SurfaceScience21 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 33: Poster Session III: Semiconductor substrates I
O 33.5: Poster
Dienstag, 2. März 2021, 10:30–12:30, P
Temperature dependent adsorption of Trimethylamine (TMA) on water-functionalized Si(001)-(2x1) surfaces — •Niklas Fornefeld1, Lucia Pérez Ramírez2, François Rochet2, Stefan Kubsky3, and Ulrich Köhler1 — 1Experimentalphysik IV, Ruhr-Universität Bochum, Bochum, Germany — 2Laboratoire de Chimie Physique matière et Rayonnement, Univ. P. et M. Curie, Paris, France — 3Synchrotron Soleil, St. Aubin (Paris), France
Concerning functionalization of Si(001)-(2x1) with organic molecules, an intermediate water layer enables better control of the adsorption processes due to the reduction of possible adsorption sites. To investigate the binding properties on surface silanols (SiOH) and to examine the chemical reactivity we studied the vibrational modes of TMA in the temperature range between 100 K and 300 K during adsorption on a H2O/D2O reacted Si(001)-(2x1) surface using HREELS in comparison to XPS results. Both complementary techniques indicate that TMA adsorbs non-dissociatively to surface silanols forming acceptor H-bonds at T < 120 K and at T < 135 K under constant TMA flux. Self-limited TMA adsorption was found to occur already for T < 175 K affecting 80 % of the SiOH without the appearance of the characteristic ν(SiO-H) redshift for H-bonding seen at lower temperature. Both adsorption reactions are reversible processes involving TMA N lone pair electrons thus ruling out TMA protonation by either SiH or SiOH. Analyzation of the ν(CH3) Bohlmann band allows us to estimate the bond strength of adsorbed TMA to be in between dative and intermolecular bonding found in TMA mono-/multilayers on pristine Si(100).