiation of interest.

[0064] Figure 2B Schematically showing as an example Figure 1Detailed cross-sectional view of the image sensor 100 along line 2A-2A in . More specifically, the radiation absorbing layer 110 may include one or more diodes (e.g., pin or pn) composed of one or more discrete regions 114 of a first doped region 111, a second doped region 113. The second doped region 113 may be separated from the first doped region 111 by an optional intrinsic region 112. The discrete regions 114 are separated from each other by the first doped region 111 or the intrinsic region 112. The first doped region 111 and the second doped region 113 have opposite types of doping (e.g., region 111 is p-type and region 113 is n-type, or region 111 is n-type and region 113 is p-type). Figure 2B In the example in , each discrete region 114 of the second doped region 113 together with the first doped region 111 and the optional intrinsic region 112 form a diode. Figure 2B In the example of FIG. 1 , the radiation absorbing layer 110 includes a plurality of diodes (more specifically, 7 diodes corresponding to Figure 1 The array has 7 pixels 150 in one row. For simplicity, Figure 2B Only two pixels 150 are marked in FIG. 1 . The plurality of diodes have an electrical contact 119A as a shared (common) electrode. The first doped region 111 may also have discrete portions.

[0065] The electronic layer 120 may include an electronic system 121 suitable for processing or interpreting signals generated by radiation incident on the radiation absorbing layer 110. The electronic system 121 may include analog circuits such as filter networks, amplifiers, integrators, comparators, or digital circuits such as microprocessors and memory. The electronic system 121 may include one or more ADCs. The electronic system 121 may include components shared by the pixels 150 or components dedicated to a single pixel 150. For example, the electronic system 121 may include an amplifier dedicated to each pixel 150 and a microprocessor shared among all pixels 150. The electronic system 121 may be electrically connected to the pixel 150 via a through hole 131. The space between the through holes may be filled with a filling material 130, which may increase the mechanical stability of the connection between the electronic layer 120 and the radiation absorbing layer 110. Other bonding technologies may connect the electronic system 121 to the pixel 150 without using the through hole 131.

[0066] When radiation from the radiation source (not shown) strikes the radiation absorbing layer 110 including the diode, the radiation particle may be absorbed and generate one or more carriers (e.g., electrons and holes) through several mechanisms. The carriers may drift toward one of the electrodes of the diode under an electric field. The electric field may be an external electric field. The electrical contact 119B may include discrete portions, each of which is in electrical contact with the discrete region 114. The term "electrical contact" may be used interchangeably with the term "electrode". In an embodiment, the carriers may drift in different directions so that the carriers generated by a single radiation particle are not substantially shared by two different discrete regions 114 ("substantially not shared" here means that less than 2%, less than 0.5%, less than 0.1%, or less than 0.01% of these carriers flow to a discrete region 114 different from the remaining carriers). The carriers generated by the radiation particles incident around the footprint of one of the discrete regions 114 are not substantially shared by another discrete region 114. A pixel 150 associated with a discrete region 114 may be a region around the discrete region 114 into which substantially all (more than 98%, more than 99.5%, more than 99.9%, or more than 99.99%) of the charge carriers generated by a radiation particle incident therein flow. That is, less than 2%, less than 1%, less than 0.1%, or less than 0.01% of the charge carriers flow outside the pixel 150.

[0067] Figure 2C Schematically illustrating the Figure 1 An alternative detailed cross-sectional view of the image sensor 100 along line 2A-2A. More specifically, the radiation absorbing layer 110 may include a resistor of a semiconductor material such as silicon, germanium, GaAs, CdTe, CdZnTe, or a combination thereof, but not a diode. The semiconductor material may have a high mass attenuation coefficient for the radiation of interest. In an embodiment, Figure 2C The electronic layer 120 in the structure and function is similar to Figure 2B The electronic layer 120 in.

