热蒸发与离子束溅射制备LaF 3 薄膜的光学特性

Abstract

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 LaF3 thin films were measured by an UV-visible spectrophotometer,and the refractive indexes and extinction coefficients were obtained by using different models. Second,stresstemperature curves of LaF3 thin films during heating and cooling cycles were carried out by a stress measurement system. Finally,the X-ray diffraction( XRD) was used to characterize the microstructure of LaF3 layers.Experimental results indicate that LaF3 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- 4for RH LaF3,and 1. 714 and 9 ×10- 4for IBS LaF3,respectively. RH LaF3 and IBS LaF3 exhibited inverse stress status. RH LaF3 had a tensile stress and IBS LaF3 showed a compressive stress,which decreased after annealing. 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.