Plasma-Enhanced Atomic Layer Deposition of TiAlN: Compositional and Optoelectronic Tunability

Titanium nitride (TiN) is a unique refractory plasmonic material, the nanocomposites and alloys of which provide further opportunities to tailor its optical and photonic properties. We prepare TiAlN films of continuously variable compositions through the systematic variation of TiN versus AlN cycle ratio in plasma-enhanced atomic layer deposition (PEALD) and investigate the resulting thin-film composition, crystallinity, and optical properties. The resulting properties of TiAlN films are not simple linear combinations of the TiN and AlN films, which exhibit distinct metallic and dielectric properties, but instead are dramatically influenced by the local chemical environment of neighboring constituents. In situ spectroscopic ellipsometry further enables measurement of the varying optical properties of TiAlN films, which evolve over 10 s of nm of film thickness. The tunable optoelectronic properties of TiAlN films enable durable coatings of variable electrical resistance as well as high-temperature diffusion barriers and optical coatings with application to selective solar absorbers and emitters.