[0068] When the radiation strikes the radiation absorbing layer 110 including the resistor but not the diode, the radiation may be absorbed and generate one or more carriers through several mechanisms. One radiation particle may generate 10 to 100,000 carriers. The carriers may drift toward the electrical contact 119A and the electrical contact 119B under an electric field. The electric field may be an external electric field. The electrical contact 119B includes discrete portions. In an embodiment, the carriers may drift in different directions so that the carriers generated by a single radiation particle are substantially not shared by two different discrete portions of the electrical contact 119B ("substantially not shared" here means that less than 2%, less than 0.5%, less than 0.1% or less than 0.01% of these carriers flow to a discrete portion that is different from the remaining carriers). The carriers generated by the radiation particles incident around the footprint of one of the discrete portions of the electrical contact 119B are substantially not shared by another discrete portion of the electrical contact 119B. A pixel 150 associated with one of the discrete portions of the electrical contact 119B may be a region around the discrete portion into which substantially all (more than 98%, more than 99.5%, more than 99.9%, or more than 99.99%) of the charge carriers generated by radiation particles incident therein flow. That is, less than 2%, less than 0.5%, less than 0.1%, or less than 0.01% of the charge carriers flow outside the pixel associated with one of the discrete portions of the electrical contact 119B.

[0069] Figure 3A Schematically shows a cross-sectional view of a radiation detector 300 according to an embodiment. Specifically, the radiation detector 300 includes a scintillation and reflection layer 310 and Figure 2B or Figure 2C For simplicity, only the pixel 150, the radiation absorption layer 110 and the electronic layer 120 of the image sensor 100 are shown hereinafter, while other components of the image sensor 100 (eg, electrical contacts 119A, 119B, through hole 131) are not shown.

[0070] In an embodiment, the scintillation and reflective layer 310 includes a substrate 312, a reflector 314, and a scintillator 316. The substrate 312 may not be opaque to the radiation of interest 320 (e.g., the radiation 320 may partially attenuate or pass through the substrate 312 substantially without attenuation). For example, the substrate 312 may include silicon.

[0071] In an embodiment, each scintillator 316 may be completely or almost completely surrounded (i.e., substantially completely surrounded) by the pixel 150 and the reflector 314. When the scintillator 316 is exposed to the radiation 320, the scintillator 316 may emit photons. The photons may be emitted in multiple directions (e.g., all directions). In an embodiment, the scintillator 316 may include a material such as sodium iodide (NaI). In an embodiment, the scintillator 316 may include quantum dots. The material of the quantum dots may be cadmium selenide (CdSe), cadmium telluride (CdTe), zinc oxide (ZnO), or any combination of these substances.

[0072] In one embodiment, the material and thickness 314′ of each reflector 314 are such that each reflector 314 is not opaque to the radiation 320, but substantially reflects toward it all photons emitted by the scintillator 316 enclosed therein. For example, each reflector 314 may include aluminum, silver, gold, copper, and any combination thereof; each reflector 314 may have the material and thickness 314′ of approximately 10 micrometers (μm).

[0073] Figure 3B Schematically illustrates a perspective view of a pixel 150 and its associated reflector 314 and scintillator 316 according to an embodiment. Figure 3B As shown, the scintillator 316 is completely surrounded by the pixels 150 and the associated reflectors 314 .

[0074] In the embodiments, reference Figure 3A and Figure 3B , the operation of the radiation detector 300 may be as follows. Specifically, the radiation detector 300 is exposed to the radiation 320 (such as X-rays, gamma rays, etc.) from an object 330 (e.g., a human body part). The radiation 320 may have previously penetrated or scattered from the object 330, and thus carries information about the object 330.

[0075] Because the substrate 312 and the reflector 314 are not opaque to the radiation 320, each scintillator 316 is exposed to the radiation 320 and thereby emits a photon. The photons may be emitted in multiple directions (eg, all directions).

[0076] Each reflector 314 reflects photons incident thereon. Because each scintillator 316 is substantially completely surrounded by the associated reflector 314 and the associated pixel 150 as described above, each photon emitted by the scintillator 316 can enter the pixel 150 without interacting with the reflector 314 or being reflected one or more times by the reflector 314 before entering the pixel 150. In other words, the reflector 314 prevents substantially all (i.e., all or nearly all) of the photons emitted by the scintillator 316 from entering the pixel 150. That is, the reflector 314 directs substantially all (i.e., all or nearly all) of the photons emitted by the scintillator 316 into the pixel 150.

