Growth of CsI(Tl) scintillation film

Abstract

CsI(Tl) is widely used as scintillation material for the high energy particles and ionizing radiation detectors. In the last decade imaging devices with high spatial resolution based on CsI(Tl) thin layers were developed due to the ability of CsI(Tl) film to grow in columnar morphology. This reduces the lateral light spread and promotes the directional light passing due to the total internal reflection on column boundaries. CsI(Tl) films of 5-200 μm thickness were obtained by physical vapour deposition technique onto the (100) cleavage planes of LiF single crystal used as orienting substrate and onto the amorphous glass substrates. In both cases columnarmorphology of films was observed. Vacuum deposition of CsI(Tl) onto the orienting LiF substrate at appropriate conditions leads to columnar morphology of the grown layer and single crystalline structure of blocks in two orientations, (110) and (112) (the halfwidth of rocking curves was from 8 to 20 arc min for (110) orientation and from 5 to 23 arc min for (112)), that are not coincident with (100) orientation of substrate. This may be the result of great lattice misfit and weak counteraction between the layer and substrate that provides theVolmer-Weber condensationmode and epitaxial growth according to coincident nodes mechanism. Columnar CsI(Tl) films demonstrate increased scintillation efficiency comparing with the standard CsI(Tl) single crystalline α detector at thicknesses more than 10 mkm. m10.p05