Multi-functional self-cleaning thermochromic films by atmospheric pressure chemical vapour deposition

Thin films of titanium dioxide and vanadium dioxide were deposited onto glass using atmospheric pressure chemical vapour deposition (APCVD). The films were investigated as individual layers and as part of multilayer systems to assess their potential to be combined to offer dual functionality, self-cleaning thermochromic films. The multilayer systems were achieved by deposition of vanadium dioxide with subsequent titanium dioxide deposition and vice-versa. XRD revealed that the titanium dioxide existed exclusively in the anatase form and the vanadium oxide either monoclinic VO2 or mixed vanadium oxides, depending on the position within the multilayer structure. XPS analysis indicated good stoichiometry in the films, and also suggested that the films remained elementally discrete when deposited in the multilayer systems. The multilayered films were active in the destruction of stearic acid layers under UV radiation and showed good thermochronmic switching properties. Furthermore, the titania over-layer imparted a significant degree of enhanced durability to the underlying thermochromic film. This combination of enhanced durability and 'self-cleaning' property, offers interesting potential for wider potential use of this technology. (C) 2007 Elsevier B.V. All rights reserved.