ac5b02846_si_001.pdf (1.16 MB)
Quantification of Silane Molecules on Oxidized Silicon: Are there Options for a Traceable and Absolute Determination?
journal contribution
posted on 2015-10-06, 00:00 authored by P. M. Dietrich, C. Streeck, S. Glamsch, C. Ehlert, A. Lippitz, A. Nutsch, N. Kulak, B. Beckhoff, W. E.
S. UngerOrganosilanes 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/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.