Fabrication and Characterization of Multi-layer Heat Mirror with Photocatalytic Properties

A novel TiO2(5)/TiO2(buffer)/Ti(4)/Ag(3)/Ti(2)/TiO2(1) multi-layer film coating with corning glass is designed and fabricated by a dc magnetron sputtering method as a renovation of the well-known TiO2/Ti/Ag/Ti/TiO2 system in order to obtain a heat mirror system with photocatalytic properties due to sufficient thickness of the TiO2 layer. The outer TiO2 layer is fabricated in two steps, possibly claimed as two layers TiO2(5) and TiO2(buffer), among which the 70-nm-thick layer TiO2(buffer) deposited in poor oxygen effectively minimizes the oxidation toward its neighbor Ti(4) layer. The optimal total thickness of the TiO2(5) and TiO2(buffer) di-layer is found to be 300 nm to yield a highly photo-catalytic property of the film without affecting the optical properties considerably. This multi-layer film can transmit light of above 75–85% in the visible spectrum (380 ≤ λ ≤ 760 nm) and reflect radiation of above 90% in the infrared spectrum (λ ≥ 760 nm). Such multi-layer coatings are strongly recommended not only as promising transparent heat mirrors but also as photo-catalytic films for architectural window coatings.