High resolution infrared spectroscopy of adsorbates on semiconductor surfaces: Hydrogen on Si(100) and Ge(100).

The structure of the hydrogen-saturated Si(100) and Ge(100) surfaces is studied by means of high resolution surface infrared spectroscopy. The stretching vibrations (symmetric and antisymmetric) of the monohydride, characterized by a Si-Si dimer and one H per Si, and of the dihydride, characterized by two H per Si, are identified by polarized measurements. We find that the Si(100) surfaces saturated with H at room temperature, characterized by a (1x1) LEED pattern, are made up of a disordered arrangement of subunits formed of both mono- and di-hydrides. In contrast, the H-saturated Ge(100) surface, characterized by a faint (2x1) LEED pattern, consists uniquely of monohydride, with no dihydride present.