Europhys. Lett.
Volume 67, Number 5, September 2004
Page(s) 827 - 833
Section Condensed matter: structure, mechanical and thermal properties
Published online 01 August 2004
Europhys. Lett., 67 (5), pp. 827-833 (2004)
DOI: 10.1209/epl/i2004-10116-7

Evidence for strong interaction of PTCDA molecules with defects on sulphur-passivated $\chem{GaAs(100)}$

G. Salvan and D. R. T. Zahn

Institut für Physik, Halbleiterphysik, Technische Universität Chemnitz D-09107, Chemnitz, Germany

(Received 5 February 2004; accepted in final form 18 June 2004)

Raman spectroscopy was employed to investigate the initial stage of interface formation between 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) molecules and sulphur-passivated $\chem{GaAs(100)}$ surfaces. Monitoring the Raman spectra for submonolayer coverage as well as after annealing above the desorption temperature of PTCDA reveals the presence of a $\chem{C}$- $\chem{H}$ mode which is shifted by 13 $\un{cm^{-1}}$ towards lower frequency compared to its value in bulk PTCDA. The molecules remaining at the surface after annealing are proposed to interact with surface defects predominantly induced by the dopant atoms. This proposal is supported by density-functional theory calculations considering the interaction of dopant atoms with single molecules.

68.60.-p - Physical properties of thin films, nonelectronic.
68.35.Dv - Composition, segregation; defects and impurities.
78.30.Jw - Organic compounds, polymers.

© EDP Sciences 2004