Regensburg 2016 – scientific programme
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O: Fachverband Oberflächenphysik
O 19: Semiconductor Substrates: Structure, Adsorption and Growth
O 19.6: Poster
Monday, March 7, 2016, 17:00–19:30, Poster A
High Resolution Electron Energy Loss Spectroscopy of Ammonia Adsorbed on a Water Reacted Si(001)-(2x1)-Surface — Niklas Fornefeld1, •Felicitas Scholz1, Francois Rochet3, Stefan Kubsky2, and Ulrich Köhler1 — 1AG Oberflächenphysik, Ruhr-Universität Bochum, Germany — 2Synchrotron Soleil, St. Aubin (Paris), France — 3Laboratoire de Chimie Physique Matière et Rayonnement, Univ. P. et M. Curie, Paris, France
Surface bound hydroxyl-groups on silicon surfaces became an interesting topic for research due to their use as interface between an anorganic and an organic semiconductor. To investigate the binding properties (e.g. pKa-value) on those silanol-groups we studied the adsorption of ammonia (NH3) as an example for a Lewis base. In order to verify the adsorption geometry and the behavior during the process of unfreezing, that had been proposed on the basis of XPS/NEXAFS studies, we studied the NH3/(H/OH)/Si(001)-(2x1) system with HREELS at 125 K and 300 K. We report the self-limited adsorption of molecular ammonia on surface silanols in a proton-acceptor geometry (NH3 giving lone pair to Si-OH) at 125 K. The saturation coverage was found to be smaller than one monolayer. In addition there were indications for the growth of a small amount of SiNH2 (dissociation of NH3) that seems to increase with higher dosage up to 17 L. At 300K (after unfreezing) the molecularly bound ammonia completely desorbs due to weak bonding while the behavior of SiNH2 could not finally be cleared up.