Morphology and growth of hafnium silicide on Si(1 1 1)

Abstract

The structure and growth of hafnium silicide on Si(111) were studied by scanning tunneling microscopy (STM). Hafnium was deposited by electron beam evaporation onto a clean Si(111) surface under UHV-conditions. The sample was heated in several steps up to 900°C. Upon annealing a growth of elongated nanosized structures was observed. These hafnium silicide islands were found to grow along three main directions, aligned to the symmetry of the (111) surface. As a result, we found that the morphology of these silicide islands is affected by the annealing temperature. Overlapping elongated structures form upon annealing at 450°C. First isolated islands were found at 650°C. The distribution of these islands is equivalent for the three different main directions of the (111) surface. In comparison to the homogeneous distribution the growth of length, width, and height of the stripes starts at different temperatures for the different orientated stripes. With increasing island volume the number density of islands decreases. An analysis of the mean coverage was performed which indicated a possible decrease of the amount of hafnium on the surface. It was found that step edges have no apparent influence on the island distribution.