Tungsten-doped vanadium dioxide thin films on borosilicate glass for smart window application

Abstract

Tungsten-doped VO2 (W–VO2) thin films with low metal–semiconductor transition temperature (Tt) of 34°C were grown on borosilicate glass substrates by reactive ion beam sputtering at room-temperature (RT) followed by a post annealing process. In order to investigate the thermal process effect, four samples S1–S4 were annealed at different temperatures of 490, 530, 570 and 610°C, respectively. X-ray photoelectron spectroscope and Raman measurements demonstrate that the tungsten atoms have been successfully doped into VO2 films. Unlike VO2 thin films which should be annealed at critical temperature, well crystallized W–VO2 films can be annealed in a wide temperature range, i.e. 530–570°C, as revealed by both electrical and optical property investigations. Besides, the infrared (IR) transmittance measured below/above Tt illustrates that W–VO2 films possess excellent switching efficiency, i.e. 33% at 2500nm for S3. Above all, the near RT phase transition, RT deposition, easy control of annealing process and high IR switching efficiency make the W–VO2 thin film a promising material for application of smart windows.