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Proceedings Paper

Improved properties of PbI2 x-ray imagers with tighter process control and using positive bias voltage
Author(s): George Zentai; Larry Partain; Raisa Pavlyuchkova; Cesar Proano; Gary F. Virshup; Paul Bennett; Kanai Shah; Yuri Dmitriev; Jerry Thomas
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Paper Abstract

Vapor deposited lead iodide films show a wide range of physical attributes dependant upon fabrication conditions. High density is most readily achieved with films less than 100 μm. Thicker films, with lessening density, often show lower response (gain) as charge collection becomes less efficient. Lack of consistency in density throughout a deposition invariably leads to non-uniform electronic properties, which is challenging to both model and predict. To overcome this, tighter control of deposition parameters is required during the slow growth process (<10 μm/hour). Lead iodide films are characterized in forms of planar devices deposited onto conductive glass and active pixel arrays deposited onto a-Si TFT arrays1. Electronic properties (e.g. leakage current, gain) show little variation that can be traced to substrate choice. Films generally provide less than 100 pA/mm2 leakage current as they show saturation in gain (at approximate fields of 1 V/μm). We recently modified our readout electronics to accept positive bias. Using positive bias on the top electrode provides better charge collection for the lower mobility electrons and (despite process variability) better quality films can provide sensitivities greater than 6 μC/R*cm2, with only partial x-ray absorption, and show less than 20 pA/mm2 dark current.

Paper Details

Date Published: 6 May 2004
PDF: 9 pages
Proc. SPIE 5368, Medical Imaging 2004: Physics of Medical Imaging, (6 May 2004); doi: 10.1117/12.535994
Show Author Affiliations
George Zentai, Varian Medical Systems, Inc. (United States)
Larry Partain, Varian Medical Systems, Inc. (United States)
Raisa Pavlyuchkova, Varian Medical Systems, Inc. (United States)
Cesar Proano, Varian Medical Systems, Inc. (United States)
Gary F. Virshup, Varian Medical Systems, Inc. (United States)
Paul Bennett, Radiation Monitoring Devices, Inc. (United States)
Kanai Shah, Radiation Monitoring Devices, Inc. (United States)
Yuri Dmitriev, Radiation Monitoring Devices, Inc. (United States)
Jerry Thomas, Uniformed Services Univ. of the Health Sciences (United States)


Published in SPIE Proceedings Vol. 5368:
Medical Imaging 2004: Physics of Medical Imaging
Martin J. Yaffe; Michael J. Flynn, Editor(s)

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