Low temperature formation and evolution of a 10 nm amorphous Ni-Si layer on [001] silicon studied by in situ transmission electron microscopy

We investigated low temperature formation of a 10 nm thick amorphous Ni-Si layer after room temperature deposition of a 7 nm Ni layer on [001] Si, by in situ transmission electron microscopy analyses. Instead of a conventional time sequence of phases or an immediate formation of NiSi2 domains, annealing at 220 oC promotes Ni diffusion through a thin interfacial amorphous layer, formed during deposition, into the Si lattice until the entire supply of pure Ni atoms is consumed. High concentration nickel diffusion induces a crystalline-to-amorphous transformation of the original silicon lattice. Further increasing the temperature, in the range between 300 and 350 oC, causes crystalline NiSi2 domains to nucleate and grow within the amorphous matrix.