Conductivity of r.f.-sputtered Ni 100 − x −Si x thin films with 33 ⩽ x ⩽ 77 at.%

Abstract

The temperature dependence of the electrical resistance of r.f.-sputtered Ni-Si thin films with variable Si content in the range 33–77 at.% (as determined by Rutherford backscattering spectroscopy) was measured between −190 °C and the annealing temperature Tt (Ttmax = 300 °C). The as-deposited films were investigated by X-ray diffraction and transmission electron microscopy, and were found to exhibit an amorphous structure (different from that of amorphous Si), except those films with a composition favourable for silicide formation. The temperature dependence of the conductivity of these films is interpreted in the framework of the weak localization model and electron-electron interactions. Annealing at 300 °C brings about a transformation from an amorphous structure into a microcrystalline structure comprising different silicides, whose electrical resistance displays a classical metallic temperature dependence, except for the sample with x = 77 at.%, which remains amorphous, although its conductivity increases with temperature.