Kinetics of shift of individual interfaces in Ni/Si system during low temperature reactions

• Reaction in nanocrystalline-Ni/amorphous Si or Si(1 0 0) systems at low temperature.
• Shift of individual interfaces of reaction layer was determined in very early stage.
• Kinetics of shrinkage of nanocrystalline Ni and Si layers follows parabolic law.
• Formation of NiSi2 in the amorphous Si is due to high diffusivity of Ni.

Nanocrystalline Ni(20 nm)/crystalline-Si and Ni(20 nm)/amorphous-Si systems were heat treated at 453 K and 473 K for 0.25–2 h. The formation of the reaction layer at the interface and the positions of the individual interfaces were followed by depth profiling using Secondary Neutral Mass Spectrometry and a profilometer. The kinetics of the shrinkage of the initial nanocrystalline Ni film and the Si layer, as well as the average growth kinetics of the product layer containing Ni2Si and NiSi phases, were determined in the very early stage of the solid state reaction. The kinetics of the Si and Ni shrinkage followed the parabolic growth law in both systems i.e. the change of the thicknesses were proportional to t1/2. In systems with a-Si, at longer annealing times, a layer with composition of about 40% Ni was developed suggesting the formation of the NiSi2. This was interpreted by the relatively high diffusivity of Ni in a-Si. Results on the effect of Pt on the enhanced homogeneity of the NiSi phase formed as well as on the growth kinetics are also presented.

Shrinkage of Ni (X) and Si (Y) versus the annealing time at 453 K reveals the parabolic kinetics in all cases; shrinkage of a-Si is faster than that of c-Si due to the high diffusivity of Ni in a-Si.Figure optionsDownload as PowerPoint slide