Initial oxygen reaction on Ge(100) 2x1 surfaces

The initial stage of the interaction of the Ge(100) surface with molecular oxygen was studied by scanning tunneling microscopy. Using defect-free surface and in situ oxidation, oxygen-induced products could be unambiguously determined with atomic resolution. Two types of bright products and two types of dark products were identified. One of the bright products is a major product and it has a protrusion on top of the dimer. Since this product was observed even after annealing at 300 degrees C, it is one of the stable products. The other bright product is a bright spot at a buckled dimer and the buckling is stabilized near the product. The two dark products are similar to the missing dimer defects in filled-state images, but they appeared as bright spots in empty-slate images. These topographic images were compared with theoretical chemisorption geometries for Si(100)-O and Ge(100)-O systems.