Study of solid-phase reactions in multilayered Ni/Si films by a method of a spectral ellipsometry

The solid-state reactions in the Ni/Si multilayered films (MLF) with overall compositions of Ni0.67Si0.33, Ni0.50Si0.50, and Ni0.33Si0.67, which are induced by ion-beam mixing and thermal annealing, are studied by using traditional structural X-ray diffraction methods as well as spectroscopic ellipsometry tool. Mixing is performed with Ar+ ions of an energy of 80 keV and a dose of 5x10(16) Ar+/cm(2). As shown, ion-beam mixing induces the structural changes in the Ni/Si MLF, which cannot be detected by X-ray diffraction tools, however, confidently may be recognized by the optical methods. Thermal annealing of the Ni/Si MLF with an overall composition of Ni0.50Si0.50 and Ni0.33Si0.67 causes the formation of the first eta-NiSi phase at the temperature (670 K) of annealing for all the compositions. The first traces of the NiSi2 phase on the background of the eta-NiSi phase are detected in the Ni/Si MLF by X-ray diffraction tools after their annealing at 1070 K, while according to the optical results, the NiSi2 is a dominant phase for the low-temperature annealing Ni/Si MLF with an overall composition of Ni0.33Si0.67.