Thin films of thermochromic vanadium dioxide have been the subject of intensive research in recent years year due to their postulated use as "intelligent" window coatings. The usefulness of such technology depends on a semi-conducting to metal transition with an associated change in infra-red optical properties. This exact nature of this transition depends on a large number of factors such as doping, crystallite size, strain, crystallographic orientation etc. In this paper we discuss the nature of these factors with a particular focus on how the application of electric fields in the deposition affects crystallite size and film strain with reference to recent results.