Compositional correlation and polymorphism in BaF2-PrF3 thin films deposited using electron-beam evaporation

作     者：He, Weixiang Zheng, Weimin Xie, Ping Li, Bin Lv, Xuwen Jing, Chao Liu, Dingquan 

作者机构：Shanghai Univ Dept Phys Shanghai 200444 Peoples R China Shandong Univ Sch Space Sci & Phys Weihai 264209 Peoples R China Chinese Acad Sci Shanghai Inst Tech Phys Shanghai 200083 Peoples R China Shanghai Tech Univ Sch Phys Sci & Technol Shanghai 200031 Peoples R China 

出 版 物：《THIN SOLID FILMS》 (固体薄膜)

年 卷 期：2019年第669卷

页      面：558-563页

核心收录：

学科分类：08[工学] 0805[工学-材料科学与工程（可授工学、理学学位）] 0702[理学-物理学] 

基　　金：National Science Foundation of China (NSFC) [61675223, 51371111] Shandong Province Natural Science Foundation, China [ZR2017MF018] Innovation Program in Shanghai Institute of Technical Physics, CAS [CX-173] 

主　　题：Infrared low -index evaporation materials BaF2-PrF3 Electron beam evaporation Compositional correlation Polymorphism 

摘      要：Infrared low-index evaporation materials are essential in the broadband antireflection coatings to reduce Fresnel reflections on the surfaces of infrared optical components. Although the layers of praseodymium fluoride (PrF3) show an excellent transparency and the lower refractive index n and extinction coefficient k in the spectral range of thermal infrared, the tensile stress presented in the layers prohibits PrF3 from being used as infrared low-index coating materials. A practical solution to reduce stress is to directly evaporate the admixture of PrF3 with alkaline fluorides, such as barium fluoride (BaF2). However, due to the significant difference of vapor pressures between PrF3 and BaF2, it is commonly difficult to congruently deposit PrF3-BaF2 thin films utilizing evaporating directly from a single source. Moreover, more details are unknown about the phase compositions of PrF3-BaF2 thin films. In our investigation, BaF2-PrF3 thin films were deposited using electron beam evaporation from the sintered ingots of PrF3 admixed with BaF2. The compositions of thin films were characterized using energy dispersive X-ray spectroscopy (EDX), the crystallographic structures were explored by X-ray-diffraction (XRD). It was revealed that the concentration of BaF2 in thin films can be correlated to that in the admixtures. Moreover, in addition to PrF3 and BaF2, the phase compositions in thin films include also secondary phases, such as PrOF, PrF4, Pr2F2, BaPrF6, and that of elemental Ba.