Vapor-deposited CaWO 4 phosphor

In this paper we describe the preparation, microstructure, and x-ray excited luminescence of vapor-deposited CaWO{sub 4} films up to about 50 {mu}m thick, comparing them to particulate CaWO{sub 4} phosphor screens, used in medical diagnostic imaging. Films that we e-beam evaporated on substrates heated at or above 500{degree}C were polycrystalline with the scheelite structure, while on unheated substrates, films were initially amorphous but became crystalline after annealing them in air above about 750{degree}C. Crystalline CaWO{sub 4} films irradiated with x-rays produced light emission peaked at 430 nm. The emission intensity depended on film thickness and grain size and was comparable to particulate CaWO{sub 4} phosphor screens. Because the vapor-deposited films also exhibited superior resolution, they are promising for diagnostic x-ray imaging. {copyright} {ital 1997 Materials Research Society.}