CHARGE-TRANSFER AND ASYMMETRY ON GE(111)-C(2X8) STUDIED BY SCANNING TUNNELING MICROSCOPY

Scanning-tunneling-microscopy images of annealed Ge(111) show large c(2 X 8) domains with protrusions that match closely the arrangement of adatom and rest-atom dangling bonds in the simple adatom model. The unit cell, however, appears asymmetric or "buckled"; namely, the two adatoms or the two rest atoms within the unit cell show significant differences in apparent height. Both the adatom and rest-atom dangling bonds can be simultaneously observed with either bias polarity, indicating that both are partially filled. These results will be discussed in relation to the proposed charge transfer between the adatoms and rest atoms.