Vanadium dioxide thermochromic thin films correlation between microstructure, electrical and optical properties
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Date
2008
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Abstract
Thermochromic thin films of vanadium dioxide (VO2) were successfully prepared using two physical vapour deposition methods namely Pulsed Laser Deposition (PLD) and Inverted Cylindrical Magnetron Sputtering (ICMS). We used these two techniques in order to comparatively study the effect of deposition temperature on VO2 thin films microstructure, electrical and optical properties. Prior to the deposition, we first optimized the deposition conditions for both techniques. Optimized conditions were then used to systematically study the effect of substrate temperature, ranging from 350oC to 550oC, on the microstructure and the switching properties of VO2 thermochromic thin films. All films prepared by PLD were observed to be crystallized, giving a first peak at 27.87o corresponding to (011) plane indicating the existence of VO2 [5,9,13,18,21]. We also observed (by Debye Shrerer’s formula) that the film grain size increases with the increase in substrate temperature. AFM was employed so as to study the surface roughness. We observed the electrical and optical properties for VO2 behaviour using four point probe and UV-VIS spectrophotometer.
The same procedure used for characterizing VO2 thin film synthesized by PLD was also repeated for ICMS results. The films deposited by ICMS were also found to be crystallized, showing strong texturation corresponding to (011) plane indicating VO2 existence [5,12,13,18,21]. We observed that optical and electrical properties exhibited by VO2 thin films are almost the same with substrate temperature increase. ICMS technique appears to be a better technique to as compared to PLD to synthesize or deposit high quality films which would show clear substrate temperature dependence as it appears to be important effect in the study.
Description
Thesis presented in fulfilment of the requirements for the degree of Master of Sciences at the University of Zululand, 2008.
Keywords
Thermochromic