SCANNING-TUNNELING-MICROSCOPY AND LOW-ENERGY-ELECTRON DIFFRACTION STUDY OF THE FORMATION OF A ROOT-3X-ROOT-3R30-DEGREES RECONSTRUCTION ON THE HYDROGEN ETCHED SI(111) 1X1 SURFACE

The Si(111) 7 X 7 surface is exposed at room temperature to atomic hyd rogen and studied with scanning tunneling microscopy (STM) and low ene rgy electron diffraction (LEED) in ultrahigh vacuum. For increasing ex posures, the LEED pattern of the surface changes in well defined steps to a 1 X 1 pattern. The STM images of the 1 X 1 surface appear rough and disordered. The 1 X 1 pattern and rough surface are consistent wit h an etching;of several surface layers by the atomic hydrogen. Heating the 1 X 1 surface to 560 degrees C and cooling to room temperature pr oduces a surface with a root 3 X root 3R30 degrees LEED pattern. The S TM images of this surface are consistent with a distribution of adatom s on an ideal Si(111) surface. Further heating results in a 7 X 7 surf ace. (C) 1997 American Vacuum Society. [S0734-211X(97)02605-X].