Ni silicides formation and properties in RF sputtered Ni100−xSix thin films

The temperature dependence of the electrical resistance R(T) for RF sputtered Ni100−xSix thin films (33 ≤ x ≤ 56 as determined by Rutherford backscattering spectroscopy) was measured between −190°C and the annealing temperature Ta (Ta max = 300°C). Structure investigations by X-ray diffraction revealed the preferential formation of silicide phases in as-deposited films as dependent on composition: γ-Ni5Si2 (for x = 33), δ-Ni2Si (37 ≤ x ≤ 40) and Д-NiSi2 (for x = 56). For intermediary compositions, amorphous alloys are formed. Annealing at 200 and 300°C induces crystallization of the amorphous films into the γ-Ni5Si2 phase (with Д-NiSi2 admixture). The preferential formation of silicide phases is discussed taking into account the phenomenological rule of “effective formation heat”. The temperature dependence of electrical resistance for as-deposited and annealed γ and δ polycrystalline silicide thin films exhibits a classic metallic behaviour (different from that of polycrystalline Ni thin films). The very different R(T) behaviour of as-deposited and annealed polycrystalline Д-phase is interpreted taking into account the weak localization contribution.