SCANNING-TUNNELING-MICROSCOPY ON QUENCHED SI(111) SURFACES

Scanning tunnelling microscopy has been applied to study Si(lll) surfa ces quenched from sublimation temperatures. Morphological instability of the surface upon sublimation results in step bunching and occasiona lly in macroscopical roughness. At the same time creation of atomicall y flat terraces up to 20 mu m wide is possible. On such terraces trian gular structureless islands with a poorly reconstructed surface undern eath were observed whereas the rest of the surface was 7 x 7 reconstru cted. According to the introduced model, this may be a result of compr ession of the adatom gas in the [11 ($) over bar 2] direction by growi ng 7 x 7 reconstruction spots. This compression leads to a local incre ase of the adatom concentration in the unreconstructed areas and final ly to a push-out of the excess atoms which remain unreconstructed.