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Analytical and Bioanalytical Chemistry (v.374, #4)

Eleventh International Conference on Solid State Analysis by Günter Marx (pp. 579-580).

Analysis of corrosion layers on protective coatings and high temperature materials in simulated service environments of modern power plants using SNMS, SIMS, SEM, TEM, RBS and X-ray diffraction studies by H. Nickel; W. Quadakkers; L. Singheiser (pp. 581-587).

In three different examples, the effects of the oxidation behaviour as well as the microstructural stability of high temperature materials and protective coatings was determined by combining the results of kinetic studies with extensive analytical investigations using, among other techniques, SNMS, SIMS, SEM, TEM, Rutherford back scattering (RBS) as well as X-ray diffraction.1) The effect of water vapour on the oxidation behaviour of 9% Cr steels in simulated combustion gases has been determined. The effects of O₂ and H₂O content on the oxidation behaviour of 9% Cr steel in the temperature range 600–800 °C showed that in dry oxygen a protective scale was formed with an oxidation rate controlled by diffusion in the protective scale. In the presence of water vapour, after an incubation period, the scales became non-protective as a result of a change in the oxidation limiting process. The destruction of the protective scale by water vapour does not only depend on H₂O content but also on the H₂O/O₂-ratio.2) The increase of component surface temperature in modern gas turbines leads to an enhanced oxidation attack of the blade coating. Improvements in corrosion resistance and longer lifetime thermal barrier coatings in gas turbines have been achieved by improvement of the high temperature properties of MCrAlY coatings by additions of minor alloying elements such as yttrium, silicon and titanium.3) The use of oxide dispersion strengthened (ODS) alloys provides excellent creep resistance up to much higher temperatures than can be achieved with conventional wrought or cast alloys in combination with suitable high temperature oxidation/corrosion resistance. Investigation of the growth mechanisms of protective chromia and alumina scales were examined by a two-stage oxidation method with ¹⁸O tracer. The distribution of the oxygen isotopes in the oxide scale was determined by SIMS and SNMS. The results show the positive influence of a Y₂O₃ dispersion on the oxidation resistance of the ODS alloys and its effect on growth mechanisms.

Keywords: Corrosion layers Coatings High temperature materials SNMS SIMS SEM TEM/RBS X-ray diffraction

Diffusion studies in non-oxide ceramics: analytical aspects of the use of ion implanted stable tracers and SIMS by H. Schmidt; P. Fielitz; G. Borchardt; S. Weber; H. Scherrer; H. Baumann (pp. 588-591).

The physical and chemical properties of complex non-oxide ceramic materials require advanced methods of diffusivity determination. In this study, we present a method based on the high-dose ion implantation of stable tracers in combination with secondary ion mass spectroscopy for depth profiling. The analytical basics, advantages and problems of the method are discussed for two examples of complex materials, the Si-B-C-N precursor ceramics and the Ti-based transition metal diborides. We demonstrate that is possible to measure the temperature dependence of diffusivities, especially for ceramic systems with low diffusivities, for systems that contain elements for which no suitable radioactive tracers exist for extended measurements.

Keywords: Diffusion Secondary ion mass spectrometry Ion implantation

SIMS investigation of CrN sputtercoatings by C. Heinisch; P. Ramminger; H. Hutter (pp. 592-596).

Chromium nitride layers produced by reactive sputtering with different process parameters were characterized with EPMA, SIMS depth profiling, and three-dimensional SIMS imaging. EPMA results are used to quantify the major components of the films while SIMS is used to gather information about the distribution of the elements chromium, silicon, nitrogen, and oxygen. For all measurements a Cs⁺ primary ion beam was applied to sputter the sample. Positive MCs⁺ (M represents the element to be analyzed) secondary ions were detected.SIMS depth profiling shows an even distribution of all major elements except oxygen, which shows significant differences in concentration and distribution depending on the process parameters. CrN layers produced at low sputter power have much higher concentration of oxygen than layers produced with high sputter power. Heating the silicon substrate during the process results in an enrichment of oxygen at the interface.

