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AKB: Biologische Physik

AKB 50: Poster Session "Biological Physics"

AKB 50.131: Poster

Freitag, 12. März 2004, 10:30–13:00, B

Biophysical applications of chemically engineered GaAs-based semiconductors — •Klaus Adlkofer¹, Daniel Gassul¹, Andrey Shaporenko², Michael Zharnikov², Michael Grunze², Abraham Ulman³, and Motomu Tanaka¹ — ¹Lehrstuhl für Biophysik E22, Technische Universität München — ²Lehrstuhl für Angewandte Physikalische Chemie, Universität Heidelberg — ³Polytechnic University Brooklyn, New York, USA

Stable chemical engineering of stoichiometric GaAs [100] surfaces was achieved by deposition of 4-′-substituted-4-mercaptobiphenyl terminated with −H, −CH₃ and −OH. Topography of the engineered surface was studied by atomic force microscopy (AFM). Orientation of the molecules was evaluated by near edge x-ray fine structure (NEXAFS) spectroscopy and Fourier transformed infrared spectroscopy (FTIR), and the covalent binding between the thiolate and surface arsenide was confirmed by high-resolution x-ray photoelectron spectroscopy (HRXPS). Surface free energies of the engineered surfaces were calculated from contact angle measurements. Current-voltage scans showed the drastic suppression of oxidation and reduction by coating of GaAs. Electrochemical properties of the engineered GaAs in aqueous electrolytes were measured by impedance spectroscopy, demonstrating that all three types of mercaptobiphenyls can form stable monolayers with high electric resistances, R>2MΩ cm². The surface engineering method established here allows for control of surface free energies towards deposition of model biomembranes on GaAs-based device surfaces.