Vertical element redistribution in Ni78B11Si11 amorphous films deposited on Si as revealed by scanning Auger microprobe and cross-sectional transmission electron microscopy

The vertical element redistribution in Ni78B11Si11 amorphous films deposited on Si wafers was surveyed by means of scanning Auger microprobe and cross-sectional transmission electron microscopy in order to obtain a better understanding of the crystallization process of amorphous alloys. The diffusion of Si and Ni atoms across the film-substrate interface commencing at ∼250 °C drove B atoms toward the surface, thereby dividing the film into Si- and B-rich regions. The crystallization started at ∼300 °C in the Si-rich region, and the crystallized zone grew with increasing temperature, until the B-rich outer region was transformed into a polycrystalline state at ∼350 °C. These findings indicated that the crystallization temperature was a strong function of compositional structure, thus allowing us to conclude that a local compositional variation is generally a precondition for the nucleation of the crystalline phase in the amorphous matrix.