Optical properties of reactively sputtered GeO2 in the vacuum ultraviolet region

Abstract Optical properties of sputtered GeO 2 films submitted to various heat treatments are investigated with measurements in the vacuum ultraviolet region by means of the multi-angle reflectivity method. A Kramers-Kronig analysis of the near-normal-incidence reflectivity is compared with previous results on glassy and polycrystalline GeO 2 . The films were sputtered from a germanium target (99.999%) in an argon + oxygen mixture at a total pressure of 0.6 Pa and oxygen pressure of 0.24 Pa, with a target power density of 1.6 W/cm 2 . The deposition rate was about 1.5 nm/min. The film density has been evaluated by X-ray total reflection measurements and used for the Penn gap model calculations. Using the density correlation in the f -sum rule, the Penn gap energies for hexagonal and glassy GeO 2 have been obtained and are compared with the average interband transition energy in GeO 2 spectra.