Berlin 2005 – scientific programme
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O: Oberflächenphysik
O 20: Organische Dünnschichten II
O 20.5: Talk
Saturday, March 5, 2005, 11:45–12:00, TU EB202
Engineering of GaAs (100) surface with 4’-substituted aromatic self-assembled monolayers — •Michael Zharnikov1, Andrey Shaporenko1, Adlkofer Klaus2, Avi Ulman3, Michael Grunze1, and Motomu Tanaka2 — 1Angewandte Physikalische Chemie, Universität Heidelberg, Im Neuenheimer Feld 253, D-69120 Heidelberg, Germany — 2Lehrstuhl für Biophysik E22, Technische Universität München, James-Franck-Strasse, D-85748, Garching, Germany — 3Department of Chemical Engineering, Polytechnic University, Brooklyn 11201, New York, USA
High-resolution x-ray photoelectron spectroscopy and near edge x-ray absorption fine structure spectroscopy were applied to characterize GaAs (100) surface engineered by self-assembled monolayers (SAMs) of 4’-substituted aromatic molecules: 4’-methyl-4-mercaptobiphenyl (CH3-BPT) and 4’-hydroxy-4-mercaptobiphenyl (OH-BPT). These molecules were found to form ordered and densely packed SAMs on GaAs, which were able to protect the substrate from degradation under ambient conditions. The molecular attachment in the SAMs occurs over As-thiolate bond while the intact aromatic backbones have an upright orientation with average tilt angles of 31.0∘ and 37.2∘ for CH3-BPT and OH-BPT films, respectively. The difference in the tilt angle is attributed to a higher (by 7-10%) packing density of the former SAM, suggesting that the character of 4’-substitution affects the SAM quality in the case of GaAs substrate.