Role of Grain Boundaries in the Conductivity of Vanadium Dioxide Thin Films

Vanadium dioxide (VO$_{2}$) single crystals undergo a structural first-order metal to insulator phase transition at approximately 68$^{\circ}$C. This phase transition exhibits a resistivity change of up to 5 orders of magnitude in bulk specimens. We observe a 2-3 order of magnitude change in thin films of VO$_{2}$ presumably due to the large number of grain boundaries in the film. The interface between grains was studied by TEM and appears amorphous. Electron energy loss spectroscopy shows VO$_{2}$ like spectra with no additional surface oxidation.