Alkali metal halides are white powders at room temperature, with an evaporation temperature of 1180 ℃ under 10-2Pa vacuum. They can be evaporated using nickel, molybdenum, tantalum, tungsten boats, or Al2O3 crucibles. Electron beam heating has a better evaporation effect. LiF has high transparency in the ultraviolet region, with a transparent range of 110nm~7 μ m and a refractive index value of 1.36-1.37 at 550nm. The refractive index value of LiF thin film varies over time and exhibits non-uniformity with increasing film thickness. The mechanical properties of LiF film are poor and it has hygroscopicity.