Dietrich P M, Streeck C, Glamsch S, Ehlert C, Lippitz A, Nutsch A, Kulak N, Beckhoff B, Unger W E S
Bundesanstalt für Materialforschung und -prüfung (BAM) , Unter den Eichen 87, 12205 Berlin, Germany.
Physikalisch-Technische Bundesanstalt (PTB) , Abbestr. 2-12, 10587 Berlin, Germany.
Anal Chem. 2015 Oct 6;87(19):10117-24. doi: 10.1021/acs.analchem.5b02846. Epub 2015 Sep 10.
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 nm(2) was calculated from the layer's nitrogen mass deposition per area unit obtained by reference-free TXRF. Complementary energy and angle-resolved XPS (ER/AR-XPS) 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.
有机硅烷通常用于使各种载体材料功能化以便进一步修饰。然而，关于成层后表面官能团密度的可靠定量信息却很少能获得。在此，我们展示了利用无参比全反射X射线荧光光谱（TXRF）和X射线光电子能谱（XPS）对天然氧化硅片上由含氮硅烷分子制成的有机纳米薄层进行的分析。根据通过无参比TXRF获得的每单位面积层的氮质量沉积量计算得出每纳米²有2 - 4个硅烷分子的面密度。利用Si 2p芯能级区域的互补能量和角分辨XPS（ER/AR - XPS）来分析有机（硅烷层） - 无机（硅片）界面的最外层区域。鉴定并定量了不同共存的硅物种，如硅、天然氧化硅和硅烷。作为所展示概念验证的结果，通过用无参比TXRF对XPS方法进行校准，获得了含氮硅烷作为内在标记的面密度的绝对且可溯源的值。此外，结果表明ER/AR - XPS有助于测定由除硅之外没有杂原子标记的硅烷制成的（单）层中的面密度。在用无参比TXRF校准后，当使用硅烷硅原子的XPS组分强度时，可以确定这些硅烷分子的面密度。
