The optical properties of YF3 films

Abstract The optical, structural and chemical properties of yttrium fluoride films were investigated. Refractive index values of 1.53, 1.48 and 1.3 were found at λ = 0.6 μ m, 4 μ m and 10 μ m respectively for films evaporated onto hot substrates (280 °C). Films evaporated onto substrates at room temperature showed slightly lower refractive indices and strong absorption bands at the water vibrational frequencies ( i.e. at 2.98 μm and 6.5–7.5 μm). The material condensed in amorphous form onto substrates at temperatures below 180 °C, whereas at temperatures above 200 °C all the films showed a crystalline structure. A deposition rate of 0.7 nm s -1 resulted in mechanically stronger films compared with those evaporated at a rate of 1.5 nm s -1 .