Berlin 2012 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 31: Clean surfaces II
O 31.5: Vortrag
Dienstag, 27. März 2012, 11:30–11:45, A 060
Spectroscopy of single donors at ZnO(0001) surfaces — •Hao Zheng1, Jörg Kröger2, and Richard Berndt1 — 1Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, D-24098 Kiel, Germany — 2Institut für Physik, Technische Universität Ilmenau, D-98693 Ilmenau, Germany
ZnO has been widely investigated as a material for piezo-, micro-, and opto-electronic devices. Although the band-gap of ZnO in the wurtzite structure is as large as 3.4eV, undoped material exhibits n-type conductivity at room temperature. The conductivity has been attributed to native defects such as interstitial Zn, Zn with O vacancies, Zn with substitutional N, and H impurites. Despite its importance for applications the origin of the residual conductance is still controversial. Here, donors near the polar (0001) surface of nominally undoped ZnO were investigated with scanning tunneling microscopy at 5K. Spatially resolved spectroscopy reveals single and double charging. Equidistant peaks in spectra of ionized donors are attributed to polaron excitation. The data are consistent with doping due to Zn interstitials or complexes. Support by the DFG via SFB 855 is acknowledged.