Thickness-dependent formation of Gd-silicide compounds

Abstract
Gd-silicide phases were investigated by x-ray diffraction. The results showed that not only one phase exists in a Gd thin-film and silicon substrate reactions. The first phase formed was hexagonal GdSi≊1.7, the second orthorhombic GdSi2. The ratio of the two phases depends on temperature of the heat treatment, and at a given temperature and time of annealing, a dependence of the thickness of the evaporated Gd layer was found. At ∼100-nm Gd thickness the dominant phase was orthorhombic GdSi2, at ∼250 nm hexagonal GdSi≊1.7. In the 300–1000-nm interval orthorhombic GdSi2 was the main component again. Rutherford backscattering analysis showed that the phases were found mixed within the layer. This thickness-dependent formation could be described with a simple model proposed by Gösele and Tu [J. Appl. Phys. 53, 3252 (1982)].