Effect of varying the vanadium thickness layer of V2O5/V/V2O5 film on its microstructural and thermochromic properties

• Published in: Journal of vacuum science & technology. A, Vacuum, surfaces, and films Vacuum, surfaces, and films, 2019-09, Vol.37 (5)
• Main Authors: Khanyile, Bhekumuzi Sfundo, Mtshali, Christopher, Madiba, Itani Given, Simo, Aline, Numan, Nagla, Kaviyarasu, Kasinathan, Matinise, Nolubabalo, Nkosi, Mlungisi, Moloi, Sabata Jonas, Maaza, Malik
• Format: Article
• Language: English
• ISSN: 0734-2101; 1520-8559
• DOI: 10.1116/1.5096249

In this study, V2O5/V/V2O5 sandwich-structured films were deposited on glass substrates by electron beam evaporation. The thickness of the first (bottom) V2O5 layer was 40 nm and the last (top) layer was 20 nm, while that of the sandwiched vanadium layer varied up to 12 nm for different samples. The effects of varying the thickness of the sandwiched vanadium layer on microstructural and thermochromic properties of the as-deposited and thermal annealed films were investigated. Ultrahigh-resolution scanning electron microscopy revealed the presence of nanostructures with various irregular shapes on the surfaces of all films. Also, the atomic force microscopy revealed an average roughness of ∼10–38 nm for increasing thickness of the sandwiched vanadium layer. X-ray powder diffraction measurements showed the presence of the monoclinic VO2 (M) crystal structure of the films with (011) preferred orientation at 27.94° for both 7 and 12 nm thicknesses of the sandwiched vanadium layers. The varying thickness of the sandwiched vanadium layers enhanced phase transition temperature values to ∼33.92 and ∼29.11 °C for both 7 and 12 nm thicknesses of the sandwiched layers, respectively. These enhanced transition temperature values, as a result of thickness variation of the sandwiched vanadium layers, pointed toward utilization of this method in the successful synthesis of VO2 films for thermochromic windows application and optoelectronics.