AMORPHOUS ALLOY FORMATION AND THICKNESS DEPENDENT GROWTH OF GD-SILICIDES IN SOLID-PHASE THIN-FILM REACTION

The formation of amorphous and equilibrium phases was investigated dur ing the solid-phase reaction of Gd thin film with (111) and (100) orie nted Si substrate as a function of thickness and annealing by X-ray di ffraction, Rutherford backscattering and transmission electron microsc opy. For Gd films thinner than 30 nm, the phase formation was affected by the substrate orientation. At low temperature (320 degrees C), amo rphous phase developed on Si(100). At higher temperatures epitaxial he xagonal GdSi1.7 was found on Si(111), while on Si(100), epitaxial orth orhombic GdSi2 was formed. For thicker gadolinium films on Si(111), a conventional diffusion-reaction process appeared. The hexagonal GdSi1. 7 phase formed first and then transformed to the second phase (orthorh ombic GdSi2). The ratio of these phases could be described by a model. On Si(100) substrate at each thickness and annealing, only orthorhomb ic GdSi2 phase was formed. The phase formation depended on the time an d temperature of the annealing and even on the initial Gd Nm thickness and substrate orientation. (C) 1998 Elsevier Science S.A.