Substrate temperature effects on the structural, compositional, and electrical properties of VO2 thin films deposited by pulsed laser deposition. (20th December 2017) - Umar, Z. A.
Abstract : The vanadium dioxide (VO2 ) thin films were deposited on silicon (100) substrate using the pulsed laser deposition technique. The thin films were deposited at different substrate temperatures (500°C, 600°C, 700°C, and 800°C) while keeping all the other parameters constant. X‐ray diffraction confirmed the crystalline VO2 (B) and VO2 (M) phase formation at different substrate temperatures. X‐ray photoelectron spectroscopy analysis showed the presence of V 4+ and V 5+ charge states in all the deposited thin films which confirms that the deposited films mainly consist of VO2 and V2 O5 . An increase in the VO2 /V2 O5 ratio has been observed in the films deposited at higher substrate temperatures (700°C and 800°C). Scanning electron microscope micrographs revealed different surface morphologies of the thin films deposited at different substrate temperatures. The electrical properties showed the sharp semiconductor to metal transition behavior with approximately 2 orders of magnitude for the VO2 thin film deposited at 800°C. The transition temperature for heating and cooling cycles as low as 46.2°C and 42°C, respectively, has been observed which is related to the smaller difference in the interplanar spacing between the as‐deposited thin film and the standard rutile VO2 as well as to the lattice strain of approximately −1.2%.