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 300nm 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 ≤760nm) and reflect radiation of above 90% in the infrared spectrum (λ≥760nm). Such multi-layer coatings are strongly recommended not only as promising transparent heat mirrors but also as photo-catalytic films for architectural window coatings.