Preparation and characterization of amorphous GaF 3 and GaF 3–BaF 2 thin films by ECR microwave plasma-enhanced CVD

Abstract

Amorphous GaF 3 and GaF 3–BaF 2 thin films were prepared by electron cyclotron resonance microwave plasma-enhanced chemical vapor deposition. Metal β-diketonates and a NF 3 gas were used as starting materials and a fluorinating reagent, respectively. Single crystals of CaF 2(1 1 1) were employed as substrates. Almost contaminant-free and amorphous GaF 3 and GaF 3–BaF 2 films were obtained on the substrates kept at 300 °C at the deposition rates of 0.8 μm h −1 and 1.1–1.8 μm h −1, respectively. In amorphous GaF 3–BaF 2 films, optical propagation was detected at one or two transverse electric modes. The refractive indices of GaF 3–BaF 2 thin films increased with the BaF 2 content. Based on the measured refractive indices, moreover, the synthesis condition of single-mode planar optical waveguides were determined. Consequently, the optimum thickness of amorphous GaF 3–BaF 2 thin film was estimated to be approximately 0.3–1.6 μm.