Dresden 2003 – wissenschaftliches Programm
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HL: Halbleiterphysik
HL 19: Organische Halbleiter I
HL 19.9: Vortrag
Dienstag, 25. März 2003, 13:00–13:15, BEY/81
SERS and DFT studies of biomolecular layers on silicon surfaces — •S.D. Silaghi1, G. Salvan1, T.U. Kampen1, M. Friedrich1, R. Scholz1, H. Angermann2, and D.R.T. Zahn1 — 1Institut für Physik, Technische Universität Chemnitz, D-09107 Chemnitz, Germany — 2Hahn-Meitner-Institut, Abt. Silizium Photovoltaik, D-12489 Berlin, Germany
Among biomolecular systems, DNA bases are particularly interesting in view of achieving conductive molecular nanowires. Here, surface-enhanced Raman spectroscopy (SERS) is used to investigate ultrathin guanine and cytosine films on silicon substrates. Monolayers of guanine and its counterpart cytosine were prepared by organic molecular beam deposition (OMBD) under UHV conditions on H-terminated flat and vicinal Si(111) surfaces. Onto these biomolecular layers silver is evaporated leading to an enhancement of the Raman signal. The spectral changes observed in SERS spectra below 730cm−1 in the out-of-plane region of CH and NH deformation modes are related to a change in the morphology of thin cytosine layers compared to thick layers around 450nm. On vicinal H-Si(111) surfaces miscut 6 o toward [-1 -1 2] guanine and cytosine monolayers are found to be in a different molecular arrangement than on flat H-Si(111) surfaces. DFT/B3LYP calculations using the LANL2DZ basis set were carried out for silver-cytosine and silver-guanine complexes with Gaussian 98.