[0077] Figure 3C 1 shows how the reflector 314 according to an embodiment directs photons emitted by the associated scintillator 316 into the associated pixel 150. Specifically, in a first example, a first radiation particle may follow a path d1 toward the pixel 150. At point A, without any reflection from the reflector 314, the first radiation particle may interact with the scintillator 316 and result in the emission of a first photon, which may enter the pixel 150 along a path d1′. In a second example, a second radiation particle may follow a path d2 toward the pixel 150. At point B, the second radiation particle may interact with the scintillator 316 and result in the emission of a second photon, which may follow a path B-B1, be reflected by the reflector 314 at point B1, and then enter the pixel 150 along a path d2′. In a third example, a third radiation particle may follow a path d3 toward the pixel 150. At point C, the third radiation particle may interact with the scintillator 316 and cause emission of a third photon, which may follow path C-C1, be reflected by the reflector 314 at point C1 along path C1-C2, then be reflected again by the reflector 314 at point C2, and then enter the pixel 150 along path d3′. Other paths are also possible.

[0078] The operation of the radiation detector 300 can be restated as follows. The radiation 320 that may have penetrated or scattered from the object 330 now penetrates the substrate 312 and the reflector 314 and is converted into photons by the scintillator 316. Substantially all of the photons are directed by the reflector 314 into the pixels 150 associated with the scintillator 316. In this way, the image of the object 330 captured by the image sensor 100 has negligible crosstalk between the pixels 150 and less loss of photons. Pixel crosstalk occurs when photons emitted by a single particle of the radiation 320 enter more than one pixel 150.

[0079] Figure 4A-4H Schematically illustrating the Figure 3A Specifically, refer to the manufacturing process of the radiation detector 300. Figure 4A The manufacturing process starts with the substrate 312 having a top surface 312s. Next, a template 410 having holes 410a is positioned on the top surface 312s of the substrate 312. In an embodiment, the template 410 may be made of metal. The template 410 may be replaced by a pattern formed with a resist.

[0080] Figure 4B According to the embodiment Figure 4A The top view of the structure, and Figure 4A Shown along line 4A-4A Figure 4B A cross-sectional view of the structure. Figure 4B In the embodiment, a portion of the top surface 312s of the substrate 312 is exposed through the hole 410a in the template 410.

[0081] Next, refer to Figure 4C , the template 410 can be used as a mask for etching the substrate 312, thereby forming a recess 420 in the top surface 312s of the substrate 312. In an embodiment, the etching of the substrate 312 can be anisotropic wet etching using potassium hydroxide (KOH) as an etchant. If the substrate 312 is a silicon substrate and the top surface 312s is a (100) silicon crystal plane, the resulting recess 420, such as Figure 4C As shown, a truncated pyramid shape may be provided with flat and angled etched walls.

[0082] Next, the template 410 may be removed, thereby obtaining Figure 4D Next, refer to Figure 4E The reflector 314 is formed on the wall (eg, side wall and bottom wall) of the recess 420 (also on the Figure 3AIn an embodiment, the reflector 314 may be formed by (a) depositing an aluminum layer (e.g., by thermal evaporation, sputtering, or other suitable technique) onto the Figure 4D , and then (b) polishing back until the top surface 312s of the substrate 312 is exposed to the surrounding environment.

[0083] Alternatively, you can Figure 4C A layer of aluminum is deposited on the structure and then the template 410 is removed to form the reflector 314.

[0084] Next, refer to Figure 4F , a scintillator layer 316t is formed on the top surface 312s and the reflector 314. In an embodiment, the scintillator layer 316t may be formed by depositing a compound including NaI on the top surface 312s and the reflector 314.

[0085] Next, the top surface 316s of the scintillator layer 316t may be polished until the top surface 312s of the substrate 312 is exposed to the surrounding environment, so that Figure 4G As shown, the scintillator 316 is produced. Also as a result, the scintillator and reflective layer 310 is formed.

[0086] Next, if Figure 4H As shown, the scintillation and reflection layer 310 is bonded to the image sensor 100, thereby obtaining Figure 3A The radiation detector 300. In an embodiment, the bonding may be direct bonding, which is a wafer bonding process without any additional intermediate layers (e.g., solder bumps). The bonding process is based on a chemical bond between two surfaces. Direct bonding may be performed at high temperature, but does not necessarily have to be so.

[0087] In the above embodiments, reference Figure 3A , the substrate 312 may include silicon or other suitable materials.

[0088] In the above-described embodiment, the reflector 314 includes aluminum. In alternative embodiments, the reflector 314 may include another metal, such as silver, gold, copper, and any combination thereof.

[0089] In the above embodiments, reference Figure 3A and Figure 3B, each pixel 150 has an associated pair of a reflector 314 and a scintillator 316. In general, each pixel 150 may have N associated pairs of reflectors 314 and scintillators 316 (N is a positive integer) located within the coverage of the pixel 150. In general, for each pixel 150, all or nearly all (i.e., substantially all) photons emitted by the N associated scintillators 316 are guided into the pixel 150 by the N associated reflectors 314.

