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Zinc Sulfide selenium X-ray Detector for Digital Reaiography
ji-KoonPark,Sang-SikKang,Jae-HyungKim,Chi-WoongMun,Sang-HeeNam 한국전기전자재료학회 2002 Transactions on Electrical and Electronic Material Vol.3 No.4
The high bias voltage associated with the thick layer (typically 500-1000 ㎛) of selenium required to have an acceptable x-ray absorption in radiography and fluoroscopy applications may have some practical inconvenience. A hybrid x-ray detector with zinc sulfide-amorphous selenium structure has been developed to improve the x-ray sensitivity of a a-Se based flat-panel digital imaging detector. Photoluminescence(PL) characteristic of a ZnS:Ag phosphor layer showed a light emission peak centered at about 450 nm, which matches the sensitivity spectrum of selenium. The dark current of the hybrid detector showed similar characteristics with that of a a-Se detector. The x-ray sensitivity of hybrid and a-Se x-ray detector was 345 pC/cm2/mR and 295 pC/cm2/mR at an applied voltage of 10 V/㎛, respectively. The purpose of this study was to evaluate the pertinence of a solution using a thin selenium layer, as a photosensitive converter, with a thick coating of silver doped zinc sulfide phosphor.
Study on Electrical Properties of X-ray Sensor Based on ScI:Na-Selenium Film
Ji-KoonPark,Sang-SikKang,Dong-GilLee,Jang-YongChoi,Jae-HyungKim,Sang-HeeNam 한국전기전자재료학회 2003 Transactions on Electrical and Electronic Material Vol.4 No.3
In this paper, we have introduced the x-ray detector built with a CsI:Na scintillation layer deposited on amorphous selenium. To determine the thickness of the CsI:Na layer, we have estimated the transmission spectra and the absorption of continuous x-rays in diagnostic range by using computer simulation (MCNP 4C). A x-ray detector with 65㎛-CsI:Na/30㎛-Se layer has been fabricated by a thermal evaporation technique. SEM and PL measurements have been performed. The dark current and x-ray sensitivity of the fabricated detector has been compared with that of the conventional a-Se detector with 100 ㎛ thickness. Experimental results show that both detectors exhibit a similar dark current, which was of a low value below 400 pA/cm2 at 10 V/㎛. However, the CsI:Na-Se detector indicates high x-ray sensitivity, roughly 1.3 times that of a conventional a-Se detector. Furthermore, a CsI:Na-Se detector with an aluminium reflective layer shows a 1.8 times higher x-ray sensitivity than an a-Se detector. The hybrid type detector proposed in this work exhibits a low dark current and high x-ray sensitivity, and, in particular, excellent linearity to the x-ray exposure dose.