Temperature-Dependent Properties of Atomic Layer Deposition-Grown TiO2 Thin Films

This study investigates the presence of titanium oxynitride bonds in titanium dioxide (TiO2) thin films grown by atomic layer deposition (ALD) using tetrakis dimethyl amino titanium (TDMAT) and water at temperatures between 150 and 350 degrees C and its effect on the films' optical and electrical properties. Compositional analysis using X-ray photoelectron spectroscopy (XPS) reveals increased incorporation of oxynitride bonds as the process temperature increases. Furthermore, depth profile data demonstrates an increase in the abundance of this type of bonding from the surface to the bulk of the films. Ultraviolet-visible spectroscopy (UV-vis) measurements correlate increased visible light absorption for the films with elevated oxynitride incorporation. The optical constants (n, k) of the films show a pronounced dependence on the process temperature that is mirrored in the film conductivity. The detection of oxynitride bonding suggests a secondary reaction pathway in this well-established ALD process chemistry, that may impact film properties. These findings indicate that the choice of process chemistry and conditions can be used to optimize film properties for optoelectronic applications.