Dresden 2017 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 50: Semiconductor Substrates: Structure, Epitaxy, Growth and Adsorption

O 50.5: Poster

Dienstag, 21. März 2017, 18:30–20:30, P1A

HREELS of Ammonia Adsorbed on a Water Reacted Si(001)-(2x1) Surface — •Niklas Fornefeld¹, Felicitas Scholz¹, Ulrich Köhler¹, Stefan Kubsky², and Francois Rochet³ — ¹Arbeitsgruppe 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 surface became an interesting topic for research due to the use as interface between an anorganic and an organic semiconductor. To investigate the binding properties on those silanol-groups we studied the adsorption of ammonia (NH₃) as an example for a Lewis base. In order to determine the adsorption kinetics and geometry and the behavior during the process of unfreezing, we studied the NH₃/(H/OH)/Si(001)-(2x1) system with High Resolution Electron Energy Loss Spectroscopy (HREELS) in the temperature range between 100K and 300K.

We report the self-limited adsorption of molecular ammonia on surface silanols in a proton-acceptor geometry (ammonia giving its lone pair to Si-OH) below 140K. Around 160K the molecularly adsorbed ammonia desorbs within seconds. Taking temperature dependent spectra, the desorption kinetics was quantitatively determined. In addition, there are indications for the growth of a small amount of dissociated ammonia on isolated dangling bonds of the water covered surface.