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Eingeladener Vortrag
- nein (120)
NEXAFS analysis of a plasma treated, partially crystalline poly(ehtylene terephtalate) surface
(1996)
Elastomeric sealants may contain organic silicon compounds. The use of these sealants for housings for electronic components is harmful for the reliability of electric contacts inside. In order to prevent electronic components from malfunction, quality control of elastomeric sealants is required. An analytical procedure developed to fulfil this requirement was developed. It is based on electron spectroscopy for chemical analysis (ESCA). Information on the silicon compounds existing at the surface of elastomeric sealants is provided by this method. Silicon in organic and inorganic compounds can be differentiated with the help of Si 2p photoelectron spectra. Quantitative results can be obtained too. The uncertainty budget of the quantitative procedure is estimated.
Results of the inter-laboratory comparison "Determination of nanometric step heights with AFM"
(2002)
Non-destructive chemical depth-profiling of plasma polymers by variable excitation energy XPS
(2003)
Self-assembled octadecyltrichlorosilane (CH3(CH2)17SiCl3, OTS) films were deposited on an oxidized silicon wafer. They were carefully exposed to a low-pressure oxygen direct current (dc) plasma and/or Cr vapor. Subsequently, they were characterized by X-ray photoelectron spectroscopy, near-edge X-ray absorption fine structure spectroscopy, and atomic force microscopy. Detailed information on the oxygen functionalization and the molecular conformation of the OTS films was obtained. The main result was that functionalization conditions can be found where the order of the film remains almost unaffected. Similarly, Cr evaporation of pure OTS films revealed only slight effects on the order in the film. Cr evaporation of an ordered but functionalized OTS film immediately changes its state toward a fully isotropic one. In the course of interaction, oxygen sites at the surface of the functionalized OTS film are reduced whereas Cr becomes oxidized. A redox reaction scheme is proposed for this interfacial reaction. Finally, it is concluded that the given study should be of importance for advanced plasma processing of polyolefins.
Organic thin films with defined chemical structures and physical properties are required for various applications. Plasma polymerization is of technological interest, since the deposition of plasma polymers is possible on any material of any shape in the desired thickness. We report on the TOF-SIMS (TOF: time-of-flight) and XPS investigations of pulse plasma poly(acetylene) and alkali metal doped pulse plasma poly(acetylene) films. The combination of TOF-SIMS and XPS supplies detailed information on the surface chemistry of these films. Application of both methods provides the possibility for cross-checking certain results. Moreover the different sensitivities of the methods can be utilized. According to the TOF-SIMS and XPS data it can be concluded that the interaction of alkali metals with plasma poly(acetylene) results in electrovalent bonds of the type Me?+C?- between carbon and metal. Furthermore carbonoxygenmetal interactions were observed. These interactions are of the type C=O?-cdots, three dots, centeredMe?+ and/or CO?-Me?+.
Zusammenfassung
Some methods of nano-scale analysis are on the threshold of being a standard method in industry and therefore quality assurance becomes important. But, at the present time, there are deficits in standardisation and validation of these methods. Therefore, we have organised method comparisons and interlaboratory comparisons to overcome these deficits. We report the results of an interlaboratory comparison in step-height determination by atomic force microscopy and the development of a reference material for laterally resolving methods of material analysis.
Pure and PDMS contaminated PS oligomers films were investigated both by time-of-flight static secondary ion mass spectrometry (TOF-SSIMS) and X-ray photoelectron spectroscopy (XPS).
The secondary ion spectra from the PDMS contaminated PS oligomers were almost completely related to PDMS. XPS revealed a PDMS contamination characterized by a silicon surface concentration of 6 at.%. Obviously siloxane contaminants existing on the surface of a silicon wafer may diffuse towards the PS oligomers outermost surface resulting in a rather high PDMS surface concentration of about 85%. Due to the known differences in the information depth and sensitivity of SSIMS and XPS very different detection limits are to be considered.