Keywords: CrN 3D-SIMS SIMS MCs+

2D- and 3D SIMS investigations on hot-pressed steel powder HS 6–5-3–8 by M. Rosner; G. Pöckl; H. Danninger; H. Hutter (pp. 597-601).

Processing of steel with powder metallurgical methods such as sintering or hot-pressing have proven to be a powerful tool for the production of industrial parts and for components in the automotive industry. Series of steel-powders (HS 6–5-3–8) produced by gas atomization has been hot-pressed in a graphite tube at temperatures from 820 °C to 1050 °C. The samples have been characterized with a Secondary Electron Microscope (SEM) due to their porosity and then investigated with 2D- and 3D- SIMS. The spatial distribution of the non-metallic impurities and the covering oxide layer of the single particles has been traced dependent to the pressing temperature.Powders pressed at temperatures higher than 880 °C exhibited different precipitation behavior of the impurities and an excessive loss of the covering oxide layer of the single powder particles.

Keywords: 3D-SIMS Powder metallurgy Hot pressing Deoxidation

Adhesion promotion of Cu on C by Cr intermediate layers investigated by the SIMS method by Karl E. Mayerhofer; Erich Neubauer; Christoph Eisenmenger-Sittner; Herbert Hutter (pp. 602-607).

Copper-carbon composites are candidate materials for heat sinks for high speed/high-performance electronic components. They combine high thermal conductivity with low density and a tailorable coefficient of thermal expansion (CTE). Because of the low wettability of carbon by copper, a thin layer of chromium can be deposited to promote both the adhesion and the thermal contact of copper with the carbon fibers. Therefore, in a first step layers of Cr and Cu were deposited by magnetron sputtering on plane vitreous carbon substrates (Sigradur G), which serve as a model for carbon fibers. From pull-off-adhesion measurements an interlayer thickness of Cr in the range of 2–10 nm was found to provide the optimal adhesion for 1 µm thick copper overlayers. To model the later serial fabrication of the composite that involves a hot pressing step following the deposition, the C/Cr/Cu samples were heat treated at 800 °C under vacuum for 1 h. Adhesion on the heat-treated samples was superior in comparison to the untreated ones. To obtain information about the adhesion mechanism secondary ion mass spectrometry (SIMS) investigations were done on the depth distribution of the main elements copper, chromium, and carbon. Two samples, one as deposited and one subjected to heat treatment after deposition, were compared in this investigation. We found that heat treatment mainly modifies the distribution of Cr in the C/Cr/Cu system.

Keywords: SIMS Deposition PVD Adhesion Diffusion

Chemical solution-deposited PbZr_0.53Ti_0.47O₃ on La_0.5Sr_0.5CoO₃. SIMS investigation of the effect of different precursor additives on the layer structure by C. Pollak; B. Malic; M. Kosec; S. Javoric; H. Hutter (pp. 608-613).

Chemical solution-deposited thin films of PbZr_0.53Ti_0.47O₃/La_0.5Sr_0.5CoO₃ on Pt/TiO₂/SiO₂/Si substrates have been investigated by dynamic SIMS. The PbZr_0.53Ti_0.47O₃ (PZT) is intended to serve as a ferroelectric layer for microelectronic or microelectromechanical applications; conducting La_0.5Sr_0.5CoO₃ (LSCO) is a buffer layer intended to eliminate fatigue effects which usually occur at the Pt/PZT interface. Depth profiles of the main components were obtained and revealed that significant diffusion occurred during the deposition and crystallisation processes. Two types of sample, with different thickness of PZT and different types of poly(vinyl alcohol) (PVA) added to the LSCO precursor, were investigated.

Keywords: SIMS Chemical solution deposition Precursor PbZrTiO LaSrCoO

TOF-SIMS and XPS-investigations of ion implanted single crystal 1b-diamonds by V. Schlett; T. Fladung; S. Dieckhoff; R. Stock (pp. 614-618).

