潮湿空气对碘化铯薄膜结构和性质的影响

采用热蒸发法在普通载玻片上制备了碘化铯(CsI)多晶薄膜,采用扫描电子显微镜(SEM)、X射线衍射仪(XRD)、高阻仪、红外分光光度计研究了暴露于潮湿空气对CsI薄膜结构、电阻率及红外透过率的影响.SEM结果表明,薄膜中颗粒平均尺寸由0.36μm变为1.25μm.吸附水沿颗粒间界扩散,间界发生弯曲和移动,大颗粒吸收小颗粒质量长大.XRD分析表明,(110)晶面衍射峰强度增加,峰位向高角度移动,半高宽减少,薄膜张应力减小,趋于形成(110/220)织构,晶粒平均尺寸为25.6,28.4,45.1 nm.受潮后薄膜电阻率由1010?·cm量级减少为108?·cm量级.在3675—3750 cm-1和3560—3640 cm-1位置出现接近游离水而非液态水的红外吸收峰,观察到吸收峰的精细结构,峰分裂源于受离子偶极键影响的羟基与吸附水气液界面处悬键的伸缩振动.

Influence of air exposure on the structure and properties of cesium iodide film

Polycrystalline cesium iodide (CsI) thin films were prepared on glass substrates by thermal evaporation. The Influences of air exposure on the structure, resistivity and infrared transmittance of CsI film were investigated by scanning electron microscopy, X-ray diffraction (XRD), high resistance meter and infrared spectrophotometer (IR). It is found that the coalescence of grains occurs and the average grain size increases from 0.36 μm to 1.25 μm. The mechanism of grain growth is attributed to the diffusion of water molecules along grain boundaries and the migration of grain boundaries driven by minimization of total free energy. XRD results indicate the formation of (110/220) texture when exposed to ambient air and the relaxation of tensile stress during recrystallization. The average crystallite sizes obtained from Debye-Scherrer's formula are 25.6 nm, 28.4 nm and 45.1 nm respectively. The resistivity of the film decreases from the order of 10¹⁰ Ω·cm to 10⁸ Ω· cm. The IR absorption bands in the ranges of 3675-3750 cm^-1 and 3560-3640 cm^-1 closely resemble that of free water rather than liquid water. The observed split bands are assigned to the non-hydrogen-bonded OH associated with ion-dipole bonds and dangling OH at air-water interface respectively.
Keywords： CsI films grain boundary diffusion structural analysis IR vibration