Preparation and Infrared Optical Properties of W-V Co-sputtered Thermochromic Thin Films

Abstract:

Tungsten-vanadium (W-V) co-sputtered thermochromic thin films of low-cost were designed in order to solve the problems of pure vanadium dioxide (VO2) thin films including high phase transition temperature, broad width of thermal hysteresis loop and low infrared transmittance after being doped. The metal thin films of 1.4% tungsten concentration were prepared on the glass substrates by magnetron co-sputtering at room temperature, and then the prepared metal thin films were sufficiently oxidized to the thermochromic thin films by annealing under the air condition. The structure and morphology of the samples collected from the prepared thin films were analyzed by XPS, XRD and SEM, which shows that W-V co-sputtering approach does not modify the preferred orientation growth of VO2 thin films on glass substrates, but significantly changes the surface morphologies of VO2 thin films. The optical properties of W-V co-sputtered thin films were compared with that of VO2 thin films by spectrophotometer, and the phase transition temperature drops from 68 oC to 40 oC, the width of thermal hysteresis loop narrows from 6 oC to 3 oC, and the infrared transmittances at low temperature are 62% and 57%, respectively. Results demonstrate W-V co-sputtering approach can reduce the phase transition temperature, limit the thermal hysteresis loop and gently change the infrared transmittance.