INTERFACIAL DISLOCATIONS DETECTED BY SCANNING TUNNELING MICROSCOPY

Thin films of CoSi2 have been grown on Si(III) and Si(100) by molecular beam epitaxy (MBE). We present the unexpected result that scanning tunneling microscopy (STM) is sensitive to the misfit dislocations present at the CoSi2/Si interface in the case of overcritical, relaxed layers. Even for layer thicknesses above 100 angstrom a surface contrast consisting of protruding lines which is due to the dislocations at the interface is easily visible in STM topographs. Topographic cross-sections perpendicular to these protruding lines can well be fitted to a Lorentzian with a half-width equal to the CoS2 layer thickness, i.e., the distance to the dislocation core. This effect is qualitatively explained by simple elasticity theory, but additional mechanisms have to he invoked in order to account for a quantitative explanation of the observed contrast. These measurements establish conventional STM as a viable technique for the imaging of interface dislocations.