Atomic Layer Deposition and Thermal Transformations of Thin Titanium–Vanadium Oxide Films

Abstract

Titanium–vanadium oxide (TixVyOz) nanofilms were prepared by atomic layer deposition using TiCl4, VOCl3, and water. The film growth was monitored in situ by quartz crystal microbalance. At a deposition temperature of 115°С, the films grew linearly with number of deposition cycles, and the surface reactions of the precursors were self-limiting. Films of two compositions, Ti0.9V0.1O3 and Ti0.5V0.5O3, were prepared; their density was 3.5 and 3.3 g cm–3, respectively. The content of Cl impurities in the films obtained was less than 0.2 at. %, the coating roughness was ~4.0 Å, and the band gap was 3.05 and 2.85 eV for Ti0.9V0.1O3 and Ti0.5V0.5O3, respectively. All the films obtained were amorphous. The heat treatment of the Ti0.5V0.5O3 film in air led to the formation of heterostructural TiO2–V2O5 coatings. At 450°С, nanostructures consisting of anatase TiO2 and nanorods of microcrystalline V2O5 were formed. An increase in the annealing temperature to 500°С led to increase in the length of V2O5 nanowires to tens of micrometers and to their separation from the substrate, and after annealing at 550°С the substrate surface was uniformly coated with nanoparticles. The films obtained in this study can find use in the development of catalysts and power storage systems.