Nickel silicide is an inorganic compound consisting of nickel and silicon atoms. The crystal structure of Nickel silicides varies depending on the ratio of Si to Ni. The crystal types of Ni2Si, NiSi, and NiSi2 are Orthorhombic, Orthorhombic, and Cubic, respectively. The figure below shows the differences between the NiSi2 and Si lattices. These differences lead to the possibility of multiple atomic structures at their interfaces. This difference in crystal symmetry results in some defects at some of the silicide/Si interfaces. the lattice constant of NiSi2 is approximately 0.4% smaller than that of Si.