Chloride atomic-layer chemical vapor deposition of TiO₂ with a chloride pretreatment of substrates

Abstract
A procedure for changing the course of the atomic-layer chemical vapor deposition (ALCVD) growth of TiO₂ from TiCl₄ and H₂O on amorphous SiO₂ substrates/underlayers at low temperatures is proposed. The changes are characterized by the real-time incremental dielectric reflection measurements and post-growth spectrophotometry and reflection high-energy electron diffraction measurements. In the procedure, an ultrathin layer of the material is deposited and, subsequently, in situ inhomogeneously etched in the TiCl₄ flow, both steps being performed at a temperature above 350°C. As a result, an ultrathin microrough mixed amorphous/anatase-phase surface layer is created. By using this layer as a seed layer, the crystalline-growth temperature of the material is reduced. So anatase (mixed with amorphous phase) TiO₂ thin films on SiO₂ substrates at 125°C are, for the first time, grown. The films are shown to be depth-inhomogeneous. The upper part of the films, when they are thicker, is well textured