Dresden 2011 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 42: Focussed Session: Inorganic/Organic Semiconductor Hybrid Structures II
HL 42.2: Invited Talk
Tuesday, March 15, 2011, 14:45–15:15, POT 151
Electrostatic Field Driven Alignment of Organic Oligomers on ZnO Surfaces — •Fabio Della Sala1, Sylke Blumstengel2, and Fritz Henneberger2 — 1Nanoscience Institute (CNR), Via per Arnesano, 73100 Lecce — 2Institut fuer Physik, Humboldt-Universitaet zu Berlin, Newtonstrasse 15, 12489 Berlin, Germany
We present a theoretical study on the physisorption process of organic oligomers on the ZnO(1010) surface. Using first-principles density-functional theory and non-empirical embedding methods, we find that both in-plane location and orientation of the molecules are completely determined by the coupling of their quadrupole moments to the periodic dipolar electric field present at the semiconductor surface. The adsorption is associated with the formation of a molecular dipole moment perpendicular to the surface, which bears an unexpected linear relation to the molecule-substrate interaction energy. Long oligomers such as sexiphenyl become well-aligned with stabilization energies of several 100 meV along rows of positive electric field, in full agreement with recent experiments. These findings define a new route towards the realization of highly-ordered self-assembled arrays of oligomers/polymers on ZnO(1010) and similar surfaces.