Near surface zones of ⁴⁸Ti- and ⁵²Cr-implanted single crystal diamonds (1b-MCD) were characterized by XPS, TOF-SIMS and white light interference microscopy (WLI). By the combination of WLI and TOF-SIMS it was possible to calibrate the depth scale of TOF-SIMS and XPS depth profiles quantitatively. The adjustment of TOF-SIMS and XPS elemental depth profiles in the implantation maximum increases the quantitative detection limit of the implanted elements by more than two orders of magnitude and enables the interpretation of results from wear simulation experiments. Peak fits of XPS C_1s-photolines indicate the fraction and chemical nature of carbide-like structures in the implantation zone. Qualitative hints on carbide compounds are possibly included in the reconstructed TOF-SIMS spectra but this information can presently only be extracted with the aid of XPS analyses.

Keywords: XPS TOF-SIMS 1b-diamond Ion implantation Cutting tools

Depth profiles and resolution limits in accelerator-based solid state analysis by R. Fischer (pp. 619-625).

A ubiquitous problem in solid state analysis is the determination of the elemental composition of a sample as a function of the depth. The determination of the depth profiles from ion-beam experiments is an ill-posed inversion problem due to ion-beam and detector-induced energy spreads as well as energy-loss straggling and small-angle scattering effects. The inversion problem is solved in the framework of Bayesian probability theory, which provides a method for quantifying and combining uncertain data and uncertain additional information. By deconvolving the apparatus transfer function and modeling the scattering events in the sample we reconstructed depth profiles of ¹³C in tetrahedral amorphous carbon (ta-C) and depth profiles in ¹²C/¹³C marker probes. An enhancement of the energy resolution by a factor of 6 was obtained.

Keywords: Depth profiles reconstruction Resolution enhancement BPT

Non-destructive 3D-characterization of Zn_2–2xCu_xIn_xS₂-thin films with ion beam analysis by D. Spemann; J. Vogt; T. Butz; D. Oppermann; K. Bente (pp. 626-630).

Thin layers of ZnS-CuInS₂ mixed crystals (called ZCIS) are promising absorber materials for thin film solar cell applications. The ZCIS-films investigated in this study were grown on (001)GaP, SiO₂ and CeO₂/Al₂O₃ with different elemental compositions by Pulsed Laser Deposition (PLD). In order to optimize the sample preparation process a quantitative three-dimensional (i.e. laterally and depth resolved) determination of the compositions and thicknesses of the ZCIS-films is needed. It is demonstrated how this difficult analytical task can be addressed with ion microbeam analysis. For this purpose the films have been analysed non-destructively by means of Rutherford Backscattering Spectrometry (RBS) and Particle Induced X-ray Emission (PIXE) using a 2 MeV He⁺ ion microbeam at the high-energy ion nanoprobe LIPSION. A large variation in film thickness caused by particulates deposited on the film was observed. The elemental compositions of the film and the particulates have been determined and compared with the target composition. The deviations found varied substantially for the individual elements. It could be concluded from these measurements, that the quality of the sintered PLD-target is of crucial importance for the roughness of the films. Furthermore concentration-depth-profiles of the individual elements have been derived non-destructively by means of RBS.

Keywords: ZCIS Thin films Ion beam analysis Ion nanoprobe 3D-characterization

Electron probe microanalysis (EPMA) measurement of thin-film thickness in the nanometre range by M. Procop; M. Radtke; M. Krumrey; K. Hasche; S. Schädlich; W. Frank (pp. 631-634).

The thickness of thin films of platinum and nickel on fused silica and silicon substrates has been determined by EPMA using the commercial software STRATAGEM for calculation of film thickness. Film thickness ranged in the order 10 nm. An attempt was made to estimate the confidence range of the method by comparison with results from other methods of analysis. The data show that in addition to the uncertainty of the spectral intensity measurement and the complicated fitting routine, systematic deviation caused by the underlying model should be added. The scattering in the results from other methods does not enable specification of a range of uncertainty, but deviations from the real thickness are estimated to be less than 20%.

Keywords: Electron probe microanalysis, EPMA Thin films Thickness measurement X-rays

Investigation of interfacial interaction between uncoated and coated carbon fibres and the magnesium alloy AZ91 by A. Dorner-Reisel; Y. Nishida; V. Klemm; K. Nestler; G. Marx; E. Müller (pp. 635-638).

