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- ESCA (14) (entfernen)
Chemical derivatization XPS is used for the quantitative determination of amines at conventional organic surfaces, and it is also applied to plasma-processed aminated surfaces. When using TFBA and PFB as derivatization reagents for tagging primary amino groups, unexpected fluorine species were observed in the second case. The existence of reaction pathways other than those expected for amine derivatization with PFB or TFBA has to be assumed. This phenomenon is tentatively interpreted as the result of C—F bond cleavage during derivatization reactions of TFBA and PFB at plasma-polymerized allylamine and other plasma-processed aminated surfaces. As a consequence, quantification procedures based on derivatization by PFB or TFBA will underestimate amine surface concentrations.
Ageing studies of plasma deposited organic films by surface chemical analysis (ESCA, ToF-SIMS, XAS)
(2007)
Overlayers of SiO2 (nominally 4, 6 and 8 nm thick) on silicon, prepared by thermal oxidation, were investigated using x-ray photoelectron spectroscopy (XPS). The thickness of these overlayers was obtained from a measurement of the photoelectron intensities originating from the substrate and the oxide overlayer by applying an appropriate quantitative model. The uncertainty budget of that thickness measurement method is given. The relative combined standard uncertainty of the method was found to be 15%. The effective attenuation lengths or the corresponding electron inelastic mean free paths are of considerable importance for both the estimated values of overlayer thickness and combined standard uncertainties. The XPS results were compared with ellipsometry data.
First results of an inter-laboratory comparison (27 participants in Europe, Japan and USA) of XPS data obtained with non-conducting samples are presented. Binding energies of Al 2s for alumina, N 1s and imide C 1s for Kapton and Sr 3p3/2 for a strontium titanate film on glass were obtained after static charge referencing with the help of 15 nm gold particles deposited at the surface of the test samples. For the alumina sample C 1s static charge referenced data are also presented. Repeat standard deviations (sr), between standard deviations (sb), reproducibility standard deviations (sR) and total means are evaluated from the experimental data. It can be stated that although the repeat standard deviation is as small as 0.05 eV in the best case, the standard deviation characterizing the reproducibility of the method is obviously not better than 0.15 eV in the best case at the present time. The knowledge of these standard deviations is important for metrology, validations of analytical procedures relying on qualitative photoelectron spectroscopy and XPS databanking.
Catalyst characterization
(2009)
Es wird gezeigt, dass mit einer Kombination der Oberflächenanalyseverfahren ESCA, ToF- SIMS und XAS eine erfolgreiche chemische Charakterisierung von Plasmapolymerfilmen erreicht werden kann. Es werden Elemente und Bindungstypen identifiziert und (semi-)quantitativ bestimmt. Eine Korrelation zwischen Abscheidebedingungen und chemischen Eigenschaften der Plasmapolymerschichten kann hergestellt werden; eine kontrollierte Abscheidung wird damit möglich. Alterungsprozesse, die als Folge einer Atmosphärenexposition auftreten, können beobachtet werden. Die direkte Verbindung der Analysetechniken mit einem Plasmareaktor ermöglicht es, die Alterungsphänomene der Schichten systematisch mit Bezug auf eine frisch abgeschiedene und keinerlei Atomsphäre ausgesetzte Plasmapolymerschicht zu studieren.
Die Verfahrensweise wird exemplarisch am Beispiel von Ethylen-, Allylamin- und Allylalkohol-Plasmapolymerschichten demonstriert.
A survey is given on how a combination of modern methods of surface analysis with appropriate data evaluation procedures can be used to provide a thorough chemical characterization of plasma polymerized organic films often called plasma polymers. Technologically relevant parameters can be monitored versus variation of plasma process parameters and during ageing of the films on air. The level of development of analytical approaches reached during the last ten years opens many options which are useful to be applied in plasma process development, optimization and control. However, in a number of important cases further development of analytical methods is required. Another future challenge is to develop standards with metrological underpinning to reach comparability of measurements in the community.
Translated Abstract
Chemische Oberflächencharakterisierung von Plasmapolymerschichten: Was leisten die Messverfahren heute?
Es wird ein Überblick gegeben, wie mit dem kombinierten Einsatz moderner Methoden der Oberflächenanalytik und fortgeschrittener Datenreduktionsverfahren eine umfassende chemische Charakterisierung von plasmachemisch abgeschiedenen organischen Schichten, oft als Plasmapolymere bezeichnet, erreicht werden kann. Die chemischen Eigenschaften sind bestimmend für wichtige technologische Parameter der Schichten und können sowohl durch Plasmaprozessparameter als auch von der Liegezeit bestimmt werden. Eine Standardisierung von Prozeduren der Oberflächenanalytik zur Charakterisierung von Plasmapolymeren und ihre metrologische Begründung sind Schwerpunkte in der weiteren Entwicklung.
Plasma deposited ethylene/allylamine and styrene/allylamine copolymer films were prepared and analyzed using XPS, NEXAFS and ToF-SIMS. The relative partial flow rate of the each monomer was used as the variable deposition parameter, while the other deposition parameters were kept constant at optimized values for the retention of functional groups. The effect of the variation in the relative partial flow rates of co-monomers on various chemical aspects of the films like unsaturation, nitrogen retention and branching was investigated revealing several non-linear correlations. This observation is taken as an indication for chemical copolymerization processes during film deposition. An attempt is made to compare these non-linear correlations with approaches which have been developed for classic radical copolymerization processes. The aging behavior of these plasma copolymer films was also studied; the results indicated a stabilization against oxidation in comparison to the aging of allylamine plasma homopolymers.