Surface-energy triggered phase formation and epitaxy in nanometer-thick Ni_1-xPt_x silicide films

The formation of ultrathin silicide films of Ni_1-xPt_x at 450–850 °C is reported. Without Pt (x=0) and for t_Ni≪4 nm, epitaxially aligned NiSi_2-y films readily grow and exhibit extraordinary morphological stability up to 800 °C. For t_Ni≥4 nm, polycrystalline NiSi films form and agglomerate at lower temperatures for thinner films. Without Ni (x=1) and for t_Pt=1–20 nm, the annealing behavior of the resulting PtSi films follows that for the NiSi films. The results for Ni_1-xPt_x of other compositions support the above observations. Surface energy is discussed as the cause responsible for the distinct behavior in phase formation and morphological stability.