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[en] Highlights: • The need by industry for small area analysis spurred the advent of the XPS Microprobe. • The Microprobe design allows for rapid x-ray induced secondary electron imaging. • Small areas of interest can quickly be located and analyzed. • Industrial applications include varied types of failure and contamination analyses. • Multipoint depth profiles can be obtained in one acquisition with one sputter crater. - Abstract: We will review the evolution of x-ray photoelectron spectroscopy (XPS / ESCA) instrumentation and applications that led to the development of the scanning XPS microprobe, describe its unique capabilities, and how they have impacted the use of XPS for industrial applications.
[en] Highlights: • Pyridine- and terpyridine terminated monolayers show different deposition qualities. • Distinction of different nitrogens by spectroscopic methods. • Monolayer qualities have a significant effect on layer-by-layer deposition. • When present, oxidization only occurs prior to monolayer deposition. • Preferential orientation in multilayers on one specific monolayer. - Abstract: The chemical composition of surfaces functionalized with self-assembled monolayers (SAMs) is an important parameter that determines their performance in a broad range of applications, from immobilizing molecular machines to initiation and growth control of MOFs (Metal-Organic Frameworks). In this article, a critical survey of XPS (X-ray photoelectron spectroscopy) and NEXAFS (near edge X-ray absorption fine structure) spectroscopy data for pyridine-functionalized monolayers on gold surfaces is presented to compile correlations that have been indiscernible before. Monolayers with aromatic backbones are compared to monolayers with aliphatic backbones. Monolayers with pyridine end-groups are compared to mixed monolayers formed terpyridine-functionalized by molecules end-groups and non-functionalized molecules. Thiol-oxidation during ageing of the SAMs in air is addressed. And finally, the addressability of the SAMs for the deposition of metal-ions and organic molecules is investigated and compared. This work consequently delivers a comprehensive set of spectroscopic data of (ter-)pyridine-terminated SAMs and their performance as template for the preparation of functional multilayers of macrocycles exhibiting a preferential orientation.
[en] In high-temperature superconductors with a layered crystal structure out-of-plane contributions are often neglected, while the copper-oxygen planes are commonly considered to dominate the electronic properties around the Fermi energy. Here we report on a resonant photoemission study of (Pb,Bi)2201 and (Pb,Bi)2212 single crystals to unravel the resonant decay mechanisms at the Cu 2p absorption edge. We demonstrate a pronounced polarization dependence caused by two different Auger processes for in-plane and out-of-plane orientations. We deduce that the lowest energy valence state being involved in the two Auger processes, consists of three-dimensional contributions by admixed out-of-plane Sr, Bi, and O 2p states. It also suggests that the doping-induced charge density is dynamic, fluctuating within the Cu-O plane, and spills out perpendicular to it.
[en] Chitosan with its surface-properties and biodegradability is a promising biomaterial for green packaging applications. Till now, this application is still limited due to chitosan high sensitivity to water. Some existing studies deal with the incorporation of hydrophobic additives to enhance water-proof performances of chitosan films. As these additives may impair the film properties, our study focuses on chitosan efficient hydrophobization by means of simple and successful surface grafting reactions. Chitosan films prepared by solvent casting were modified by means of surface-initiated activators regenerated by electron transfer atom radical polymerization (SI-ARGET-ATRP) of 2-hydroxyethyl methacrylate (HEMA) followed by esterification reaction with fluorinated acyl compound. X-ray photoelectron spectroscopy (XPS), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and Time-of-Flight Secondary Ion Mass Spectroscopy (ToF-SIMS) highlighted the surface chemical changes after each step. Surface properties were investigated by contact angle measurements and surface energy calculations. Hydrophobic surfaces with low surface energy and good water-repellent properties were obtained using a simple handling polymerization procedure. This is the first study in applying ARGET ATRP to prepare hydrophobic biopolymer films offering potential applications in packaging. (author)
[en] Highlights: • Several applications of using XPS in an industrial laboratory that supports manufacturing and R&D activities are discussed. • Common approaches by XPS to surface chemical analytical problems are discussed. • Problems such as contamination, characterization of thin films, and determination of surface chemistry are presented. - Abstract: X-ray photoelectron Spectroscopy (XPS) is a widely-used technique for surface chemical analysis. In an industrial laboratory XPS can be used for a wide variety of applications ranging from identification of contamination on a surface to characterization of materials as process control, or as a method for characterizing new materials in a research environment. Some analyses are performed to provide a ‘yes’ or ‘no’ answer to questions such as ‘is silicone present?’ or ‘was the surface plasma treated?’. In other cases, qualitative analysis or a simple approach for quantification does not adequately describe a material. A more detailed analysis may require imaging or depth profiling, and the use of numerical methods such as curve fitting, overlayer modeling, or linear least squares fitting to more accurately describe a material. We relate selected vignettes where XPS spectral analysis, imaging, and sputter profiling are applied to some of the many types of samples that have come into our industrial laboratory.
