PECVD of amorphous TiO2 thin films: effect of growth temperature and plasma gas composition

Amorphous TiO2 thin films are grown using a r.f. plasma-enhanced chemical vapour deposition process at substrate temperatures between 393 and 523 K using titanium tetraisopropoxide as a precursor, and Ar or N2, pure or mixed with O2, as the plasma gas. All films are smooth and adherent, their roughness slightly increases by increasing the substrate temperature or if oxygen is added to the plasma gas. Films grown in the presence of oxygen result transparent in the visible region and highly resistive, as expected for pure titanium dioxide. Films grown in an oxygen-free plasma appear grey-blue and fairly conductive suggesting the presence of Ti(III) species. The operating conditions provide high deposition rates, up to 37 nm/min in the presence of oxygen.