Quantification of silane molecules on oxidized silicon: are there options for a traceable and absolute determination?
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.
Bundesanstalt für Materialforschung und -prüfung (BAM) , Unter den Eichen 87, 12205 Berlin, Germany.
P M
PM
Dietrich
Physikalisch-Technische Bundesanstalt (PTB) , Abbestr. 2-12, 10587 Berlin, Germany.
C
C
Streeck
Bundesanstalt für Materialforschung und -prüfung (BAM) , Unter den Eichen 87, 12205 Berlin, Germany.|Institut für Chemie und Biochemie, Freie Universität Berlin , Fabeckstr. 34/36, 14195 Berlin, Germany.
S
S
Glamsch
Bundesanstalt für Materialforschung und -prüfung (BAM) , Unter den Eichen 87, 12205 Berlin, Germany.|Institut für Chemie, Universität Potsdam , Karl-Liebknecht-Straße 24-25, 14476 Potsdam, Germany.
C
C
Ehlert
Bundesanstalt für Materialforschung und -prüfung (BAM) , Unter den Eichen 87, 12205 Berlin, Germany.
A
A
Lippitz
Physikalisch-Technische Bundesanstalt (PTB) , Abbestr. 2-12, 10587 Berlin, Germany.
A
A
Nutsch
Institut für Chemie und Biochemie, Freie Universität Berlin , Fabeckstr. 34/36, 14195 Berlin, Germany.
N
N
Kulak
Physikalisch-Technische Bundesanstalt (PTB) , Abbestr. 2-12, 10587 Berlin, Germany.
B
B
Beckhoff
Bundesanstalt für Materialforschung und -prüfung (BAM) , Unter den Eichen 87, 12205 Berlin, Germany.
W E S
WE
Unger