OPTICAL-PROPERTIES OF REACTIVELY SPUTTERED GEO2 IN THE VACUUM-ULTRAVIOLET REGION

Optical properties of sputtered GeO2 films submitted to various heat t reatments are investigated with measurements in the vacuum ultraviolet region by means of the multi-angle reflectivity method. A Kramers-Kro nig analysis of the near-normal-incidence reflectivity is compared wit h previous results on glassy and polycrystalline GeO2. The films were sputtered from a germanium target (99.999%) in an argon + oxygen mixtu re 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 reflecti on measurements and used for the Penn gap model calculations. Using th e density correlation in the f-sum rule, the Penn gap energies for hex agonal and glassy GeO2 have been obtained and are compared with the av erage interband transition energy in GeO2 spectra.