Atomic Layer Deposition of AlF3 Thin Films Using Halide Precursors

Abstract

Aluminum fluoride thin films have potential in both optic and lithium-ion battery applications. AlF3 thin films have mostly been deposited using physical vapor deposition methods. In this study, we present a new atomic layer deposition process for AlF3. Our method makes use of a halide–halide exchange reaction with AlCl3 and TiF4 as the precursors. With this new chemistry, thin films of AlF3 can be deposited at a temperature range of 160–340 °C. The films have been studied by UV–vis spectroscopy, field emission scanning electron microscopy, X-ray diffraction, X-ray reflectance, atomic force microscopy, time-of-flight elastic recoil detection analysis (ToF-ERDA), energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. At 220 °C, the growth rate of the films is approximately 1.1 Å per cycle, and the refractive index is 1.36 (at 580 nm). The films show only small amounts of Cl and Ti impurities when deposited at high temperatures, as determined by ToF-ERDA. Surface oxidation of the films due to moisture in ambient air is observed.