Berlin 2008 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 86: Oxides and Insulators: Adsorption
O 86.5: Vortrag
Freitag, 29. Februar 2008, 10:30–10:45, MA 141
The thermal behavior of H in O-ZnO(000-1) subsurface: a HREELS study — •Hengshan Qiu, Yuemin Wang, and Christof Wöll — Lehrstuhl für Physikalische Chemie I, Ruhr-Universität Bochum, 44780 Bochum, Germany
The presence of H adatoms has pronounced effects on the structure and chemical properties of metal oxide surfaces [1]. The structure and stabilization mechanisms of the polar O-terminated ZnO(000-1) surface are still under discussion [2]. In this work, the interaction of atomic hydrogen with the O-ZnO(000-1) surface was studied using high-resolution electron energy loss spectroscopy (HREELS), thermal desorption spectroscopy (TDS) and low-energy electron diffraction (LEED). It is found that the clean, H-free O-ZnO surface exhibits a (1*3) reconstruction with one third of the surface O atoms missing, in good agreement with the results obtained by He-atom scattering (HAS)[2]. Adsorption of atomic H (or H2O) at room temperature converts the (1*3) reconstruction to (1*1) with formation of OH species. In addition, The HREELS data reveal that exposing the clean O-ZnO surface to atomic hydrogen leads to a significant broadening of the incoherent elastic peak, indicating a surface metallization as determined on the ZnO(10-10) surface [3]. The metallization is induced by hydrogen adsorbed in subsurface. Upon heating these H atoms -instead of recombinative desorption- undergo migration into the bulk.
[1] Ch. Wöll, J. Phys. Condens. Matter. 16 (2004) 2981. [2] Ch.Wöll, Prog. Surf. Sci. 82 (2007) 55. [3] Y. Wang, et al., Phys. Rev. Lett. 95 (2005) 266104.