[en] Full text: Aluminum and its alloys consist of an important category of materials due to its abundance and easy handling which gives them a high technological value. However, they are reactive and susceptible to corrosion in wet and saline environments, because under these conditions the oxide layer can be penetrated by the corrosive medium . Studies have been developed as efforts to introduce environmentally correct treatments capable of improving the anti corrosive performance of these materials . It is presented here the study of a new surface treatment for the AA2024-T3 aluminum alloy that involves the production of a superhydrophobic surface capable of hindering the access of the electrolyte to the metallic surface. The corrosion behavior of Trimethoxy(propyl)silane treated AA2024-T3 aluminum alloy was evaluated by subjecting the sample to different pre-treatments. Samples were characterized by optical profilometry, Water Contact Angle (WCA) and X-ray photoelectron spectroscopy (XPS). Superhydrophobic AA2024-T3 aluminum alloy showed static WCA equal to 157º with contact angle hysteresis lower than 10 degrees. The evaluation of the corrosive behavior was performed in a Gamry Interface 1000 potentiostat in a 0.05 mol L-1 NaCl solution. Electrochemical Impedance Spectroscopy analysis showed higher impedance value for the superhydrophobic AA2024-T3 aluminum alloy among all the treatments studied. This best anti corrosive performance for the superhydrophobic AA2024-T3 was confirmed by the lowest current density and higher corrosion potential obtained by potentiodynamic polarization measurements. Scanning Electron Microscopy characterization of the material is under way.References:  Buchheit, R. G.; Grant, R. P.; Hlava, P. F.; Mckenzie, B.; Zender, G. L.; J. Electrochem. Soc., 144, 2621 (1997).  Dalmoro, V.; dos Santos, J.H.Z.; Armelin, E.; Alemán, C.; Azambuja, D.S.; Corros. Sci., 60, 173 (2012). (author)
[en] Highlights: • Automated as-is analysis of insulating samples utilizing standalone NAP XPS system. • Environmental Charge Compensation for charge neutralization in NAP XPS. • NAP XPS intrinsic charge compensation on polymers and commercial products. - Abstract: X-ray photoelectron spectroscopy (XPS) has become a routine analysis method to determine the chemical composition and bonding states of elements of sample surfaces in many industrial applications, like materials development, failure analysis, quality control and device certification. To obtain significant results the analyses of such samples require a fast analysis with reliable quantification and stable data for repeated experiments. In standard XPS experiments under ultrahigh vacuum (UHV) conditions the significance of the results can be affected by changing surface compositions under the analysis conditions, different degrees of degassing and thus changing degrees of differential charging in insulating samples. In this publication the positive influence of XPS analysis under elevated pressures, often named Near-Ambient Pressure XPS or “Environmental XPS” is shown for different samples. Furthermore the process of charge compensation in gas pressures of 1–2 mbar is introduced, followed by a discussion of the perspectives of this “Environmental Charge Compensation”. The paper discusses the efficiency and stability of Environmental Charge Compensations for typical insulating test samples, as well as for different bulk insulators. The additional capability of XPS in elevated pressures is demonstrated on a superabsorbent polymer typically used in diapers, showing the difference of the analysis results for its wet and dry state. The paper ends with the example of a commercial printed circuit board demonstrating the power of the method for routine analysis of complete devices.
[en] Comprehensive computer simulations of the Alfvén eigenmode burst, which is the synchronized sudden growth of multiple Alfvén eigenmodes (AEs) interacting with energetic particles, were conducted with continuous neutral beam injection, collisions, and particle losses. It is found that the energetic-particle distribution in phase space reaches a ‘critical distribution’ with a stairway structure where a resonance overlap triggers the Alfvén eigenmode burst. Before the burst, the gradual growth of the AEs associated with the beam injection broadens the resonant regions in phase space forming the distribution into a stairway shape. When the distribution reaches the ‘critical distribution,’ a resonance overlap triggers multiple resonance overlaps leading to the synchronized growth of AEs and the collapse of the distribution. For another run with the beam deposition power reduced to one-half, the energetic-particle distribution function just before the Alfvén eigenmode burst is close to that for the original beam power. This result indicates that the critical distribution for the Alfvén eigenmode burst is present. (paper)
[en] Cluster science as a bridge linking atomic molecular physics and condensed matter inspired the nanomaterials development in the past decades, ranging from the single-atom catalysis to ligand-protected noble metal clusters. The corresponding studies not only have been restricted to the search for the geometrical structures of clusters, but also have promoted the development of cluster-assembled materials as the building blocks. The CALYPSO cluster prediction method combined with other computational techniques have significantly stimulated the development of the cluster-based nanomaterials. In this review, we will summarize some good cases of cluster structure by CALYPSO method, which have also been successfully identified by the photoelectron spectra experiments. Beginning with the alkali-metal clusters, which serve as benchmarks, a series of studies are performed on the size-dependent elemental clusters which possess relatively high stability and interesting chemical physical properties. Special attentions are paid to the boron-based clusters because of their promising applications. The NbSi12 and BeB16 clusters, for example, are two classic representatives of the silicon- and boron-based clusters, which can be viewed as building blocks of nanotubes and borophene. This review offers a detailed description of the structural evolutions and electronic properties of medium-sized pure and doped clusters, which will advance fundamental knowledge of cluster-based nanomaterials and provide valuable information for further theoretical and experimental studies. (topical review)
[en] We have investigated the effect of uniaxial and biaxial strain on the binding energy of Ge 2p, Ge 3d core level and the top of the valence band edge using x-ray photoelectron spectroscopy. The strain was measured by using a Raman spectrometer. From these results, we succeeded in the observation of the effect of uniaxial and biaxial strain on the binding energy and the top of the valence band edge. (paper)