退火温度对CsI(T1)薄膜微观结构和闪烁性能的影响

Effect of Annealing Temperature on the Microstructure and Scintillation Properties of CsI(T1) Films

采用真空热蒸发法制备了CsI(T1)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(T1)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(T1)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T1^+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.

CsI（T1） 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 atter anneaiea. 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^＋.