SCANNING-TUNNELING-MICROSCOPY ON CONCAVE-SHAPED SI(100) SUBSTRATES

The surface structure, step- and terrace-width distribution of mechano-chemically prepared, concave-shaped Si(100) substrates, have been determined by scanning tunneling microscopy (STM). The as-prepared surfaces present a continuous range of local polar miscut angles Theta = 0 degrees-12 degrees and the full range of azimuthal directions. Under UHV treatment the surface breaks up into stepped surfaces with 2 X 1 and 1 X 2 reconstructed terraces. Depending on the local miscut angle Theta, three topographically different regions can be distinguished. A double-domain structure with single-layer steps is observed for Theta around 1 degrees. In [001]-like directions scaly arrangements of small terraces with both reconstructions were found. In [011]-like directions and for Theta exceeding 6 degrees, this phase is transformed into a single-domain structure where terraces are connected by double-layer steps. For intermediate Theta, a mixture of SL and DL steps was observed confirming a gradual and not abrupt transition between these phases. Well ordered high-index faces like (911) and (711) were observed for Theta exceeding 9 degrees.