In elimination of siloxane contaminants by ultrasonication in hexane was found to be an effective way. Another common organic cleaning procedure, which is ultrasonication in trichloroethylene (TCE), subsequently in isopropanol and finally in acetone was found to be ineffective for cleaning of PDMS contaminated silicon wafers.
Barrier properties of plasma and chemically fluorinated polypropylene and polyethyleneterephthalate
(1995)
The functionalization, perfluorination or an coating of polypropylene (PP) and polyethyleneterephthalate (PET) surfaces in different plasma atmospheres and in an F[2] + N[2] gas mixture were investigated. The aim of this work was to form a barrier layer against solvent and fuel permeation. Typical test solvents were n-pentane, toluene, tetrachloroethylene and mixtures of n-pentane and methanol. The permeation was gravimetrically measured. The permeation of the solvent mixtures was analyzed by mass spectrometry and Fourier transform IR spectroscopy. The permeation of the solvent mixtures through the plasma-modified polymer samples was associated with increased absorption of polar solvent components in the polymer film. The thickness of the plasma-fluorinated PP surface layer was 10-100 nm and that of chemically fluorinated PP about 5000 nm. Nearly the same barrier efficiency was measured for both plasma- and chemically fluorinated samples.
Neues vom Urkilogramm
(1999)
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.
Results of an interlaboratory comparison of XPS data obtained with stainless steel are presented. Only one photoelectron spectrometer model was used. The stainless-steel sample surfaces were analysed in different states by XPS: as received, after sputtering to I(C 1s)/I(Fe 2p3/2) 0.025 and after removing a chromium-enriched oxide layer following a certain protocol. The Fe, Cr and Ni elemental concentrations were evaluated from the respective XPS data submitted by the participants of the interlaboratory test experiment. Total means, repeat standard deviations (sr) and reproducibility standard deviations (sR) are presented. The best reproducibility standard deviations were obtained for the XPS analysis after removal of a chromium-enriched oxide layer and quantification of the XPS intensities without taking the contamination elements of carbon and oxygen into account. The absolute reproducibility standard deviation of the elemental concentrations in that case is as small as 1.1-1.5 at.%. This gives 2%, 6% and 16% for the relative reproducibility standard deviation of the concentrations of iron, chromium and nickel, respectively. The total means of the iron, chromium and nickel concentrations finally obtained agree within 2sR with bulk values determined by wavelength-dispersive x-ray fluorescence spectroscopy. Comparison to an earlier interlaboratory test experiment shows that using only one model of photoelectron spectrometer reduces the reproducibility standard deviations efficiently. Copyright © 2002 John Wiley & Sons, Ltd.
Die offenporige Struktur des Holzes und dessen chemische Zusammensetzung bieten sich an, über Tränkverfahren geeignete Precursoren so an den inneren Oberflächen des Holzes zu fixieren, dass bei anschließender thermischer Behandlung ein umweltfreundlicher anorganisch-organischer Verbundwerkstoff entsteht. Aus der Literatur sind hierzu verschiedene Ansätze bekannt. - Ziel der vorliegenden Arbeit sind Verbesserungen der biologischen Beständigkeit, der Feuchtebeständigkeit unter Beibehaltung bzw. leichter Verbesserung der mechanischen Eigenschaften des Holzes. Dies wird durch eine chemische Verbindung (Haftung) zwischen den verbundbildenden Phasen Holz und Precursor und eventuell zusätzlichen Einbau von funktionellen organischen Gruppen realisiert. Als Precursoren dienen über den Sol-Gel Weg hergestellte Kieselsole, die nach vollständiger thermischer Umsetzung zu rein anorganischen Phasen (SiO2) führen. Die Sol-Gel Synthese konnte so optimiert werden, dass durch die Behandlung eine homogene Beschichtung aller Oberflächen erreicht werden kann.
