LATTICE MATCHING PERIODIC INTERFACIAL DISLOCATION NETWORK IN SURFACTANT-MEDIATED GROWTH OF GE ON SI(111)

The use of Sb as surfactant allows to grow continuous and smooth Ge fi lms free of defects and of arbitrary thickness on Si(111)-substrates. The lattice mismatch, of 4.2% is adjusted by a periodic network of dis locations in the interface plane. The strain fields of the dislocation s give rise to an elastic deformation of the surface of less than 0.1 nm, which results in a spot splitting in low energy electron diffracti on. The exact shape of the deformation and thus the arrangement of the dislocations at the interface are deduced from the intensity variatio n of the satellite spots with electron energy. The dislocations do not intersect in one point but form an extended node with a size of 1.8 n m. From the shape of the satellite spot profiles the distance variatio ns of the dislocation network are derived. Therefore the lateral latti ce constant fluctuates about +/-1%, although the Ge film shows on aver age the Ge bulk lattice constant. With increasing film thickness the s train fields of the dislocations interact more and more resulting in a higher regularity of the dislocation spacings. The lattice constant o f the Ge film is well defined only for thickness exceeding about 10 nm .