SCANNING TUNNELING MICROSCOPY AND SPECTROSCOPY OF CLEAVED AND ANNEALED GE(111) SURFACES

The scanning tunneling microscope (STM) is used to study the structural and electronic properties of cleaved and annealed Ge(111) surfaces. High quality cleaves, with typical step separations of 2000 angstrom, are obtained. After annealing at 270-degrees-C, the cleaved 2 x 1 surface converts into a well-ordered c(2 x 8) reconstruction. The major source of disorder in a single c(2 x 8) domain is found to be extra rows of atoms which result in a local 2 x 2 stacking arrangement. The difference in surface atom density between 2 x 1 and c(2 x 8) leads to the formation of bilayer-deep holes in the surface. Spectroscopy and voltage-dependent imaging of the c(2 x 8) structure is performed, and is compared with previous results. The simple adatom model for the c(2 x 8) structure is confirmed.