Powder x-ray diffraction (XRD) defined -Al2O3 has been investigated by x-ray photoelectron spectroscopy (XPS) and x-ray excited Auger electron spectroscopy (XAES). The Au 4f7/2 orbital is used for static charge referencing. This feature originates from well-defined and chemically inert 20 nm highly dispersed gold particles deposited on the sample surface. The particles, with a narrow particle size distribution, were obtained from a highly purified colloidal solution (sodium concentration below 1 mg/l). This procedure allows a determination of gold-referenced XPS and XAES data sets. ©2001 American Vacuum Society.
Several approaches were investigated to produce monosort functionalized polymer surfaces with a high density and homogeneity of functional groups: (i) Plasma oxidation followed by wet-chemical reduction, (ii) formation of radicals and grafting on of functional group carrying molecules, (iii) plasma bromination followed by (iv) Williamson or Gabriel-like synthesis of spacer molecules, and (v) a pulsed plasma polymerization of functional groups bearing monomers or (vi) their copolymerisation with other comonomers. The formation of hydroxyl (OH), primary amino (NH2), and carboxyl (COOH) groups was studied in detail. The oxygen plasma treatment (i) in a low-pressure non-isothermal glow discharge results in the formation of a wide variety of O functional groups, polymer degradation and crosslinking. Low power densities and short exposure times (0.1 to 2 s) are required to functionalize a surface while preserving the original polymer structure. Carbonate, ester, and aromatic groups are rapidly degraded by an oxygen plasma treatment leading to scissions of polymer backbones and loss in molecular weight. Also the formation of macrocycles and C=C bonds was observed in a region of around 4 nm in depth. The investigated polymers could be classified by their degradation behaviour on exposure to the oxygen plasma.___TAGSTART___BR___TAGEND___ In order to maximize the process selectivity for OH groups, the variety of oxygen functionalities formed by the oxygen plasma was wet-chemically reduced by diborane, vitridetrade (Na complex), and LiAlH4. Typical yields were 9 to 14 OH groups per 100 carbon atoms.___TAGSTART___BR___TAGEND___ Plasma bromination (iii) (40 Br per 100 C atoms) of polymers, followed by grafting of spacer molecules (iv), has been proved to be a highly selective reaction.___TAGSTART___BR___TAGEND___ Another way to produce high densities of monosort functionalities was the pulsed plasma polymerization of functional group bearing monomers such as allylamine, allylalcohol or acrylic acid (v). The retention of chemical structure and functional groups during plasma polymerization was achieved by using low power densities and the pulsed plasma technique. The maximum yields were 30 OH, 18 NH2, and 24 COOH groups per 100 C atoms. To vary the density of functional groups a chemical copolymerization with ''chain-extending'' comonomers such as butadiene and ethylene was initiated in the pulsed plasma (vi). Additionally, the often-observed post-plasma oxidations of such layers initiated by reaction of trapped radicals with oxygen from the air were successfully suppressed by using NO gas as radical quencher.
This new functionalization method consists of the deposition of very thin plasma polymer layers (20 to 100 nm) of functional group bearing monomers in pulsed plasma. With allylalcohol, a maximum of 30 OH groups per 100 C atoms was measured with a selectivity of about 90% and a significant stability at long-time exposure to air. Allylamine was used to produce primary amino groups, with a maximum of 18 NH2 groups per 100 C atoms. Side reactions were observed during the storage in air, such as oxidation of the amino groups. Carboxylic groups could be produced using acrylic acid with a maximum concentration of 24 COOH groups per 100 C atoms. The most prominent side reaction was the decarbonylation/ decarboxylation of the acid group during plasma deposition.___TAGSTART___BR___TAGEND___ The variation of the density of functional groups using the pulsed-plasma polymerization of functional-group-bearing monomers was possible by the chemically-initiated radical copolymerization with either a chain-extending monomer, such as ethylene, or a cross linker, such as butadiene, in plasma. The density of functional groups could be adjusted continuously (0 to 30 OH, 0 to 18 NH2 and 0 to 24 COOH groups per 100 C atoms).___TAGSTART___BR___TAGEND___ The successful application of these densely functionalized polymer surfaces for producing biocompatible surfaces and for use in metalpolymer composites is proposed.