Effects of thickness on the structural, electronic, and optical properties of MgF2 thin films: The first-principles study

First-principles calculations were performed on MgF2 (0 0 1) thin films and their structural, electronic, and optical properties were investigated. Results showed that the films are energetically stabilized when the layer number is increased to 25, corresponding to a thickness of about 4 nm. The thin films exhibited narrower band gaps compared with their bulk counterparts; gaps increased with increasing thickness of the thin films. Analysis of the optical properties of the films showed that their refractive index is significantly decreased and their extinction coefficient is slightly increased compared with the bulk. With increasing thin film thickness, the refractive index decreased slightly and the extinction coefficient remained unchanged. These results indicate that MgF2 thin films of a certain thickness range have excellent performance as anti-reflection and high-reflection coatings at visible wavelengths.