SCANNING-TUNNELING-MICROSCOPY OF CHEMICALLY CLEANED GERMANIUM(100) SURFACES

The effects of HF/H2O2 etching, UV/ozone oxidation, and ultrahigh vacu um annealing on the composition and structure of Ge(100) surfaces has been studied by X-ray photoemission and scanning tunneling microscopy. Our results indicate that any carbon impurities left on the surface a fter the etch and oxidation steps cannot be completely removed by heat ing in vacuum. On flat Ge(100), carbon pins the steps in place during annealing. Germanium terraces pile up at these locations, producing a mountain-and-valley structure between 20 and 30 atomic layers in heigh t. On Ge(100) 9 degrees off-axis, step pinning by carbon generates a f aceted surface covered with V-shaped ridges. (C) 1998 Published by Els evier Science B.V.