Effect of Annealing Temperature on the Microstructure and Scintillation Properties of CsI(Tl) Films

CsI(Tl) films were prepared by thermal evaporation and annealed at various temperatures. Structure and scintillation properties of the films were examined using X-ray diffraction, scanning electron microscope, X-ray fluorescence spectrometry, positron annihilation lifetime spectroscope and scintillation pulse height spectrometry. Results show that the CsI films are in micro-columnar structure with a preferential (200) orientation. When the sample is annealed at 150 degrees C, Tl+ ions diffuse to the sample surface. Consequently, the amount and size of the vacancy type of defects increase. However,the light yield increases a little after annealed. The samples annealed at 250 degrees C have a good crystalline state and scintillation properties. As the annealing temperature increases to 400 degrees C, the light output of the samples decreases seriously due to the dramatic change of their microstructure and the decrease of Ti+.