MODIFICATION OF OPTICAL AND MECHANICAL-PROPERTIES OF BAF2 BOMBARDED BY EITHER XE OR AR ION

Barium fluoride (BaF2) material presents a low absorption in a wide range of the spectrum (0.25-15-mu-m) and a low value of refractive index as well. Typical evaporated thin film of barium fluoride is hygroscopic and presents a low packing density value. The ion assistance by low energy ion beam has been used to improve the mechanical stability and to increase the packing density of evaporated thin films. In this work the BaF2 coatings have been ion bombarded by either Ar ions or Xe ions during the evaporation. The ion beam energy was varied in the range from 300 to 800 eV. The refractive index and the Knoop hardness values of the Xe bombarded samples are higher than the Ar bombarded ones. Besides, the Xe assisted samples present exact stoichiometric values (measured by Rutherford backscattering technique) and their absorption coefficient values (in the UV-VIS region) are lower than those of the Ar assisted samples.