Difference in charge transport properties of Ni-Nb thin films with native and artificial oxide
Journal article, 2015
Here, we report on the properties of native and artificial oxide amorphous thin film on a surface of
an amorphous Ni-Nb sample. Careful measurements of local current-voltage characteristics of the
system Ni-Nb / NiNb oxide/Pt, were carried out in contact mode of an atomic force microscope.
Native oxide showed n-type conductivity, while in the artificial one exhibited p-type one. The
shape of current-voltage characteristic curves is unique in both cases and no analogical behavior
is found in the literature. X-ray photoelectron spectroscopy (XPS) measurements were used to
detect chemical composition of the oxide films and the oxidation state of the alloy components.
Detailed analysis of the XPS data revealed that the structure of natural Ni-Nb oxide film consists
of Ni-NbOx top layer and nickel enriched bottom layer which provides n-type conductivity. In
contrast, in the artificial oxide film Nb is oxidized completely to Nb2O5, Ni atoms migrate into
bulk Ni-Nb matrix. Electron depletion layer is formed at the Ni-Nb/Nb2O5 interface providing ptype