Unidirectionally reinforced metal–matrix composites with a fibre volume content between 63 and 68% were processed by squeeze casting using T800 H carbon fibres and the magnesium alloy AZ91. The surface of the fibres was prepared by thermal desizing of the fibres or by deposition of a pyrolytic carbon (pyC) coating. Different interfacial conditions could be identified by transmission electron microscopy (TEM) and the single-fibre push-in test. TEM confirmed the formation of needle-like phases at the fibre surface or, for coated fibres, within the pyrolytic carbon coating. During loading by the Vickers type indenter an intense response was observed for composites of coated fibres and the magnesium alloy. This could by caused by stick–slip effects within the pyrolytic carbon coating.

Keywords: Metal–matrix composites Transmission electron microscopy Interface

High-resolution analytical TEM of nanostructured materials by R. Schneider (pp. 639-645).

This paper briefly reviews the potential applicability of analytical transmission electron microscopy (TEM) to elucidate both structural and chemical peculiarities of materials at high lateral resolution. Examples of analytical TEM investigations performed by energy-dispersive X-ray spectroscopy (EDXS), electron energy loss spectroscopy (EELS), and energy-filtered TEM (EFTEM) are presented for different materials systems including metals, ceramics, and compound semiconductors. In particular, results are given of imaging the element distribution in the interface region between γ matrix and γ' precipitate in the nickel-based superalloy SC16 by energy-filtered TEM. For core-shell structured BaTiO₃ particles the chemical composition and even the chemical bonding were revealed by EELS at a resolution of about 1 nm. A sub-nanometer resolution is demonstrated by energy-selective images of the Ga distribution in the surrounding of (In,Ga)As quantum dots. Moreover, the element distribution in (Al,Ga)As/AlAs multilayers with linear concentration gradients in a range of about 10 nm was investigated by EDXS line-profile analyses and EFTEM.

Keywords: Nanostructured materials Analytical electron microscopy Energy-dispersive X-ray spectroscopy Electron energy loss spectroscopy Energy-filtered TEM

Calibration of XPS – energy scale for determination of the oxidation states of doping elements in SnO₂ powders by D. Dobler; S. Oswald; K. Wetzig (pp. 646-649).

X-ray photoelectron spectroscopy (XPS) has been used to investigate the oxidation states of doping elements in doped SnO₂ powders. Because of low conductivity, however, charging and resulting peak shift is observed. To obtain the real peak position a suitable reference peak must be found in the XPS spectrum. In this study both internal (Sn3d_5/2 peak) and external references (Au4f_7/2 and C1 s) were examined. When external references were used a shift of all the peaks studied was observed; the extent of this depended on the doping element and the doping concentration. By doping with an element of valence >4 (Nb and Sb) we obtained peaks at binding energy (BE); doping with a trivalent element (In) led to peaks at values of the BE. This peak shift is connected with changes of Fermi level. In contrast, by using Sn3d_5/2 as reference we obtained results which enabled, for example, observation of the dependence of changes of the oxidation state of Sb on doping concentration.

Keywords: XPS Tin oxide Charging effects

Synchrotron-induced photoemission of GaAs electrodes after electrochemical treatment in aqueous electrolytes by M. Beerbom; Th. Mayer; W. Jaegermann; D. Batchelor; D. Schmeißer (pp. 650-653).

Electrochemically-induced oxidation and reduction reactions of UHV-cleaved GaAs(110) surfaces have been studied after emersion under potential control using high resolution synchrotron-induced photoelectron spectroscopy. High quality spectra of the As and Ga core 3d lines and the valence band region have been obtained. The spectra of the anodic oxide show strong emission of bulk-like Ga₂O₃ and some As₂O₃ with the admixture of suboxides and hydroxides. Ga₂O₃ and As₂O₃ are cathodically reduced leaving the GaAs surface covered mostly with elemental As, some As-H and remnants of Ga-suboxides and -hydroxides.

