Preparation and characterization of vanadium dioxide films.
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Date
1998
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University of Dar es Salaam
Abstract
Vanadium dioxide films were prepared by do and rf reactive magnetron sputtering of vanadium target, 99.7% purity in an Ar + 02 plasma with a controlled oxygen partial pressure. Films were deposited onto normal glass substrates at 400°C. The films have a metal -semiconductor transition at a temperature ic = 65°C - 68°C. Optical and electrical properties of the films were investigated around the metalsemiconductor phase transition. Sheet resistance of the films were recorded using a four point probe over the temperature range 26 £ i £100°C It was observed that the sheet resistance can change by three orders of magnitude when heating the films from room temperature to temperature above the transition. Optical measurements were carried out below and above the transition temperature using substrate heating devices constructed and fixed in the sample compartment of the spectrophotometer. Transmittance of the films were obtained in the 300 £ l £ 2500 nm wavelength range at the two temperatures (i.e. 26 and 100°C). The luminous transmittance was rather unaffected by the temperature above the transition, whereas near infrared transmittance showed lower values about ic. Optical constants, n and k were measured by ellipsometric method for the wavelength, l = 632.8 nm, at an angle of incidence of 70°. The Semiconducting state optical constants were found to be 2.67 and 0.04 for n and k respectively, while the metallic state values were 2.26 for refractive index and 0.3 for the extinction coefficient. Film thicknesses were obtained using Talystep instrument.
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Keywords
Vanadium oxide
Citation
Samiji, M. E. (1998). Preparation and characterization of vanadium dioxide films. Master dissertation, University of Dar es Salaam. Available at (http://41.86.178.3/internetserver3.1.2/search.aspx?formtype=advanced)