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Title: The dependence of the modulation transfer function on the blocking layer thickness in amorphous selenium x-ray detectors

Abstract

Blocking layers are used to reduce leakage current in amorphous selenium detectors. The effect of the thickness of the blocking layer on the presampling modulation transfer function (MTF) and on dark current was experimentally determined in prototype single-line CCD-based amorphous selenium (a-Se) x-ray detectors. The sampling pitch of the detectors evaluated was 25 {mu}m and the blocking layer thicknesses varied from 1 to 51 {mu}m. The blocking layers resided on the signal collection electrodes which, in this configuration, were used to collect electrons. The combined thickness of the blocking layer and a-Se bulk in each detector was {approx}200 {mu}m. As expected, the dark current increased monotonically as the thickness of the blocking layer was decreased. It was found that if the blocking layer thickness was small compared to the sampling pitch, it caused a negligible reduction in MTF. However, the MTF was observed to decrease dramatically at spatial frequencies near the Nyquist frequency as the blocking layer thickness approached or exceeded the electrode sampling pitch. This observed reduction in MTF is shown to be consistent with predictions of an electrostatic model wherein the image charge from the a-Se is trapped at a characteristic depth within the blocking layer, generally nearmore » the interface between the blocking layer and the a-Se bulk.« less

Authors:
; ; ; ; ; ; ; ; ; ;  [1];  [2];  [2];  [2];  [2];  [2];  [3];  [2];  [3];  [2]
  1. Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, M4N 3M5 (Canada)
  2. (Canada)
  3. (United States)
Publication Date:
OSTI Identifier:
20953511
Resource Type:
Journal Article
Journal Name:
Medical Physics
Additional Journal Information:
Journal Volume: 34; Journal Issue: 8; Other Information: DOI: 10.1118/1.2757002; (c) 2007 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0094-2405
Country of Publication:
United States
Language:
English
Subject:
62 RADIOLOGY AND NUCLEAR MEDICINE; BIOMEDICAL RADIOGRAPHY; CHARGE-COUPLED DEVICES; DEPLETION LAYER; IMAGE PROCESSING; IMAGES; MAMMARY GLANDS; MODULATION; THICKNESS; TRANSFER FUNCTIONS; X-RAY DETECTION

Citation Formats

Hunter, David M., Belev, Gueorgi, DeCrescenzo, Giovanni, Kasap, Safa O., Mainprize, James G., Rowlands, J. A., Smith, Charles, Tuemer, Tuemay, Verpakhovski, Vladimir, Yin Shi, Yaffe, Martin J., Department of Electrical Engineering, University of Saskatchewan, Saskatoon, Saskatchewan, S7N 5A9, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, M4N 3M5, Department of Electrical Engineering, University of Saskatchewan, Saskatoon, Saskatchewan, S7N 5A9, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, M4N 3M5, DALSA Inc., Waterloo, Ontario, N2V 2E9, NOVA R and D, Riverside, California 92507-3429, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, M4N 3M5, NOVA R and D, Riverside, California 92507-3429, and Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, M4N 3M5. The dependence of the modulation transfer function on the blocking layer thickness in amorphous selenium x-ray detectors. United States: N. p., 2007. Web. doi:10.1118/1.2757002.
Hunter, David M., Belev, Gueorgi, DeCrescenzo, Giovanni, Kasap, Safa O., Mainprize, James G., Rowlands, J. A., Smith, Charles, Tuemer, Tuemay, Verpakhovski, Vladimir, Yin Shi, Yaffe, Martin J., Department of Electrical Engineering, University of Saskatchewan, Saskatoon, Saskatchewan, S7N 5A9, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, M4N 3M5, Department of Electrical Engineering, University of Saskatchewan, Saskatoon, Saskatchewan, S7N 5A9, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, M4N 3M5, DALSA Inc., Waterloo, Ontario, N2V 2E9, NOVA R and D, Riverside, California 92507-3429, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, M4N 3M5, NOVA R and D, Riverside, California 92507-3429, & Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, M4N 3M5. The dependence of the modulation transfer function on the blocking layer thickness in amorphous selenium x-ray detectors. United States. doi:10.1118/1.2757002.
Hunter, David M., Belev, Gueorgi, DeCrescenzo, Giovanni, Kasap, Safa O., Mainprize, James G., Rowlands, J. A., Smith, Charles, Tuemer, Tuemay, Verpakhovski, Vladimir, Yin Shi, Yaffe, Martin J., Department of Electrical Engineering, University of Saskatchewan, Saskatoon, Saskatchewan, S7N 5A9, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, M4N 3M5, Department of Electrical Engineering, University of Saskatchewan, Saskatoon, Saskatchewan, S7N 5A9, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, M4N 3M5, DALSA Inc., Waterloo, Ontario, N2V 2E9, NOVA R and D, Riverside, California 92507-3429, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, M4N 3M5, NOVA R and D, Riverside, California 92507-3429, and Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, M4N 3M5. Wed . "The dependence of the modulation transfer function on the blocking layer thickness in amorphous selenium x-ray detectors". United States. doi:10.1118/1.2757002.
@article{osti_20953511,
title = {The dependence of the modulation transfer function on the blocking layer thickness in amorphous selenium x-ray detectors},
author = {Hunter, David M. and Belev, Gueorgi and DeCrescenzo, Giovanni and Kasap, Safa O. and Mainprize, James G. and Rowlands, J. A. and Smith, Charles and Tuemer, Tuemay and Verpakhovski, Vladimir and Yin Shi and Yaffe, Martin J. and Department of Electrical Engineering, University of Saskatchewan, Saskatoon, Saskatchewan, S7N 5A9 and Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, M4N 3M5 and Department of Electrical Engineering, University of Saskatchewan, Saskatoon, Saskatchewan, S7N 5A9 and Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, M4N 3M5 and DALSA Inc., Waterloo, Ontario, N2V 2E9 and NOVA R and D, Riverside, California 92507-3429 and Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, M4N 3M5 and NOVA R and D, Riverside, California 92507-3429 and Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, M4N 3M5},
abstractNote = {Blocking layers are used to reduce leakage current in amorphous selenium detectors. The effect of the thickness of the blocking layer on the presampling modulation transfer function (MTF) and on dark current was experimentally determined in prototype single-line CCD-based amorphous selenium (a-Se) x-ray detectors. The sampling pitch of the detectors evaluated was 25 {mu}m and the blocking layer thicknesses varied from 1 to 51 {mu}m. The blocking layers resided on the signal collection electrodes which, in this configuration, were used to collect electrons. The combined thickness of the blocking layer and a-Se bulk in each detector was {approx}200 {mu}m. As expected, the dark current increased monotonically as the thickness of the blocking layer was decreased. It was found that if the blocking layer thickness was small compared to the sampling pitch, it caused a negligible reduction in MTF. However, the MTF was observed to decrease dramatically at spatial frequencies near the Nyquist frequency as the blocking layer thickness approached or exceeded the electrode sampling pitch. This observed reduction in MTF is shown to be consistent with predictions of an electrostatic model wherein the image charge from the a-Se is trapped at a characteristic depth within the blocking layer, generally near the interface between the blocking layer and the a-Se bulk.},
doi = {10.1118/1.2757002},
journal = {Medical Physics},
issn = {0094-2405},
number = 8,
volume = 34,
place = {United States},
year = {2007},
month = {8}
}