Keywords: GaAs Electrochemistry Aqueous electrolytes Surface engineering Semiconductor preparation Synchrotron

Ellipsometric study of the change in the porosity of silica xerogels after chemical modification of the surface with hexamethyldisilazane by C. Himcinschi; M. Friedrich; S. Frühauf; I. Streiter; S. Schulz; T. Gessner; M. Baklanov; K. Mogilnikov; D. Zahn (pp. 654-657).

Variable angle spectroscopic ellipsometry (VASE) and ellipsometric porosimetry (EP) have been used to study the effect of treatment with hexamethyldisilazane (HMDS) on the porosity of silica xerogel films. Chemical modification of the surface with HMDS was found to reduce the porosity by ~15%. This reduction was connected with changes which occur in the silica network, with further condensation or the reaction between neighbouring trimethylsilyl (TMS) surface groups being possible causes.

Keywords: Ellipsometry Low-k dielectric Xerogel

Characterization of thin polymer and biopolymer layers by ellipsometry and evanescent field technology by T. Mutschler; B. Kieser; R. Frank; G. Gauglitz (pp. 658-664).

The characterization of sensitive layers is the prerequisite for the optimization of chemical and biochemical sensors. The application of SE (Spectral Ellipsometry) and SPR (Surface Plasmon Resonance) as methods of characterization of such sensitive layers is discussed. In combination with infrared spectroscopy, the properties of polymer networks, micro-porous polymers, liquid crystals, and biomimetic polymers can be examined regarding their applicability for optical sensing. Apart from the basic principles regarding the characterization approaches, applications in the area of environmental sensing, optimization of hydrogel layers for antigen/antibody interaction, and discrimination of analytes in homologous series of alcohols are discussed. The effects of analytes on the phase transition in combination with disordering of liquid crystals are given.

Keywords: Ellipsometry Surface plasmon resonance Microporous polymers Biopolymers Liquid crystals

Infrared ellipsometric view on monolayers: towards resolving structural details by E. Korte; U. Schade; W. Peatman; A. Röseler; D. Tsankov; K. Hinrichs (pp. 665-671).

The optical constants in the infrared spectral range and the thickness of a surface layer are simultaneously determined by reflection based spectroscopic infrared ellipsometry. In the past experimental progress has been used to increase sensitivity with the aim to detect ever thinner layers. Reaching the monolayer limit by now, methodic efforts focus on revealing structural details such as anisotropy and lateral heterogeneity caused primarily by molecular orientational order. The basis of the method and present methodical approaches are outlined. Aspects of using synchrotron radiation for infrared ellipsometry and of setting up an infrared beamline are discussed.

Keywords: Infrared ellipsometry Monolayer Surface analysis Anisotropy Synchrotron radiation Molecular orientation

Infrared-optical properties of vapour-deposited metal films by Martin Buskühl; Ernst-Heiner Korte (pp. 672-675).

Spectroscopic infrared ellipsometry was applied to determine the optical constants of thin metal layers deposited on dielectric substrates such as glass or CaF₂. The layers were produced by evaporating gold or silver in a vacuum, and the coverage, that is the deposited mass per area, was chosen in the range 80–1200 mg m^–2 for gold, which refers to thicknesses in the lower nanometer range; in the case of the specifically lighter silver, about half the coverage was applied. At low coverage a metal island structure is obtained, which gives rise to surface-enhanced infrared absorption (SEIRA). Depending on the coverage, the deposited films exhibit either dielectric or metallic optical properties. Atomic force microscopy and conductivity measurements complement the spectroscopic observation.

Keywords: Infrared ellipsometry Optical constants Thin films Metal island films SEIRA

Characterization of wet-chemically treated silicon interfaces by surface photovoltage measurements by H. Angermann (pp. 676-680).

