Influence of deposition process and substrate on the phase transition of vanadium dioxide thin films

The abrupt changes in structural, electronic and optical properties that accompany the vanadium dioxide (VO2) phase transition make it a promising material for a wide range of thin-film applications in electronics,photonics and plasmonics. Several physical vapor-deposition techniques are used by various research groups, but until now there has been no systematic comparison of the three most common methods electron beam evaporation, pulsed-laser deposition and sputtering covering the most common substrates. Here we explore the influence of substrate, deposition process and annealing time at 450 degrees C on the phase transition properties and morphology of thin VO2 films. Films deposited by rf magnetron sputtering have the same structure on glass, silicon and sapphire substrates and are stable for 90 mm of annealing. In contrast, the structure of films deposited by electron beam evaporation and pulsed laser deposition depends heavily on the substrate. Dewetting plays a prominent role in the evolution of film structure and the phase transition properties for films deposited on silicon and glass are unstable for 90 min annealing. The epitaxial relationship between VO2 and sapphire stabilizes the phase transition contrast for all deposition processes and annealing times. Performance as measured by switching contrast is maximized for all deposition processes with 10 mm of annealing. (C) 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.