Experimental setup for in situ and real-time spectroscopic ellipsometry and FTIR spectroscopy.
Investigated terminations (a) dimethylsilyl, (b) trimethylsilyl, and (c) alkylsilyl groups containing different numbers of methylene groups made from occtadecyldimethylchlorosilane, and (d) octadecylsilyl terminations prepared from octadecyltrichlorsilane [C8 and C18 SAMs].
Fitting error and test of the stability of the ellipsometer with time. The first point was taken as a reference to calculate the effective optical properties of the substrate. The model presented in the inset was used to fit the points. Since the surface was not terminated the thickness of the film characterized by the Cauchy dispersion model should be zero.
Experimentally measured ellipsometric angles (a) and (b) before (closed symbols) and after (open symbols) layer oxidation for ODS (squares) and DMS (circles). Zooms of some parts of the graphs are presented as insets. In some spectral regions the reference measurements did not coincide with previous measurements of the reference if the sample was removed between experiments (open triangles).
Differences between the measured ellipsometric angles before and after the oxidation process for alkylsilyl terminations. Squares represent experimentally measured points and solid lines indicate data simulated with a Cauchy dispersion model.
Changes of the layer thickness during laser-induced oxidation for the DMS termination, divided into stages I–VI.
(a) Change of the layer thickness measured for alkylsilyl chains with different numbers of methylene units during oxidation. (b) The effective thickness of alkylsilyl terminations vs number of methylene groups in the chain. The error bars indicate the statistical error. The line represents a linear fit, which yields an increment of per methylene group.
Decay of relative film thickness for several alkylsilyl terminations with a different number of units in logarithmic scale vs oxidation time. The rate coefficients were determined from the linear fits indicated in the figure.
Single-reflection FTIR spectra of hydrocarbon layers on oxide-covered silicon. Spectra recorded before the photoinduced oxidation were divided by spectra recorded after oxidation. (a) Several FTIR survey spectra are presented as measured; (b) FTIR spectra of alkylsilyl chains with different chain lengths . The spectra are shifted vertically for clarity. (c) FTIR spectra of TMS and DMS layers.
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