Electronic Structure and Electrical Conductivity of Amorphous Ni–Si Alloy Films

The Ni x Si 100- x system forms a homogeneous amorphous phase over wide ranges of composition (0≦ x ≦34 and 63≦ x ≦73) when the alloy is deposited on a substrate by sputtering at ambient temperature. The electrical conductivity of the amorphous alloy changes characteristically with Ni concentration from a semiconductor-like temperature dependence to a metallic one, the transition taking place between 10.4 and 16.6% Ni. UPS valence band spectra show that the density of states at the Fermi level is minimal below about 7% Ni, but emerges abruptly above this concentration. The relationship between the electrical transport properties and the electronic structure of the amorphous alloys is discussed in three characteristic regions of the Ni concentration.