[0090] In the above embodiments, reference Figure 4E The reflector 314 is formed by (a) Figure 4D A layer of aluminum is deposited on the top of the structure, and then (b) polished back until the top surface 312s of the substrate 312 is exposed to the surrounding environment. In an alternative embodiment, only the above step (a) is performed (i.e., step (b) is not performed), resulting in, Figure 5A As shown, the reflectors 314 are joined to each other.

[0091] Next, the scintillator 316 is formed in the concave portion 420, thereby obtaining Figure 5B The glittering and reflective layer 310'. Figure 5B The formation of the scintillator 316 is similar to Figure 4G The formation of the scintillator 316. Finally, Figure 5C As shown, Figure 5B The scintillation and reflection layer 310 ′ is combined to the image sensor 100 , thereby obtaining a radiation detector 500 .

[0092] Reference Figure 5C , each scintillator 316 is completely enclosed (or nearly completely enclosed) by the associated pixel 150 and the reflector 314 .

[0093] picture Figure 3A Like the radiation detector 300, Figure 5C The radiation detector 500 is also sensitive to the incident radiation 320 . During operation of the radiation detector 500 , all or substantially all of the photons emitted by the scintillator 316 are directed by the reflector 314 into the pixel 150 .

[0094] In the above embodiments, reference Figure 3A and Figure 5CIn the radiation detector 300 and the radiation detector 500, the scintillating and reflective layer 310 / 310′ may be in direct physical contact with the pixel 150 of the image sensor 100. In an alternative embodiment, there may be a sealing layer (not shown) sandwiched between and in direct physical contact with the scintillating and reflective layer 310 / 310′ and the image sensor 100. In this alternative embodiment, the sealing layer may include a material that is transparent or not opaque to the radiation 320, such as a polymer or silicon dioxide. The sealing layer helps to bond the scintillating and reflective layer 310 / 310′ to the image sensor 100. However, due to the presence of the sealing layer, each scintillator 316 is no longer completely surrounded (or almost completely surrounded) by the associated pixel 150 and the associated reflector 314. In an embodiment, the sealing layer should be thin because the thicker the sealing layer, the more photons emitted by the scintillator 316 can escape the associated pixel 150, thereby increasing pixel crosstalk.

[0095] Although various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for illustrative purposes and are not intended to be limiting, and the true scope and spirit of the invention should be determined by the claims herein.

Claims

1. A radiation detector comprising First pixel; first reflector; first scintillator; a first substrate; a second pixel adjacent to the first pixel; A second reflector; and The second scintillator, wherein the first scintillator is in direct physical contact with the first pixel, wherein the first reflector is configured to direct substantially all photons emitted by the first scintillator into the first pixel, wherein the second reflector is configured to direct substantially all photons emitted by the second scintillator into the second pixel, wherein the first reflector is in direct physical contact with the second reflector, The first scintillator is in a recessed portion of a surface of the first substrate. 2 . The radiation detector of claim 1 , wherein the first reflector is in direct physical contact with the first scintillator.

3. The radiation detector of claim 1 , further comprising: a third pixel adjacent to the first pixel; A third reflector; and The third scintillator, Wherein the third reflector is configured to direct substantially all photons emitted by the third scintillator into the third pixel. 4 . The radiation detector of claim 1 , wherein the first reflector is configured to reflect photons emitted by the first scintillator toward the first reflector.

5. The radiation detector of claim 1, wherein the first reflector is not opaque to radiation particles that can cause the first scintillator to emit photons when the radiation particles are incident on the first scintillator. 6 . The radiation detector of claim 1 , wherein the first scintillator is substantially completely surrounded by the first reflector and the first pixel.

7. The radiation detector of claim 1, further comprising: a fourth reflector; and The fourth scintillator, Wherein, the fourth reflector is configured to direct substantially all photons emitted by the fourth scintillator into the first pixel.

8. The radiation detector of claim 1, wherein the first reflector comprises a material selected from the group consisting of aluminum, silver, gold, copper, and any combination thereof.

9. The radiation detector of claim 1, wherein the first scintillator comprises sodium iodide.

10. The radiation detector of claim 1, wherein the first scintillator comprises quantum dots.

11. The radiation detector of claim 1, wherein a portion of the first reflector is disposed on a side wall of the recess.

