Dresden 2014 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 37: Posters: Plasmonics, Electronic Structure and Spin-Orbit Interaction, Semiconductor and Insulator Surfaces, Nanostructures
O 37.74: Poster
Dienstag, 1. April 2014, 18:30–22:00, P2
Liquid Crystal Adsorption on Lithium Niobate (0001) Surfaces — •Christian Braun, Simone Sanna, Eva Rauls, and Wolf Gero Schmidt — Lehrstuhl für Theoretische Physik, Universität Paderborn, Paderborn, Germany
LiNbO3 (LN) is a man-made ferroelectric with a extraordinary high spontaneous polarization of 0.7 C/m2. The polarization creates a net electric field outside of the LN crystal, which can be locally patterned by switching ferroelectric domains. This opens the possibility for selective molecular adsorption, in particular of polarizable molecules, at the LN surface. Liquid crystals are highly interesting adsorbates, as their optical properties are easily manipulated by electrical or magnetic fields. Indeed, they are currently employed for the realization of modern displays, as well as in other optic and opto-electronic devices. Therefore, the detailed knowledge of the adsorption mechanisms of liquid crystal on LN, as well as the understanding of the influence of the ferroelectric substrate on the molecular ordering, would be highly desirable. In order to model the interaction of liquid crystals with ferroelectric surfaces, we have investigated the adsorption of 4-n-octyl-4′-cyanobiphenyl (8CB) molecules at the LN(0001) surfaces from first-principles. The adsorption energy and configuration are found to be both strongly polarization and coverage dependent. Van der Waals interactions, accounted for by Grimme-type corrections to the total energy, are found to yield a major contribution to the bond strength and influence the adsorbate orientation.