热蒸发紫外LaF3薄膜光学性能和结构表征

在不同的沉积温度下,用热蒸发方法在熔融石英(JGS1)上制备了LaF3单层薄膜。分别采用分光光度计测量了薄膜样品的透射率和反射率光谱,反演得出薄膜的折射率和消光系数;采用原子力显微镜(AFM)观察了样品的表面形貌,并通过表面粗糙度计算得出总积分散射损耗;采用X射线衍射仪(XRD)测试了薄膜的晶体结构,由衍射谱图拟合得到衍射峰的半峰全宽,进而计算出薄膜晶粒的平均尺寸。实验结果表明,随着沉积温度的升高,LaF3薄膜的结晶状况明显变好,晶粒尺寸逐渐变大,膜层变得更加致密,薄膜的光学常数和折射率不均匀性均呈线性变化。沉积温度的增加对薄膜表面粗糙度的影响不明显,散射损耗在光学损耗中所占比例较小,所以光学损耗的变化主要由吸收损耗引起。

Optical Characterization and Structure Properties of Ultraviolet LaF3 Thin Films by Thermal Evaporation

LaF3 single layers are prepared by thermal evaporation at different deposition temperatures on JGS1. Refractive index and extinction coefficient are obtained from the measured transmittance and reflectance spectral curve. Atomic force microscopy (AFM) is used to measure the surface morphology and roughness. The crystal structures and grain size of the thin films are evaluated by X-ray diffraction (XRD). It is found that the crystallization status becomes more compact and the refractive index increases with the deposited temperature. The optical constants and refractive index inhomogeneity of the thin films present linearity. The increasing total optical loss with deposited temperature is attributed to the absorption because the scattering occupies a very low percent in the whole loss.