Temperature-programmed desorption (TPD) and scanning tunneling microscopy (STM) were used to probe the atomic arrangement on clean Ge(011)-c(8×10), as well as the desorption kinetics and pathways from hydrogen-adsorbed surfaces. For the TPD measurements, the samples were heated at 2 °C s-1 after adsorbing atomic deuterium at 100 °C to coverages θD ranging up to saturation. Low-energy electron diffraction (LEED) and STM show that saturation deuterium coverage results in a (1×1) structure with the surface composed of randomly distributed adatom islands. TPD spectra exhibit three second-order peaks corresponding to D2 desorption from multideuterides, adatom monodeuterides and rest-atom monodeuterides. Desorption from the multideuteride phase (with an activation energy Ea of 1.61 eV) begins at 200 °C and, by 270 °C, only the D-adatom and D-rest-atom monodeuteride phases remain. D2 begins to desorb from adatom sites (Ea = 1.76 eV) above 230 °C and from rest-atom sites (Ea = 1.83 eV) above 240 °C. From quantitative analyses of the TPD spectra, the adatom density on the clean surface is ≥0.47. This high adatom density - similar to that of Si(111)-(7×7), Si(011)-(16×2) and Ge(111)-c(2×8), all of which contain adatoms and rest atoms as primary building blocks - appears to rule out previously proposed models for the Ge(011)-c(8×10) surface structure, for which the adatom density is 0.064.
Bibliographical noteFunding Information:
The authors acknowledge the financial support of the Semiconductor Research Corporation and the Materials Science Division of the US Department of Energy under contract number DEAC0276ER01198.
All Science Journal Classification (ASJC) codes
- Condensed Matter Physics
- Surfaces and Interfaces
- Surfaces, Coatings and Films
- Materials Chemistry