형광체 기반 X선 광 변조기를 위한 비정질 셀레늄 필름 특성

Abstract

PXLM(Phosphor based x-ray light modulator) has a combined structure by phosphor, photoconductor, and liquid crystal and it can realize x-ray image of high resolution in clinical diagnosis area. In this study, we fabricated a photoconductor and investigated electrical and optical properties to confirm application possibility of radiator detector of PXLM structure. As photoconductor, amorphous selenium(a-Se), which is used most in DR(Digital radiography) of direct conversion method, was used and for formation of thin film, it was formed as 20㎛-thick by using thermal vacuum evaporation system. For a produced a-Se film, through XRD(X-ray diffraction) and SEM(Scanning electron microscope), we investigated that amorphous structure was uniformly established and through optical measurement, for visible light of 400～630㎚, it had absorption efficiency of 95 % and more. After fabricated a-Se film on the top of ITP substrate, hybrid structure was manufactured through forming Gd2O3:Eu phosphor of 270㎛-thick on the bottom of the substrate. As the result to confirm electrical property of the manufactured hybrid structure, in the case of appling 10 V/㎛, leakage current of 2.5nA/㎠ and x-ray sensitivity of 7.31nC/㎠/mR were investigated. Finally, we manufactured PXLM structure combined with hybrid structure and liquid crystal cell of TN(Twisted nematic) mode and then, investigated T-V(Transmission vs. voltage) curve of external light source for induced x-ray energy. PXLM structure showed a similar optical response with T-V curve that common TN mode liquid crystal cell showed according to electric field increase and in appling 50～100V, it showed linear transmission efficiency of 12～18%. This result suggested an application possibility of PXLM structure as radiation detector.