STRESS-INDUCED SHAPE TRANSITION OF COSI2 CLUSTERS ON SI(100)

CoSi2 clusters on a Si(100) surface grow in a square shape at first, b ut at a critical size a shape transition to clusters with large aspect ratios occurs. Each cluster is connected to an implanted layer of cob alt by a thermally induced defect that serves as a diffusion channel. In this novel growth mode the existing clusters can grow with a contin uous supply of cobalt while cluster-cluster interaction is prevented f rom becoming a dominant factor to the cluster shape as a result of the large distance between defects. Our data are in good agreement with c alculations on the balance between surface and interfacial energies on the one hand and stress relaxation due to an elastic distortion of th e substrate on the other.