Difference in charge transport properties of Ni-Nb thin films with native and artificial oxide

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 conductivity

Structure and Thermal Properties of an Al-Based Metallic Glass-Polymer Composite

A composite material based on polyethylene terephthalate (PET, about 1% by mass) and Al85Y8Ni5Co2 metallic glass was obtained by mechanical alloying and consequent spark plasma sintering. The spark plasma sintering was performed at a temperature near to the super cooled liquid region of the metallic glass. Mechanical properties and the structural characterization of the composite material were obtained. It was conceived that composite samples (Al85Y8Ni5Co2/PET) have a better thermal conductivity in comparison with pure PET samples. The formation of the crystalline phases causes degradation of physical properties. It was calculated that the activation energy for crystallization of the Al85Ni5Y8Co2 metallic glass is higher than that of the other types of metallic glasses (Mg67.5Ca5Zn27.5 and Cu54Pd28P18) used for composite preparation previously. This denotes a good thermal stability of the chosen metallic glass