Strain-induced shape transition of VSi₂ clusters on Si(111)

We investigated the growth and shape of vanadium silicide clusters on Si(111) using scanning tunneling microscopy, atomic force microscopy and scanning electron microscopy. The deposition of 8 monolayers of vanadium on Si(111) and subsequent annealing at 1200 K leads to the formation of large elongated VSi₂ clusters. This is in marked contrast to the deposition of submonolayer amounts of V where the VSi₂ islands have a compact shape. The shape transition can be explained by a competition between edge formation and strain relaxation energy terms. The VSi₂ clusters, which are aligned along the three high symmetry directions of the Si(111) surface and surrounded by a denuded zone, form a two-dimensional network.