Ballistic electron emission microscopy was used to study individual point defects in the CoSi2/Si(111) interface of approximately 3nm-thick silicide films which had been grown epitaxially onto Si substrates by using molecular beam techniques. Clear evidence was found for the trapping of point defects at dislocations. The lateral distribution of the interfacial point defects was explained in terms of diffusion during an annealing stage of the growth process in which the sample was kept at a temperature of 640C for some 300s. A diffusion coefficient of 5.2 x 10-16cm2/s and an initial point defect density of 7.37 x 1012/cm2 were estimated for these conditions. The missing point defects next to a dislocation line were expected to be found trapped in the core of the dislocation, at a linear density of 0.66/nm. Counting of all of the point defects in several highly-resolved dislocations images indicated an occupation of 0.626/nm. The ballistic electron emission microscopic contrast that was due to a single point defect had an apparent width of about 1nm. The measurements did not yield any further information concerning the structural nature of the point defects, and it was unclear whether scattering was caused by vacancies, interstitial defects, or impurity atoms. However, the accumulation of vacancies near to the core of a dislocation line was energetically favorable.

T.Meyer, H.Von Känel: Physical Review Letters, 1997, 78[16], 3133-6