A non-destructive and surface-sensitive surface photovoltage (SPV) technique was employed to investigate the influence of important wet-chemical treatments on the electronic surface properties. The preparation-induced surface roughness as well as the hydrogen and oxide coverage were additionally determined by spectroscopic ellipsometry (SE).High values of interface charge and a high density of rechargeable interface states were observed on atomically rough surfaces and interfaces after HF-treatment and conventional wet-chemical oxidation. Both interface charge and density of rechargeable interface states could be reduced significantly by preparing an atomically flat Si surface and a well-ordered silicon/silicon oxide interface by applying special H-termination and hot-water oxidation procedures.

Keywords: SPV Wet-chemical treatments Surface properties Spectroscopic ellipsometry

Characterization of laser-irradiated YNi₂B₂C surfaces by Auger electron spectroscopy by S. Baunack; A. Plotnikov; R. Wrobel; C. Vogt; K. Wetzig (pp. 681-684).

The suitability of laser ablation inductively coupled plasma mass spectrometry (LA–ICP–MS) for precise analysis of YNi₂B₂C has been investigated. The intensity ratios B/Y and Ni/Y were found to vary during ablation as a function of the ablation conditions. This could be because of fractionation, owing to incongruent ablation or transport and plasma effects. The bottoms and surroundings of the craters were investigated by scanning Auger electron spectrometry. The bottoms of the craters produced by ablation are covered with a thin oxide comparable with that on the polished crystal surface.The craters are surrounded by an oxide layer the dimensions and thickness of which depend on the laser conditions. The formation of this oxide can be assumed to be a result of partial oxidation of sample material during the ablation process; the oxide is then redeposited around the laser crater.

Keywords: Laser ablation Auger electron spectroscopy ICP–MS Borocarbides

STM and STS of coronene on HOPG(0001) in UHV – adsorption of the smallest possible graphite flakes on graphite by Markus Lackinger; Stefan Griessl; Wolfgang M. Heckl; Michael Hietschold (pp. 685-687).

The adsorption of the aromatic molecule hexabenzobenzene (coronene) on an HOPG(0001) surface was investigated under UHV conditions by means of variable temperature scanning tunneling microscopy (STM) and spectroscopy (STS). Imaging on a mesoscopic scale showed a distribution of coronene islands. These islands are mobile on the surface and can be pinned at step-edges. Zooming in on areas apart from the islands reveals an hexagonal arrangement of coronene molecules in a closed layer. Submolecular resolved molecules consist of bright spots with varying intensity. This variation in intensity is explained with the commensurability of the adlayer. STS investigations were performed for various tip-sample distances, adjusted by the tunneling current setpoint. A gap can be seen for every setpoint, but its width is dependent on the setpoint. The gap for the largest tip-sample distance and therefore the smallest tip-sample interaction is compared with the theoretical value.

Keywords: STM STS Coronene Adsorbate HOPG

Study by scanning tunneling microscopy of hydrogen adsorption and desorption on Si(111)7×7 at room temperature and at high temperature by A. Kraus; M. Hanbücken; T. Koshikawa; H. Neddermeyer (pp. 688-694).

An overview is given on the use of scanning tunneling microscopy (STM) for investigation of the adsorption of hydrogen on Si(111)7×7 both at room temperature and at elevated temperature to finally obtain a hydrogen-saturated surface of Si(111). The initial stages are characterized by high reactivity of Si adatoms of the 7×7 structure. After adsorption of hydrogen on the more reactive sites in the beginning of the adsorption experiments a regular pattern, which is different for room and elevated temperature, is observed for the less reactive sites. In agreement with previous work, local 1×1 periodicity of the rest atom layer and the presence of di- and trihydride clusters is observed for hydrogen-saturated surface. STM has also been used to characterize surfaces from which the hydrogen atoms have been removed by thermal desorption. Finally, tip-induced desorption by large positive sample-bias voltages and by increasing the tunneling current will be described.

Keywords: Scanning tunneling microscopy Hydrogen Si(111)7×7 Adsorption Desorption

Nanostructure and thermoelectric properties of ReSi_2±x thin films by J. Thomas; D. Hofman; C. Kleint; J. Schumann; K. Wetzig (pp. 695-698).

