TY - JOUR A1 - Dietrich, Paul A1 - Streeck, C. A1 - Glamsch, Stephan A1 - Ehlert, Christopher A1 - Lippitz, Andreas A1 - Nutsch, A. A1 - Kulak, N. A1 - Beckhoff, B. A1 - Unger, Wolfgang T1 - Quantification of silane molecules on oxidized silicon: Are there options for a traceable and absolute determination? JF - Analytical chemistry N2 - Organosilanes are used routinely to functionalize various support materials for further modifications. Nevertheless, reliable quantitative information about surface functional group densities after layer formation is rarely available. Here, we present the analysis of thin organic nanolayers made from nitrogen containing silane molecules on naturally oxidized silicon wafers with reference-free total reflection X-ray fluorescence (TXRF) and X-ray photoelectron spectroscopy (XPS). An areic density of 2−4 silane molecules per nm2 was calculated from the layer’s nitrogen mass deposition per area unit obtained by reference-free TXRF. Complementary energy and angle-resolved XPS (ER/ARXPS) in the Si 2p core-level region was used to analyze the outermost surface region of the organic (silane layer)−inorganic (silicon wafer) interface. Different coexisting silicon species as silicon, native silicon oxide, and silane were identified and quantified. As a result of the presented proof-of-concept, absolute and traceable values for the areic density of silanes containing nitrogen as intrinsic marker are obtained by calibration of the XPS methods with reference-free TXRF. Furthermore, ER/AR-XPS is shown to facilitate the determination of areic densities in (mono)layers made from silanes having no heteroatomic marker other than silicon. After calibration with reference-free TXRF, these areic densities of silane molecules can be determined when using the XPS component intensity of the silane’s silicon atom. PY - 2015 DO - https://doi.org/10.1021/acs.analchem.5b02846 SN - 0003-2700 SN - 1520-6882 VL - 87 IS - 19 SP - 10117 EP - 10124 PB - American Chemical Society CY - Washington, DC AN - OPUS4-34796 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Ehlert, Christopher T1 - A Detailed Assignment of NEXAFS Resonances of Imidazolium Based Ionic Liquids T2 - Bessy User Meeting T2 - Bessy User Meeting CY - Berlin, Germany DA - 2015-12-10 PY - 2015 AN - OPUS4-35212 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Ehlert, Christopher T1 - Investigation of NEXAFS Resonances of Self-Assembled Monolayers by Transition Potential Density Functional Theory T2 - Bessy User Meeting T2 - Bessy User Meeting CY - Berlin, Germany DA - 2015-12-10 PY - 2015 AN - OPUS4-35213 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Ehlert, Christopher A1 - Kröner, D. A1 - Saalfrank, P. T1 - A combined quantum chemical/molecular dynamics study of X-rayphotoelectron spectra of polyvinyl alcohol using oligomer models JF - Journal of Electron Spectroscopy and Related Phenomena N2 - X-ray photoelectron spectroscopy (XPS) is a powerful tool for probing the local chemical environment ofatoms near surfaces. When applied to soft matter, such as polymers, XPS spectra are frequently shifted andbroadened due to thermal atom motion and by interchain interactions. We present a combined quantummechanical QM/molecular dynamics (MD) simulation of X-ray photoelectron spectra of polyvinyl alcohol(PVA) using oligomer models in order to account for and quantify these effects on the XPS (C1s) signal. Inour study, molecular dynamics at finite temperature were performed with a classical forcefield and by abinitio MD (AIMD) using the Car–Parrinello method. Snapshots along the trajectories represent possibleconformers and/or neighbouring environments, with different C1s ionization potentials for individualC atoms leading to broadened XPS peaks. The latter are determined by Δ-Kohn Sham calculations. Wealso examine the experimental practice of gauging XPS (C1s) signals of alkylic C-atoms in C-containingpolymers to the C1s signal of polyethylene. We find that (i) the experimental XPS (C1s) spectra of PVA (position and width) can be roughly repre-sented by single-strand models, (ii) interchain interactions lead to red-shifts of the XPS peaks by about0.6 eV, and (iii) AIMD simulations match the findings from classical MD semi-quantitatively. Further, (iv)the gauging procedure of XPS (C1s) signals to the values of PE, introduces errors of about 0.5 eV. KW - XPS KW - Quantummechanical molecular dynamics simulation KW - Polyvinyl alcohol PY - 2015 DO - https://doi.org/10.1016/j.elspec.2014.12.007 SN - 0368-2048 VL - 199 SP - 38 EP - 45 PB - Elsevier B.V. AN - OPUS4-39290 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -