The Experts below are selected from a list of 72 Experts worldwide ranked by ideXlab platform
Israel Koren - One of the best experts on this subject based on the ideXlab platform.
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using Digital Imagers to characterize the dependence of energy and area distributions of seus on elevation
Defect and Fault Tolerance in VLSI and Nanotechnology Systems, 2020Co-Authors: Glenn H Chapman, Rohan Thomas, Israel Koren, J Klinsmann, Zahava KorenAbstract:Camera Integrated circuits (ICs) suffer from soft errors known as Single Event Upsets (SEUs). Unlike traditional ICs, camera sensors record the location and energy deposited by each SEU. Camera pixels measure when and where cosmic ray particles hit and store the deposited charge when dark-frame images are taken. Hence, with large datasets of time-lapsed dark-frame images, pixel analysis provides the intensity and energy distribution of deposited SEU charges, the energy vs occurrence rate, the total area of the charge ball, and potentially the dependence of the number of SEUs on the camera elevation. Previously developed noise distribution analysis enables the removal of noise and the detection of low energy SEUs. In addition, it allows estimating the area of the deposited charge. We used two DSLR cameras and measured SEU rates at elevations from sea level to 1088 m, allowing us to explore the dependence of SEU energy and area distributions on elevation. We observed significant increases in SEUs with elevation changes of < 50 meters.
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detecting seus in noisy Digital Imagers with small pixels
Defect and Fault Tolerance in VLSI and Nanotechnology Systems, 2019Co-Authors: Glenn H Chapman, Rohan Thomas, Israel Koren, J Klinsmann, Coelho Silva Meneses, Bifei Huang, Hao Yang, Zahava KorenAbstract:Camera sensors are susceptible to the same transient (non-permanent) errors that occur in standard Digital semiconductors, known as Single Event Upsets (SEUs). These result from the charge deposited by cosmic ray particles on the semiconductor. In a camera sensor, SEUs manifest themselves as one or more brighter pixels in a dark-frame image during long exposure times. Since the value of brighter pixels is related directly to the deposited charge, SEU analysis of Digital Imagers provides essential information about the nature and amount of charge deposited by particle hits, their occurrence rate, and the charge spread area. In this paper we describe an experimental approach to collect this information from pixels of size of $7\mu\mathbf{m}$ (DSLR cameras) down to $1.2\mu \mathbf{m}$ (cell phone cameras). High gain (ISO) images allow us to detect lower energy SEUs but at the cost of a noisier background. The smaller pixels $(1.2\mu \mathrm{m})$ are more sensitive to lower energy SEUs, but have considerably noisier background levels. It is important to observe the SEU information over a range of gains (ISOs) and pixel sizes, to obtain the energy and spatial distribution of the SEUs, which is valuable for understanding the nature of SEUs in other circuits. The problem is that SEUs, by their transient nature, appear randomly in both time and location in a series of images. It is important to separate those from the noisy imager random excursions above the background level. We implement a new algorithm that is more effective in separating SEUs from random noise by leveraging thousands of images to obtain the noise distribution of each individual pixel.
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single event upsets and hot pixels in Digital Imagers
Defect and Fault Tolerance in VLSI and Nanotechnology Systems, 2015Co-Authors: Glenn H Chapman, Rahul Thomas, Rohan Thomas, Klinsmann Coelho Silva J Meneses, Tommy Q Yang, Israel Koren, Zahava KorenAbstract:From extensive study of Digital imager defects, we found that permanent “Hot Pixels” are the main long term Digital camera defects, and are caused by high energy cosmic ray particles. Clearly, as in other microelectronic integrated circuits, most of the particles do not induce permanent damage but instead, inject a short term charge that may cause a transient fault, known as a Single Event Upset (SEU). Unlike standard Digital ICs, pixels in a Digital imaging sensor can be monitored at almost any desirable frequency. Since an SEU manifests itself as one or more brighter pixels in an otherwise dark image, the rate of SEUs can be measured at a considerably higher accuracy by taking dark-field pictures at different exposure times and different frequencies. In this paper we describe an experimental approach to measuring the occurrence rate and resulting characteristics of SEUs. The SEU rate that we have observed for Digital Imagers, of about 4 SEUs for every 30 seconds, is considerably higher than was previously reported for ordinary ICs. For the same imager, permanent hot pixels have a rate of 1 every 12.6 days, while SEUs occur 145,000 times more often. Ordinary IC SEU rates have been reported to be about 100× of permanent fault rates. In addition, we found that some SEUs in Digital Imagers do not impact a single pixel, as do hot pixels, but can create a line of injected charges which appears as a bright line in the dark image.
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enhanced correction methods for high density hot pixel defects in Digital Imagers
electronic imaging, 2015Co-Authors: Glenn H Chapman, Rahul Thomas, Zahava Koren, Rohit Thomas, Israel KorenAbstract:Our previous research has found that the main defects in Digital cameras are “Hot Pixels” which increase at a nearly constant temporal rate. Defect rates have been shown to grow as a power law of the pixel size and ISO, potentially causing hundreds to thousands of defects per year in cameras with <2 micron pixels, thus making image correction crucial. This paper discusses a novel correction method that uses a weighted combination of two terms - traditional interpolation and hot pixel parameters correction. The weights are based on defect severity, ISO, exposure time and complexity of the image. For the hot pixel parameters component, we have studied the behavior of hot pixels under illumination and have created a new correction model that takes this behavior into account. We show that for an image with a slowly changing background, the classic interpolation performs well. However, for more complex scenes, the correction improves when a weighted combination of both components is used. To test our algorithm’s accuracy, we devised a novel laboratory experimental method for extracting the true value of the pixel that currently experiences a hot pixel defect. This method involves a simple translation of the imager based on the pixel size and other optical distances.
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improved correction for hot pixels in Digital Imagers
Defect and Fault Tolerance in VLSI and Nanotechnology Systems, 2014Co-Authors: Glenn H Chapman, Rahul Thomas, Israel Koren, Rohit Thomas, Zahava KorenAbstract:From extensive study of Digital imager defects, we found that “Hot Pixels” are the main Digital camera defects, and that they increase at a nearly constant temporal rate over the camera's lifetime. Previously we characterized the hot pixels by a linear function of the exposure time in response to a dark frame setting. Using a camera with 55 known hot pixels, we compared our hot pixel correction algorithm to a conventional 4-nearest neighbor interpolation techniques. We developed a new “moving camera” method to exactly obtain both the actual hot pixel contribution and the true undamaged pixel value at a defect. Using these calibrated results we find that the correction method should be based on the hot pixel severity, the illumination intensity at the pixel, camera parameters such as ISO and exposure time, and on the neighboring pixels' variability.
Zahava Koren - One of the best experts on this subject based on the ideXlab platform.
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using Digital Imagers to characterize the dependence of energy and area distributions of seus on elevation
Defect and Fault Tolerance in VLSI and Nanotechnology Systems, 2020Co-Authors: Glenn H Chapman, Rohan Thomas, Israel Koren, J Klinsmann, Zahava KorenAbstract:Camera Integrated circuits (ICs) suffer from soft errors known as Single Event Upsets (SEUs). Unlike traditional ICs, camera sensors record the location and energy deposited by each SEU. Camera pixels measure when and where cosmic ray particles hit and store the deposited charge when dark-frame images are taken. Hence, with large datasets of time-lapsed dark-frame images, pixel analysis provides the intensity and energy distribution of deposited SEU charges, the energy vs occurrence rate, the total area of the charge ball, and potentially the dependence of the number of SEUs on the camera elevation. Previously developed noise distribution analysis enables the removal of noise and the detection of low energy SEUs. In addition, it allows estimating the area of the deposited charge. We used two DSLR cameras and measured SEU rates at elevations from sea level to 1088 m, allowing us to explore the dependence of SEU energy and area distributions on elevation. We observed significant increases in SEUs with elevation changes of < 50 meters.
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detecting seus in noisy Digital Imagers with small pixels
Defect and Fault Tolerance in VLSI and Nanotechnology Systems, 2019Co-Authors: Glenn H Chapman, Rohan Thomas, Israel Koren, J Klinsmann, Coelho Silva Meneses, Bifei Huang, Hao Yang, Zahava KorenAbstract:Camera sensors are susceptible to the same transient (non-permanent) errors that occur in standard Digital semiconductors, known as Single Event Upsets (SEUs). These result from the charge deposited by cosmic ray particles on the semiconductor. In a camera sensor, SEUs manifest themselves as one or more brighter pixels in a dark-frame image during long exposure times. Since the value of brighter pixels is related directly to the deposited charge, SEU analysis of Digital Imagers provides essential information about the nature and amount of charge deposited by particle hits, their occurrence rate, and the charge spread area. In this paper we describe an experimental approach to collect this information from pixels of size of $7\mu\mathbf{m}$ (DSLR cameras) down to $1.2\mu \mathbf{m}$ (cell phone cameras). High gain (ISO) images allow us to detect lower energy SEUs but at the cost of a noisier background. The smaller pixels $(1.2\mu \mathrm{m})$ are more sensitive to lower energy SEUs, but have considerably noisier background levels. It is important to observe the SEU information over a range of gains (ISOs) and pixel sizes, to obtain the energy and spatial distribution of the SEUs, which is valuable for understanding the nature of SEUs in other circuits. The problem is that SEUs, by their transient nature, appear randomly in both time and location in a series of images. It is important to separate those from the noisy imager random excursions above the background level. We implement a new algorithm that is more effective in separating SEUs from random noise by leveraging thousands of images to obtain the noise distribution of each individual pixel.
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single event upsets and hot pixels in Digital Imagers
Defect and Fault Tolerance in VLSI and Nanotechnology Systems, 2015Co-Authors: Glenn H Chapman, Rahul Thomas, Rohan Thomas, Klinsmann Coelho Silva J Meneses, Tommy Q Yang, Israel Koren, Zahava KorenAbstract:From extensive study of Digital imager defects, we found that permanent “Hot Pixels” are the main long term Digital camera defects, and are caused by high energy cosmic ray particles. Clearly, as in other microelectronic integrated circuits, most of the particles do not induce permanent damage but instead, inject a short term charge that may cause a transient fault, known as a Single Event Upset (SEU). Unlike standard Digital ICs, pixels in a Digital imaging sensor can be monitored at almost any desirable frequency. Since an SEU manifests itself as one or more brighter pixels in an otherwise dark image, the rate of SEUs can be measured at a considerably higher accuracy by taking dark-field pictures at different exposure times and different frequencies. In this paper we describe an experimental approach to measuring the occurrence rate and resulting characteristics of SEUs. The SEU rate that we have observed for Digital Imagers, of about 4 SEUs for every 30 seconds, is considerably higher than was previously reported for ordinary ICs. For the same imager, permanent hot pixels have a rate of 1 every 12.6 days, while SEUs occur 145,000 times more often. Ordinary IC SEU rates have been reported to be about 100× of permanent fault rates. In addition, we found that some SEUs in Digital Imagers do not impact a single pixel, as do hot pixels, but can create a line of injected charges which appears as a bright line in the dark image.
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enhanced correction methods for high density hot pixel defects in Digital Imagers
electronic imaging, 2015Co-Authors: Glenn H Chapman, Rahul Thomas, Zahava Koren, Rohit Thomas, Israel KorenAbstract:Our previous research has found that the main defects in Digital cameras are “Hot Pixels” which increase at a nearly constant temporal rate. Defect rates have been shown to grow as a power law of the pixel size and ISO, potentially causing hundreds to thousands of defects per year in cameras with <2 micron pixels, thus making image correction crucial. This paper discusses a novel correction method that uses a weighted combination of two terms - traditional interpolation and hot pixel parameters correction. The weights are based on defect severity, ISO, exposure time and complexity of the image. For the hot pixel parameters component, we have studied the behavior of hot pixels under illumination and have created a new correction model that takes this behavior into account. We show that for an image with a slowly changing background, the classic interpolation performs well. However, for more complex scenes, the correction improves when a weighted combination of both components is used. To test our algorithm’s accuracy, we devised a novel laboratory experimental method for extracting the true value of the pixel that currently experiences a hot pixel defect. This method involves a simple translation of the imager based on the pixel size and other optical distances.
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improved correction for hot pixels in Digital Imagers
Defect and Fault Tolerance in VLSI and Nanotechnology Systems, 2014Co-Authors: Glenn H Chapman, Rahul Thomas, Israel Koren, Rohit Thomas, Zahava KorenAbstract:From extensive study of Digital imager defects, we found that “Hot Pixels” are the main Digital camera defects, and that they increase at a nearly constant temporal rate over the camera's lifetime. Previously we characterized the hot pixels by a linear function of the exposure time in response to a dark frame setting. Using a camera with 55 known hot pixels, we compared our hot pixel correction algorithm to a conventional 4-nearest neighbor interpolation techniques. We developed a new “moving camera” method to exactly obtain both the actual hot pixel contribution and the true undamaged pixel value at a defect. Using these calibrated results we find that the correction method should be based on the hot pixel severity, the illumination intensity at the pixel, camera parameters such as ISO and exposure time, and on the neighboring pixels' variability.
Glenn H Chapman - One of the best experts on this subject based on the ideXlab platform.
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using Digital Imagers to characterize the dependence of energy and area distributions of seus on elevation
Defect and Fault Tolerance in VLSI and Nanotechnology Systems, 2020Co-Authors: Glenn H Chapman, Rohan Thomas, Israel Koren, J Klinsmann, Zahava KorenAbstract:Camera Integrated circuits (ICs) suffer from soft errors known as Single Event Upsets (SEUs). Unlike traditional ICs, camera sensors record the location and energy deposited by each SEU. Camera pixels measure when and where cosmic ray particles hit and store the deposited charge when dark-frame images are taken. Hence, with large datasets of time-lapsed dark-frame images, pixel analysis provides the intensity and energy distribution of deposited SEU charges, the energy vs occurrence rate, the total area of the charge ball, and potentially the dependence of the number of SEUs on the camera elevation. Previously developed noise distribution analysis enables the removal of noise and the detection of low energy SEUs. In addition, it allows estimating the area of the deposited charge. We used two DSLR cameras and measured SEU rates at elevations from sea level to 1088 m, allowing us to explore the dependence of SEU energy and area distributions on elevation. We observed significant increases in SEUs with elevation changes of < 50 meters.
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detecting seus in noisy Digital Imagers with small pixels
Defect and Fault Tolerance in VLSI and Nanotechnology Systems, 2019Co-Authors: Glenn H Chapman, Rohan Thomas, Israel Koren, J Klinsmann, Coelho Silva Meneses, Bifei Huang, Hao Yang, Zahava KorenAbstract:Camera sensors are susceptible to the same transient (non-permanent) errors that occur in standard Digital semiconductors, known as Single Event Upsets (SEUs). These result from the charge deposited by cosmic ray particles on the semiconductor. In a camera sensor, SEUs manifest themselves as one or more brighter pixels in a dark-frame image during long exposure times. Since the value of brighter pixels is related directly to the deposited charge, SEU analysis of Digital Imagers provides essential information about the nature and amount of charge deposited by particle hits, their occurrence rate, and the charge spread area. In this paper we describe an experimental approach to collect this information from pixels of size of $7\mu\mathbf{m}$ (DSLR cameras) down to $1.2\mu \mathbf{m}$ (cell phone cameras). High gain (ISO) images allow us to detect lower energy SEUs but at the cost of a noisier background. The smaller pixels $(1.2\mu \mathrm{m})$ are more sensitive to lower energy SEUs, but have considerably noisier background levels. It is important to observe the SEU information over a range of gains (ISOs) and pixel sizes, to obtain the energy and spatial distribution of the SEUs, which is valuable for understanding the nature of SEUs in other circuits. The problem is that SEUs, by their transient nature, appear randomly in both time and location in a series of images. It is important to separate those from the noisy imager random excursions above the background level. We implement a new algorithm that is more effective in separating SEUs from random noise by leveraging thousands of images to obtain the noise distribution of each individual pixel.
