${\mathrm{H}}_2$O adsorption on Ge(100): An angle-resolved photoelectron spectroscopy study

The adsorption of ${\mathrm{H}}_2$O on Ge(100)2×1 was studied with angle-resolved photoelectron spectroscopy. The surface was exposed to ${\mathrm{H}}_2$O at 160 K. The sample was then heated to 300 K where the measurements were performed. The surface band structure was mapped in the [010] direction. We find six bands that we assign to a surface-adsorbate structure. One band with binding energy in the region 4.6–4.9 eV is assigned to the Ge-H bond. Another band dispersing between 5.6 and 5.8 eV is assigned to the Ge-OH bond. The results agree with models where the ${\mathrm{H}}_2$O is adsorbed dissociatively across the Ge-Ge dimers as H and OH on this surface at 300 K. Bands assigned to the H and OH groups disperse in momentum-energy space and we conclude that there is some long-range ordering within the adsorbate layer.