Observation of misfit dislocations in epitaxial CoSi2/Si (111) layers by scanning tunneling microscopy

The surfaces of epitaxial CoSi2 layers grown on Si(111) have been examined by scanning tunneling microscopy (STM) in ultrahigh vacuum. The onset of strain relaxation above the critical thickness of about 40 Å has been monitored by STM for the first time. This relaxation takes place by the formation of a honeycomb network of partial dislocations lying in the interface plane. An associated network of protruding lines has been detected in STM topographs for film thicknesses up to 104 Å. The topographic cross sections perpendicular to the lines are found to have a Lorentzian shape with a height of 0.6 Å and a half-width equal to the layer thickness. Our analysis suggests that similar effects should be observable for a wider class of heteroepitaxial systems.