Hydrogen adsorption configurations on Ge(001)probed with STM

The adsorption of hydrogen on Ge(001) has been studied with scanning tunneling microscopy at 77 K. For low doses (100 L) a variety of adsorption structures has been found. We have found two different atomic configurations for the Ge-Ge-H hemihydride and a third configuration that is most likely induced by the dissociative adsorption of molecular hydrogen. The Ge-Ge-H hemihydride is either buckled antiparallel or parallel to the neighboring Ge-Ge dimers. The latter configuration has recently been predicted by M. W. Radny et al. [J. Chem. Phys. 128, 244707 (2008)], but not observed experimentally yet. Due to the presence of phasons some dimer rows appear highly dynamic.