Characterization of surfaces of various polymers by electron spectroscopy

Cataloged from PDF version of article.X-ray induced photo and Auger electron spectroscopic techniques have been used to characterize the surface composition of biaxially oriented polypropylene sheets with and without corona discharge treatment. The surfaces of polypropylene sheets without corona treatment contain very small amounts of 0 and the C 1 s peak is narrow, consisting mainly of -CH groups and less than 5% -C-O groups. After corona treatment the intensity of the 01s peak increases by a factor of 8, the Cls peak broadens and -C-O intensity increases by a factor of 3. The surfaces of aluminized polypropylene contains both aluminium oxide and metallic aluminium. From the measured intensity ratio of the A13’/A10 peaks the thickness of the oxide layer is estimated to be smaller than 4 nm. Aging increases the carbon content of the surface without changing the aluminium oxide/ metal composition. 0 1997 Elsevier Science B.V

XPS investigation of Si-diode in operation

Cataloged from PDF version of article.X-ray photoelectron spectroscopy (XPS) is utilized to investigate a Si-diode during its operation under both forward and reverse bias. The technique traces chemical and location specified surface potential variations as shifts of the peak positions with respect to the magnitude as well as the polarity of the applied voltage bias, which enables one to separate the dopant dependent shifts from those of the chemical ones

Communication: Enhancement of dopant dependent x-ray photoelectron spectroscopy peak shifts of Si by surface photovoltage

Cataloged from PDF version of article.Binding energies measured by x-ray photoelectron spectroscopy (XPS) are influenced by doping, since electrons are transferred to (p-type) and from (n-type) samples when they are introduced into the spectrometer, or brought into contact with each other (p-n junction). We show that the barely measurable Si2p binding energy difference between moderately doped n- and p-Si samples can be enhanced by photoillumination, due to reduction in surface band-bending, which otherwise screens this difference. Similar effects are also measured for samples containing oxide layers, since the band-bending at the buried oxide-Si interfaces is manifest as photovoltage shifts, although XPS does not probe the interface directly. The corresponding shift for the oxide layer of the p-Si is almost twice that of without the oxide, whereas no measurable shifts are observable for the oxide of the n-Si. These results are all related to band-bending effects and are vital in design and performance of photovoltaics and other related systems. (C) 2011 American Institute of Physics

Probing Voltage Drop Variations in Graphene with Photoelectron Spectrosopy

Cataloged from PDF version of article.We use X-ray photoelectron spectroscopy (XPS) for characterization of voltage drop variations of large area single-layer graphene on quartz substrates, by application of a voltage bias across two gold electrodes deposited on top. By monitoring the spatial variation of the kinetic energies of emitted Cls photoelectrons, we extract voltage variations in the graphene layer in a chemically specific format. The potential drop is uniform across the entire layer in the pristine sample but is not uniform in the oxidized one, due to cracks and/or morphological defects created during the oxidation process. This new way of data gathering reintroduces XPS as a major analytical tool for extracting electrical as well as chemical information about surface and/or nanostructured materials

XPS for chemical- and charge-sensitive analyses

Cataloged from PDF version of article.By recording X-ray photoelectron spectroscopic binding energy shifts, while subjecting samples to a variety of optical and electrical stimuli, information about charge accumulation on materials or surface structures can be obtained. These stimuli included d.c. as well as a.c. electrical and/or optical pulses covering a wide frequency range (10−3 to 106 Hz) for probing charging and/or photovoltage shifts, stemming from impurities, dopants, defects, etc., whether created intentionally or not. The methodology is simple to implement and provides several new dimensions for thin films and materials analyses

Dynamic XPS measurements of ultrathin polyelectrolyte films containing antibacterial Ag–Cu nanoparticles

Cataloged from PDF version of article.Ultrathin films consisting of polyelectrolyte layers prepared by layer-by-layer deposition technique and containing also Ag and Cu nanoparticles exhibit superior antibacterial activity toward Escherichia coli. These films have been investigated with XPS measurements under square wave excitation at two different frequencies, in order to further our understanding about the chemical/physical nature of the nanoparticles. Dubbed as dynamical XPS, such measurements bring out similarities and differences among the surface structures by correlating the binding energy shifts of the corresponding XPS peaks. Accordingly, it is observed that the Cu2p, Ag3d of the metal nanoparticles, and S2p of cysteine, the stabilizer and the capping agent, exhibit similar shifts. On the other hand, the C1s, N1s, and S2p peaks of the polyelectrolyte layers shift differently. This finding leads us the claim that the Ag and Cu atoms are in a nanoalloy structure, capped with cystein, as opposed to phase separated entities. VC 2014 American Vacuum Society

Electrooxidation of methanol on doped polypyrrole films in acidic media

Cataloged from PDF version of article.Electrooxidation of methanol was realised on platinum and perchlorate anion doped polypyrrole film electrodes in acidic media. A systematic kinetic investigation was performed and optimum experimental conditions for the preparation of the electrocatalytic system were determined. The presence of ClO4- anions was confirmed by XPS analysis of the doped polymer matrix. (C) 2001 Elsevier Science B.V. All rights reserved

Practitioners Evaluation On The Procedural Aspects Of An English Language Portfolio

This study aims to share English language practitioners' reflections on the adaptation of teaching methods and materials during the pre-validation period of the European Language Portfolio (ELP). In order to achieve this aim, a high school was selected as the scope of research, since it has started to adapt the English language teaching curriculum, syllabuses, instruction methods and assessment in line with the Common European Framework for the teaching of English as a foreign language for the last 4 years. A focus group of eight teachers was selected to collect data via semi-structured interviews. During the data collection procedure, the participants evaluated the process and procedures in terms of the related themes of SWOT analysis. The collected data was analyzed through coding and theme identification

The compressibility of high purity YbB2

Cataloged from PDF version of article.The compressibility and phase stability of YbB2 are investigated under high pressure using high-resolution synchrotron x-ray diffraction in a diamond anvil cell. The bulk modules of high purity YbB2 is obtained as similar to 182 GPa using the Birch-Murnaghan equation of state. The patterns measured up to 20 GPa and the pressure dependence of normalized lattice parameters, a/a(0) and c/c(0), reveal that the compressibility of YbB2 is low and fairly isotropic, and this material can be classified as a hard material. X-ray photoemission studies demonstrate that Yb in YbB2 has a mostly trivalent valence state at room temperature. Moreover, sample preparation details provide a new insight into the high purity synthesis of YbB2 at ambient pressure and moderate temperatures. The presented structural and compressibility results are in agreement with the available theoretical and experimental data on binary rare-earth borides and can serve as a reliable reference for future studies

Platinum-palladium loaded polypyrrole film electrodes for the electrooxidation of D-glucose in neutral media

Cataloged from PDF version of article.Modified polymer films with metal particles incorporated into the films by electrodeposition are known as possible electrocatalysts for various electrode reactions such as fuel cell applications. This work presents some results concerning the electrooxidation of D-glucose at modified polymer film electrodes prepared on a platinum substrate. This reaction has a great deal of interest in view of its applications to detection systems (glucose sensor), fuel cells (pacemakers) and electroorganic systhesis. The modified polymer film electrodes contain platinum and/or palladium particles dispersed in the polypyrrole film by electrodeposition in neutral media. Addition of palladium to platinum modifies the electrocatalytic behaviour of the electrode drastically. The modification is thought to involve minimisation of the poisoning of the catalyst, hence increasing its electrode activity. © 1999 Elsevier Science S.A. All rights reserved