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single event upsets and hot pixels in Digital Imagers
Defect and Fault Tolerance in VLSI and Nanotechnology Systems, 2015Co-Authors: Glenn H Chapman, Rahul Thomas, Rohan Thomas, Klinsmann Coelho Silva J Meneses, Tommy Q Yang, Israel Koren, Zahava KorenAbstract:From extensive study of Digital imager defects, we found that permanent “Hot Pixels” are the main long term Digital camera defects, and are caused by high energy cosmic ray particles. Clearly, as in other microelectronic integrated circuits, most of the particles do not induce permanent damage but instead, inject a short term charge that may cause a transient fault, known as a Single Event Upset (SEU). Unlike standard Digital ICs, pixels in a Digital imaging sensor can be monitored at almost any desirable frequency. Since an SEU manifests itself as one or more brighter pixels in an otherwise dark image, the rate of SEUs can be measured at a considerably higher accuracy by taking dark-field pictures at different exposure times and different frequencies. In this paper we describe an experimental approach to measuring the occurrence rate and resulting characteristics of SEUs. The SEU rate that we have observed for Digital Imagers, of about 4 SEUs for every 30 seconds, is considerably higher than was previously reported for ordinary ICs. For the same imager, permanent hot pixels have a rate of 1 every 12.6 days, while SEUs occur 145,000 times more often. Ordinary IC SEU rates have been reported to be about 100× of permanent fault rates. In addition, we found that some SEUs in Digital Imagers do not impact a single pixel, as do hot pixels, but can create a line of injected charges which appears as a bright line in the dark image.
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enhanced correction methods for high density hot pixel defects in Digital Imagers
electronic imaging, 2015Co-Authors: Glenn H Chapman, Rahul Thomas, Zahava Koren, Rohit Thomas, Israel KorenAbstract:Our previous research has found that the main defects in Digital cameras are “Hot Pixels” which increase at a nearly constant temporal rate. Defect rates have been shown to grow as a power law of the pixel size and ISO, potentially causing hundreds to thousands of defects per year in cameras with <2 micron pixels, thus making image correction crucial. This paper discusses a novel correction method that uses a weighted combination of two terms - traditional interpolation and hot pixel parameters correction. The weights are based on defect severity, ISO, exposure time and complexity of the image. For the hot pixel parameters component, we have studied the behavior of hot pixels under illumination and have created a new correction model that takes this behavior into account. We show that for an image with a slowly changing background, the classic interpolation performs well. However, for more complex scenes, the correction improves when a weighted combination of both components is used. To test our algorithm’s accuracy, we devised a novel laboratory experimental method for extracting the true value of the pixel that currently experiences a hot pixel defect. This method involves a simple translation of the imager based on the pixel size and other optical distances.
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improved correction for hot pixels in Digital Imagers
Defect and Fault Tolerance in VLSI and Nanotechnology Systems, 2014Co-Authors: Glenn H Chapman, Rahul Thomas, Israel Koren, Rohit Thomas, Zahava KorenAbstract:From extensive study of Digital imager defects, we found that “Hot Pixels” are the main Digital camera defects, and that they increase at a nearly constant temporal rate over the camera's lifetime. Previously we characterized the hot pixels by a linear function of the exposure time in response to a dark frame setting. Using a camera with 55 known hot pixels, we compared our hot pixel correction algorithm to a conventional 4-nearest neighbor interpolation techniques. We developed a new “moving camera” method to exactly obtain both the actual hot pixel contribution and the true undamaged pixel value at a defect. Using these calibrated results we find that the correction method should be based on the hot pixel severity, the illumination intensity at the pixel, camera parameters such as ISO and exposure time, and on the neighboring pixels' variability.
