Effect of thickness on the film strain and metal-semiconductor transition of VO$_{2}$ thin films

Many applications of VO$_{2}$ will benefit from the extensive tunability of the Metal to Semiconductor Transition (MST) of VO$_{2}$, which is very sensitive to the film strain and the oxygen stoichiometry [1,2]. Reactive Bias Target Ion Beam Deposition was used to deposit epitaxial VO$_{2}$ thin films on (100), (011), and (001) TiO$_{2}$ substrates, and highly textured VO$_{2}$ on $c$-Al$_{2}$O$_{3}$ with thicknesses in the range of 5-17 nm. X-ray diffractometry confirmed the single-phase nature of the VO$_{2}$ films, and was also used to determine the lattice parameters. Due to the substrate clamping effect, there are very large strains introduced (up to 3.4{\%}), that affect the transition temperatures (T$_{\mathrm{MST}})$. For the 5nm VO$_{2}$/(100) TiO$_{2}$, T$_{\mathrm{MST}}$ is raised above 430 K, which is much higher than in previous reports. The resistivity of this sample changed about 4 orders of magnitude during the transition from a semiconductor to a metal. \\[4pt] [1] S Kittiwatanakul, et al., Journal of Applied Physics 114 (5), 053703-053703-5 (2013) \\[0pt] [2] K. G. West, et al. Journal of Vacuum Science {\&} Technology A 26(1): 133-139 (2008)