退火温度对CsI(Tl)薄膜微观结构和闪烁性能的影响

采用真空热蒸发法制备了CsI(Tl)薄膜, 然后进行了不同温度的真空热处理．用X射线衍射仪、扫描电子显微镜、X射线荧光光谱仪及正电子寿命谱仪对CsI(Tl)薄膜样品进行了分析, 并测得了样品的光产额．结果表明, 该CsI(Tl)薄膜沿(200)晶面择优取向生长．经过较低温度退火, CsI薄膜中的Tl⁺离子向薄膜表面扩散, 薄膜中缺陷数量增加, 且尺寸较大, 光产额略微增高．经过250℃退火, 薄膜中低温退火所形成缺陷得到恢复, 薄膜缺陷尺寸变小, 且数目减少, 具有较好的结晶状态, 光产额提高．经过400℃退火, 薄膜结构发生显著变化, 薄膜中缺陷大幅增加, 结晶状态变差, Ti+含量减少, 光产额急剧下降．

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℃, 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℃ have a good crystalline state and scintillation properties. As the annealing temperature increases to 400℃, the light output of the samples decreases seriously due to the dramatic change of their microstructure and the decrease of Ti⁺.