THEORETICAL-STUDY OF STRAIN-INDUCED STEP CONFIGURATION CHANGES ON VICINAL SI(001) BY THE GROWTH OF GE

The initial stage of growing Ge on single-domain vicinal Si(001) with a large angle of misorientation has been studied theoretically by the modified Keating model and compared with RHEED and STM experiments. Th e experimentally observed conversion from the DB step configuration, w here all dimer rows are normal to the step edges, to a DA-like step co nfiguration, where dimer rows on one terrace are parallel to the step edges, at Ge coverages larger than 1 ML is identified by our calculati ons. Our results show that this DA-like step is in fact a pair of step s of single atomic height: SA+SB, with a very wide SA terrace and an S E tooth of about 10 Angstrom. This new step configuration is energetic ally favoured over DA and DB step configurations.