L Fornaro - One of the best experts on this subject based on the ideXlab platform.
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bismuth tri iodide polycrystalline films for x ray direct and Digital Imagers
Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment, 2009Co-Authors: I Aguiar, S Kroger, L FornaroAbstract:Abstract Bismuth tri-iodide films were grown by the physical vapor deposition method on gold-coated glass substrates 1 in.×1 in. (2.5×2.5 cm) in size. The growth was performed in a system especially designed and constructed for getting a fine control of the growth parameters. The best growth conditions were a source temperature of 350 °C, a growth temperature of 175 °C and a growth time of 24 h, with an initial pressure of 3×10 −2 Pa. Film thicknesses and grain sizes gave values ranging between 5 and 60 μm (10%), and between 0.5 and 2 μm, respectively. The dark current density of the films is 9.7 pA/mm 2 for an electric field of 5.6 V/μm, and the resistivity is 1.4×10 13 Ω cm. Mobility-lifetime values of 3×10 −7 cm 2 /V can be estimated for electrons. A signal to dark relation of 2.3 was measured at 250 mA and 40 KVp, with an electric field of 1 V/μm applied to the film.
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low dark current 00l mercuric iodide thick films for x ray direct and Digital Imagers
IEEE Transactions on Nuclear Science, 2005Co-Authors: L Fornaro, I Aguiar, A Cuna, A Noguera, M Perez, L Mussio, A GancharovAbstract:Mercuric iodide films were grown by the physical vapor deposition method on palladium-coated glass substrates 2''times2'' in size. The growth was performed in a system especially designed and constructed for getting a fine control of the growth parameters. The best growth conditions were a source temperature of 120degC, a growth temperature of 60degC and a growth time of 24 h, with an initial pressure of 6times10-3 Pa. Film thicknesses and grain sizes gave values ranging between 100 and 260 mum (10%), and between (10plusmn5) and (30plusmn10) mum, respectively. Films grew oriented with the (00l) crystalline planes parallel to the substrate, with a texture of 0.94, measured by X-ray powder diffraction. The dark current density of the films is lower than 0.3 pA/mm2 for electric fields below 0.4 V/mum, and their resistivity is 1.5times1014 Omega.cm. Mobility-lifetime values of 5.2times10-6 cm2/V and 6.2times10-6 cm2/V can be estimated for electrons and holes, respectively. Films give a sensitivity to X-rays of 37 nC/R.cm2. A signal to dark relation of 1120 was measured at 750 mR/s and 32 KVp, with an electric field of 0.4 V/mum applied to the film. The low dark current, as far as the high signal to noise results obtained, indicate these films as very suitable for direct and Digital imaging
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low dark current 00l mercuric iodide thick films for x ray direct and Digital Imagers
IEEE Symposium Conference Record Nuclear Science 2004., 2004Co-Authors: L Fornaro, I Aguiar, A Cuna, A Noguera, M Perez, L Mussio, A GancharovAbstract:Mercuric iodide films were grown by the physical vapor deposition method on palladium-coated glass substrates 2"/spl times/2" in size. The growth was performed in a system especially designed and constructed for getting a fine control of the growth parameters. The best growth conditions were a source temperature of 120/spl deg/C, a growth temperature of 60/spl deg/C and a growth time of 48 hours, with an initial pressure of 6/spl times/10-/sup 3/ Pa. Film thicknesses and grain sizes gave values ranging between 100 and 260 /spl mu/m (10%), and between 10 and 30 /spl mu/m, respectively. Films grow oriented with the (00l) crystalline planes parallel to the substrate, with a texture of 0.94, measured by X-ray powder diffraction. The dark current density of the films is lower than 0.3 pA/mm/sup 2/ for electric fields below 0.4 V//spl mu/m, and their resistivity is 1.5/spl times/10/sup 14/ /spl Omega/cm. Mobility-lifetime values of 2/spl times/10-5 cm/sup 2//V and 5/spl times/10-5 cm/sup 2//V can be estimated for electrons and holes respectively. Films give a sensitivity to X-rays of 37 nC/R.cm/sup 2/. A signal to dark relation of 1120 was measured at 750 mR/s and 32 KVp, with an electric field of 0.4 V//spl mu/m applied to the film. The low dark current, as far as the high signal to noise results obtained, are attributed to the high texture of the films and to the charge transport along the c axis.
