VO2 thin films:: growth and the effect of applied strain on their resistance

In this paper we report the synthesis and properties of various vanadium oxide phases. Thin films have been prepared using conventional pulsed laser deposition (PLD). We have used both metallic V and ceramic V2O5 targets to obtain the films. With both targets we have found that it is possible to move, in a controlled way, through several of the oxide states by changing the background oxygen gas pressure during deposition. Significantly, over the range of deposition conditions investigated we only observe the occurrence of the VO2, V6O13 and V2O5. This observation is unusual because as many as thirteen oxidation states are believed to exist. The temperature and strain dependence of film resistance was also investigated. VO2 films were found to undergo their metallic to semiconducting phase transition at similar to 68 degrees C. The resistance change across this transition was found to be greater than four orders of magnitude. Further, in-plane tensile strains of 0.04% were observed to change resistance values by similar to 35% near the phase transition. (C) 1998 Chapman & Hall.