Origin of the inhomogeneous nanoscale resistivity in chromium doped VO.

Chromium doped VO polycrystalline thin films typically consist of conductive grains separated by insulating grain boundaries. We investigate the origin of the spatially inhomogeneous resistivity in these films and find no qualitative differences between doped and undoped films, or for different oxygen stoichiometries. By a combination of conductive atomic force microscopy, high-resolution transmission electron microscopy and nanoscale elemental mapping, we show that the inhomogeneity is due to the formation of amorphous or poorly crystallized regions at the grain boundaries. Both the distribution of the dopants and the local oxygen stoichiometry appear to be very homogeneous, and therefore do not contribute to the inhomogeneous conductivity.