OPTICAL AND THERMAL-PROPERTIES OF ELECTRON-TRAPPING AND HOLE-TRAPPINGSITES IN THE X-RAY STORAGE PHOSPHOR RBL-X (X=TL(+), IN(+), PB(2+), EU(2+)

Two-dimensional x-ray detectors based on x-ray storage phosphors are u tilized in the field of medicine, biology, and physics. Defect centers and mechanisms contributing to the photostimulated luminescence (PSL) process of the x-ray storage phosphor RbI:X (X = Tl+, In+, Pb2+, Eu2) are reported. By optical and thermoluminescence spectroscopy the ele ctron and hole storage centers involved in the PSL process were identi fied. F- and Z type and Tl0 centers turned out to be the occupied elec tron storage centers, V(K-) and dopant-related V(KA) centers the hole- trapping sites. The specific choice of the dopant yields storage phosp hors with different physical properties, such as emission characterist ics, photostimulation characteristics, and thermal stability of the in formation storage. At T = 300 K the information stored in the RbI:Tlphosphor is unstable, in RbI:Eu2+ it is nearly stable and in RbI:In+ s table. A physical model for the PSL as well as for the thermoluminesce nce is derived. In the Tl+-doped material Tl0 centers were found to ac t as efficient electron storage centers at temperatures below 180 K wi th a 4.7 times larger storage capability than F centers.