A Gancharov - One of the best experts on this subject based on the ideXlab platform.
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low dark current 00l mercuric iodide thick films for x ray direct and Digital Imagers
IEEE Transactions on Nuclear Science, 2005Co-Authors: L Fornaro, I Aguiar, A Cuna, A Noguera, M Perez, L Mussio, A GancharovAbstract:Mercuric iodide films were grown by the physical vapor deposition method on palladium-coated glass substrates 2''times2'' in size. The growth was performed in a system especially designed and constructed for getting a fine control of the growth parameters. The best growth conditions were a source temperature of 120degC, a growth temperature of 60degC and a growth time of 24 h, with an initial pressure of 6times10-3 Pa. Film thicknesses and grain sizes gave values ranging between 100 and 260 mum (10%), and between (10plusmn5) and (30plusmn10) mum, respectively. Films grew oriented with the (00l) crystalline planes parallel to the substrate, with a texture of 0.94, measured by X-ray powder diffraction. The dark current density of the films is lower than 0.3 pA/mm2 for electric fields below 0.4 V/mum, and their resistivity is 1.5times1014 Omega.cm. Mobility-lifetime values of 5.2times10-6 cm2/V and 6.2times10-6 cm2/V can be estimated for electrons and holes, respectively. Films give a sensitivity to X-rays of 37 nC/R.cm2. A signal to dark relation of 1120 was measured at 750 mR/s and 32 KVp, with an electric field of 0.4 V/mum applied to the film. The low dark current, as far as the high signal to noise results obtained, indicate these films as very suitable for direct and Digital imaging
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low dark current 00l mercuric iodide thick films for x ray direct and Digital Imagers
IEEE Symposium Conference Record Nuclear Science 2004., 2004Co-Authors: L Fornaro, I Aguiar, A Cuna, A Noguera, M Perez, L Mussio, A GancharovAbstract:Mercuric iodide films were grown by the physical vapor deposition method on palladium-coated glass substrates 2"/spl times/2" in size. The growth was performed in a system especially designed and constructed for getting a fine control of the growth parameters. The best growth conditions were a source temperature of 120/spl deg/C, a growth temperature of 60/spl deg/C and a growth time of 48 hours, with an initial pressure of 6/spl times/10-/sup 3/ Pa. Film thicknesses and grain sizes gave values ranging between 100 and 260 /spl mu/m (10%), and between 10 and 30 /spl mu/m, respectively. Films grow oriented with the (00l) crystalline planes parallel to the substrate, with a texture of 0.94, measured by X-ray powder diffraction. The dark current density of the films is lower than 0.3 pA/mm/sup 2/ for electric fields below 0.4 V//spl mu/m, and their resistivity is 1.5/spl times/10/sup 14/ /spl Omega/cm. Mobility-lifetime values of 2/spl times/10-5 cm/sup 2//V and 5/spl times/10-5 cm/sup 2//V can be estimated for electrons and holes respectively. Films give a sensitivity to X-rays of 37 nC/R.cm/sup 2/. A signal to dark relation of 1120 was measured at 750 mR/s and 32 KVp, with an electric field of 0.4 V//spl mu/m applied to the film. The low dark current, as far as the high signal to noise results obtained, are attributed to the high texture of the films and to the charge transport along the c axis.