VAPOR-DEPOSITED CAWO4 PHOSPHOR

In this paper we describe the preparation, microstructure, and x-ray e xcited luminescence of vapor-deposited CaWO4 films up to about 50 mu m thick, comparing them to particulate CaWO4 phosphor screens, used in medical diagnostic imaging. Films that we e-beam evaporated on substra tes heated at or above 500 degrees C were polycrystalline with the sch eelite structure, while on unheated substrates, films were initially a morphous but became crystalline after annealing them in air above abou t 750 degrees C. Crystalline CaWO4 films irradiated with x-rays produc ed light emission peaked at 430 nm. The emission intensity depended on film thickness and grain size and was comparable to particulate CaWO4 phosphor screens. Because the vapor-deposited films also exhibited su perior resolution, they are promising for diagnostic x-ray imaging.