Oxidation and hydrogenation of SiGe(001)-2 × 1 at room temperature and in situ annealing: A synchrotron radiation photoemission study

Schematic drawings of (a) atomic O on SiGe(001)-2×1, and (b) atomic H on SiGe(001)-2×1 bonding configuration. [Display omitted] •The electronic structure of atomic O/H on SiGe(001)-2 × 1 at the elevated temperature.•The O atoms are positioned at the backbond of the down-atom Ge dimer at RT.•Heat causes the Si atoms become oxidized, and no O atoms remains at the Ge atoms.•The H atoms are positioned at the backbonds of the dimerized Ge atoms.•Upon annealing, half of the Ge-Ge dimers are wiped off. This study used high-resolution synchrotron radiation photoemission to investigate the epi SiGe(001)-2 × 1 surface that was exposed to atomic oxygen and hydrogen at room temperature, followed by in situ annealing at 500 °C. The SiGe(001)-2 × 1 surface that was grown by molecular beam epitaxy (MBE) was terminated with buckled Ge–Ge dimers, where the Ge dimers exhibited great similarity compared to those on epi Ge(001)-2 × 1. The exposure of atomic oxygen started from as low as 0.1 L up to 500 L, although the interfacial reaction practically stopped at 10 L of exposure. Atomic oxygen bonded only with the up-dimer atoms, while the atomic hydrogen passivated both dimerized atoms. Upon annealing, the GeOx oxides and GeHx hydrides disappeared completely, and the Ge region became similar to that of the clean surface. However, over half of the Ge–Ge dimers were removed from the surface after annealing in both interfaces. Heat caused the oxygen atoms in GeOx to move over to the Si region, thereby giving rise to 1+ to 4+ charge states of SiOx, which was similar to the case of the oxidation of c-Si(001)-2 × 1. The catalytic effect of Ge decreased the elevated temperature to, at most, 500 °C.