Post-annealing microstructural evolution of titanium dioxide thin films grown by thermal and plasma-enhanced atomic layer deposition

Abstract

Titanium dioxide (TiO2) thin films were synthesized by thermal and plasma-enhanced atomic layer deposition (TALD and PEALD) with varying thicknesses and subsequently annealed within the temperature range of 400–1000 °C. It was established that in both cases an increase in the post-annealing temperature led to an improvement in the crystallinity of the TiO2 films and an increase in surface roughness. In the case of the annealing of TiO2 films, deposited by the PEALD method, at temperatures above 800 °C, an increase in the as-deposited layer’s thickness resulted in an increase in the proportion of the rutile phase. The single rutile phase was obtained at a post-annealing temperature of 1000 °C for titanium dioxide films synthesized by the PEALD with 1500 and 2000 cycles. In the case of the annealing of TiO2 films, which were grown by the TALD method, at an annealing temperature of 1000 °C, the formation of coatings with an extremely low proportion of rutile was exhibited. It is concluded from the results obtained that the possibility of structure recrystallization and rutile phase formation was influenced not only by the post-annealing temperature, but also by the thickness and microstructure of the initially synthesized layers.