Dispersion properties of (La0.06Ga0.94)2O3:Eu thin films

Abstract

The dispersion of the refractive index of (La0.06Ga0.94)2O3:Eu thin films obtained by radio-frequency ion-plasma sputtering has been studied. It was found that the films have a polycrystalline structure corresponding to the monoclinic structure of β- Ga2O3. It is shown that the freshly deposited films are characterised by an abnormal dispersion, and after annealing in argon, a normal dispersion of the refractive index is observed. It was found that at normal dispersion, the spectral dependence of the refractive index in the visible region of the spectrum is mainly determined by electronic transitions from the 2p-state oxygen band, which form the upper filled level of the valence band to the bottom of the conduction band formed by hybridised 2p-states of oxygen and 4s-states of gallium. Two single-oscillator approximation models were analysed and compared for the films annealed in argon, and the approximation parameters, dispersion energy, degree of chemical bond ionicity, coordination number, and static refractive index were determined.