Preparation of amorphous fluoride films by electron cyclotron resonance plasma-enhanced chemical vapor deposition

Abstract

Amorphous ZnF 2, ZnF 2–BaF 2, AlF 3 and AlF 3–BaF 2 films were prepared on CaF 2(1 1 1) substrates by an electron cyclotron resonance plasma-enhanced chemical vapor deposition (CVD) technique. Metal β-diketone chelates and NF 3 gas were used as starting materials and a fluorinating gas, respectively. ZnF 2 films deposited on the substrates kept at 300°C and 100°C were crystalline and amorphous, respectively. The crystalline ZnF 2 thin film prepared at a deposition rate of 0.2 μm h −1 was oriented along a [1 1 0] direction. The amorphous ZnF 2 film, tinted yellowish brown, had an IR spectra which were due to contaminants. Colorless and contaminant-free amorphous films were obtained for a 60ZnF 2·40BaF 2 composition. On the other hand, AlF 3 films generated on the CaF 2(1 1 1) substrate kept at 300°C were amorphous and colorless. We also found that amorphous 80AlF 3·20BaF 2 and 60AlF 3·40BaF 2 films could be synthesized at a deposition rate of 1.5 μm h −1 .