Thermochromic properties and low emissivity of ZnO:Al/VO2 double-layered films with a lowered phase transition temperature

We studied the optical and semiconductor-metal (S-M) transition properties of ZnO:Al/VO2/substrate double-layered films that consisted of a ZnO:Al top layer and a VO2 bottom layer. ZnO:Al and VO2 films were grown on fused silica substrates by radio frequency magnetron sputtering and polymer-assisted deposition, respectively. The ZnO:Al/VO2/substrate films displayed low emissivity (0.31-0.32) with integrated luminous transmittance (T-lum > 46%) and thermochromic properties (Delta T-sol > 4.1%). The low emissivity and thermochromic properties were independently introduced by the transparent conductive ZnO:Al layer and the VO2 layer. In addition, the S-M transition temperatures for VO2 shifted to lower temperatures after the ZnO:Al deposition process, which was due to the formation of surface nonstoichiometry-oxygen deficiency that was induced by the ZnO:Al deposition process. (C) 2011 Elsevier B.V. All rights reserved.