Regensburg 2019 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 61: Semiconductor Surfaces: Adsorption and Reactivity
O 61.1: Vortrag
Mittwoch, 3. April 2019, 15:00–15:15, H25
Atomic structure of As-modified Si(100) surfaces prepared in MOCVD ambient — •Agnieszka Paszuk1, Oleksandr Romanyuk2, Oliver Supplie1, Manali Nandy1, Peter Kleinschmidt1, and Thomas Hannappel1 — 1Institute for Physics, University of Technology, Ilmenau, Germany — 2Institute of Physics, Academy of Sciences of the Czech Republic, Prague, Czech Republic
For highly efficient III-V-on-Si tandem solar cells it is crucial to avoid defects known as antiphase boundaries at the III-V/Si interface by preparing the Si(100) surface with double-layer (DL) steps. While preparation of the DL-stepped Si(100) surfaces in As-rich metalorganic chemical vapor deposition (MOCVD) ambience has been investigated, their surface structure is still not fully understood. Here, the DL-stepped Si(100) surfaces are prepared in As-rich MOCVD ambience and the entire process is monitored by optical in situ spectroscopy. The Si:As surfaces are investigated by surface-sensitive techniques in ultra-high vacuum. With scanning tunneling microscopy (STM), we observe different Si:As surface structures in dependence on the substrate miscut and preparation routes. The low-offcut Si(100):As surfaces exhibit evenly spaced, atomically flat terraces with a random distribution of darker and brighter areas, which stem from a different local electronic structure. STM scans of vicinal Si(100):As surfaces show zig-zag chains and asymmetrical protrusions. Density functional theory calculations predict that, in H2 ambient, the commonly assumed As-As dimer termination on top of Si(100) is not energetically favorable and the surface structure strongly depends on the H and As chemical potentials.