12. The radiation detector of claim 1, wherein a portion of the first reflector is disposed on an end wall of the recess.

13. The radiation detector of claim 1, wherein the recess has a truncated cone shape.

14. The radiation detector of claim 1, wherein the first substrate comprises silicon or silicon dioxide.

15. The radiation detector of claim 1, further comprising a second substrate, wherein the first pixel is in the second substrate. 16 . The radiation detector of claim 15 , further comprising a sealing layer disposed between the first substrate and the second substrate, wherein the sealing layer is not opaque to photons emitted by the first scintillator.

17. A method of operating a radiation detector, comprising: exposing a first scintillator of the radiation detector to a first radiation particle, thereby causing emission of a first photon from the first scintillator; directing substantially all photons emitted by the first scintillator into a first pixel of the radiation detector using a first reflector of the radiation detector; exposing a second scintillator of the radiation detector to second radiation particles, thereby causing emission of second photons from the second scintillator; as well as directing substantially all of the photons emitted by the second scintillator into a second pixel of the radiation detector using a second reflector of the radiation detector, wherein the second pixel is adjacent to the first pixel, wherein the first scintillator is in direct physical contact with the first pixel, wherein the first reflector is in direct physical contact with the second reflector, The radiation detector includes a first substrate, and the first scintillator is in a recessed portion of a surface of the first substrate.

18. The method of claim 17, wherein the first reflector is in direct physical contact with the first scintillator.

19. The method of claim 17, further comprising determining a characteristic of the first radiation particle based on the first photon.

20. The method of claim 19, wherein the characteristic is energy of the first radiation particle or radiation flux of the first radiation particle.

21. The method of claim 17, further comprising: exposing a third scintillator of the radiation detector to third radiation particles, thereby causing emission of third photons from the third scintillator; and Substantially all photons emitted by the third scintillator are directed into a third pixel of the radiation detector using a third reflector of the radiation detector, wherein the third pixel is adjacent to the first pixel.

22. The method of claim 17, wherein the directing comprises reflecting photons emitted by the first scintillator toward the first reflector using the first reflector.

23. The method of claim 17, wherein the first reflector is not opaque to the first radiation particles.

24. The method of claim 17, wherein the first scintillator is substantially completely surrounded by the first reflector and the first pixel.

25. The method of claim 17, further comprising: exposing a fourth scintillator of the radiation detector to fourth radiation particles, thereby causing emission of fourth photons from the fourth scintillator; and Substantially all photons emitted by the fourth scintillator are directed into fourth pixels of the radiation detector using a fourth reflector of the radiation detector.

26. The method of claim 17, wherein the first reflector comprises a material selected from the group consisting of aluminum, silver, gold, copper, and any combination thereof.

27. The method of claim 17, wherein the first scintillator comprises quantum dots.

28. The method of claim 17, wherein a portion of the first reflector is disposed on a sidewall of the recess.

29. The method of claim 17, wherein a portion of the first reflector is disposed on an end wall of the recess.

30. The method of claim 17, wherein the recess has a truncated cone shape.

31. The method of claim 17, wherein the first substrate comprises silicon or silicon dioxide.

32. The method of claim 17, wherein the radiation detector further comprises a second substrate, and The first pixel is in the second substrate.

33. The method of claim 32, wherein the radiation detector further comprises a sealing layer disposed between the first substrate and the second substrate, and The sealing layer is not opaque to photons emitted by the first scintillator.

34. A method for forming a radiation detector, comprising: forming a first recess on a surface of the first substrate; forming a first reflector on a wall of the first recess; forming a first scintillator in the first recess; forming a second recess on the surface of the first substrate; forming a second reflector on a wall of the second recess; forming a second scintillator in the second recess; as well as bonding a second substrate having a first pixel and a second pixel to the first substrate, wherein the first reflector is configured to direct substantially all photons emitted by the first scintillator into the first pixel, wherein the second reflector is configured to direct substantially all photons emitted by the second scintillator into the second pixel, wherein the first scintillator is in direct physical contact with the first pixel, Wherein the first reflector is in direct physical contact with the second reflector.

35. The method of claim 34, wherein the first reflector is in direct physical contact with the first scintillator.

36. The method of claim 34, wherein the first reflector is configured to reflect photons emitted by the first scintillator toward the first reflector.

37. The method of claim 34, wherein the first scintillator is substantially completely surrounded by the first reflector and the first pixel.

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