6 May 2004 Improved properties of PbI2 x-ray imagers with tighter process control and using positive bias voltage
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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.
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George Zentai, George Zentai, Larry Partain, Larry Partain, Raisa Pavlyuchkova, Raisa Pavlyuchkova, Cesar Proano, Cesar Proano, Gary F. Virshup, Gary F. Virshup, Paul Bennett, Paul Bennett, Kanai Shah, Kanai Shah, Yuri Dmitriev, Yuri Dmitriev, Jerry Thomas, Jerry Thomas, } "Improved properties of PbI2 x-ray imagers with tighter process control and using positive bias voltage", Proc. SPIE 5368, Medical Imaging 2004: Physics of Medical Imaging, (6 May 2004); doi: 10.1117/12.535994; https://doi.org/10.1117/12.535994

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