热蒸发与离子束溅射制备LaF3薄膜的光学特性

研究了钼舟热蒸发工艺和离子束溅射方法制备的单层LaF₃薄膜的特性。首先，采用分光光度计测量了LaF₃薄膜的透射率和反射率光谱，使用不同模型拟合得出薄膜的折射率和消光系数。然后，采用应力仪测量了加热和降温过程中LaF₃薄膜的应力-温度曲线。最后，采用X射线衍射仪测试了薄膜的晶体结构。实验结果表明，热蒸发制备的LaF₃（RH LaF₃）存在折射率的不均匀性，在193 nm，其折射率和消光系数分别为1.687和5×10^-4，而离子束溅射制备的LaF₃（IBS LaF₃）折射率和消光系数分别为1.714和9×10^-4。两种薄膜表现出相反的应力状态，RH LaF₃薄膜具有张应力，而IBS LaF₃具有压应力，退火之后其压应力减小。热蒸发制备的MgF₂/LaF₃减反膜在193 nm透过率为99.4%，反射率为0.04%，离子束溅射制备的AlF₃/LaF₃减反膜透过率为99.2%，反射率为0.1%。

Optical properties of LaF3 thin films prepared by thermal evaporation and ion beam sputtering

To meet the requirements for different practical applications , we investigate the properties of single LaF3 layer deposited by resistive heating Mo-boat（RH） and ion beam sputtering（IBS） in this paper.First, transmittance and reflectance spectra of LaF 3 thin films were measured by an UV-visible spectrophotometer , and the refractive indexes and extinction coefficients were obtained by using different models .Second , stress-temperature curves of LaF 3 thin films during heating and cooling cycles were carried out by a stress measure-ment system.Finally, the X-ray diffraction（XRD） was used to characterize the microstructure of LaF 3 layers. Experimental results indicate that LaF 3 thin film fabricated by thermal evaporation （ RH LaF3 ） had an inhomo-geneous refractive index;the refractive index and extinction coefficient at 193 nm are 1.687 and 5 ×10 -4 for RH LaF3 , and 1.714 and 9 ×10 -4 for IBS LaF3 , respectively.RH LaF3 and IBS LaF3 exhibited inverse stress status.RH LaF3 had a tensile stress and IBS LaF 3 showed a compressive stress , which decreased after annea-ling.The transmittances are 99.4%and 99.2%for RH deposited MgF2/LaF3 AR coating and IBS deposited AlF3/LaF3 AR coating, and the corresponding measured reflectances are 0.04%and 0.1%,respectively.