Anomalies in the nanostructure evolution of ReSi_2±x thin films have proved to be of large interest in connection with their thermoelectric properties. By means of electron microscopic methods the correlation between structural properties and transport behaviour has been studied. The short-range order of the amorphous state was characterised by reduced density functions calculated from diffuse electron diffraction diagram and is found to correlate with the temperature dependence of the electrical resistance. The crystallisation process observed in situ in the transmission electron microscope starts with the formation of relatively large ReSi_1.75 grains (up to 100 nm). In later stages, only smaller grains are growing. This leads to a decrease in the mean grain size and to the increase of the nanocrystalline volume fraction during the heat treatment. This behaviour allows the investigation of the thermopower as function of the nanocrystalline volume fraction. Thus, at a nanocrystalline content of about 35% the thermopower exhibits a maximum in accordance with calculations.

Keywords: Rhenium silicide Thermoelectricity Nanocrystallites TEM Electron diffraction

Phase discrimination by automated BKD by Robert Schwarzer (pp. 699-702).

Automated backscatter Kikuchi diffraction in the SEM enables rapid discrimination of phases and the automated acquisition of phase-distribution maps at sub-micron resolution, if the phases belong to different Laue groups and/or if their lattice constants are significantly different. The acquired database can be further used for quantitative determination of phase contents, for construction of crystal orientation maps, for characterization of grain and phase boundaries, for crystal texture analysis on a grain-specific level by calculating pole figures and orientation density functions separately for each phase, and for orientation stereology in general. Pattern-quality maps provide a clear reproduction of the microstructure on a meso-scale level.

Keywords: Phase discrimination Ferritic–austenitic steel BKD EBSD ACOM Crystal texture

Potential of cathodoluminescence (CL) microscopy and spectroscopy for the analysis of minerals and materials by Jens Götze (pp. 703-708).

The present study summarizes results of cathodoluminescence (CL) microscopy and spectroscopy applied to minerals and materials. CL can be used both in a purely descriptive way to detect and distinguish different minerals or mineral generations by their variable CL colours or as an effective method for spatially resolved analysis of point defects in solids by spectral CL measurements. The cathodoluminescence emission is in all cases either related to lattice defects (e.g. electron defects on broken bonds, vacancies or radiation induced defects) and/or to trace activator ions such as REE^2+/3+, Fe³⁺, Cr³⁺, Al³⁺, Mn²⁺, Pb²⁺, Cu²⁺, Sn²⁺ or uranyl groups. CL spectroscopy is an outstanding method to characterize the degree of purity of materials or to detect trace elements in natural and synthetic minerals. In this way, alterations, diffusion of trace elements or formation of new phases are successfully detectable even in the case of materials with heterogeneous texture and high contents of non-crystalline phases.

Keywords: Cathodoluminescence Microscopy Spectroscopy Minerals Materials

Influence of the composition of BCN films deposited by reactive magnetron sputtering on their properties by C. Martínez; S. Kyrsta; R. Cremer; D. Neuschütz (pp. 709-711).

Compounds of the B–-C–-N system are very promising to produce superhard coatings with good tribological, chemical, and thermal properties. To investigate the influence of the composition of BCN films on their properties, films with five different compositions at nearly constant nitrogen content were deposited on silicon wafers by magnetron sputtering from hexagonal boron nitride and graphite targets operated in RF and DC mode, respectively. The compositions and binding states of the films were determined by XPS. The nitrogen content was found to be almost constant for all films at about a 40 at-%, whereas boron and carbon compositions ranged between 15–35 and 25–50 at-%, respectively. The electronic and bonding structure of the coatings were analyzed by REELS using three different electron beam energies to obtain information at different depths. An increase of the carbon content of the films resulted in a significant shift of the π–π* interband transition with respect to the energy loss corresponding to h-BN. The absence of the π–π* transition in the energy loss spectra acquired at a beam energy of 1900 eV indicates the existence of a very thin overlayer mostly sp ² bonded and probably with a distorted hexagonal structure. The position of the bulk plasmon losses corresponded to the hexagonal phase for the overlayer and presented a shift of more than 1.5 eV to the higher energy loss direction for the spectra obtained at 1900 eV beam energy. This shift and the absence of the sp ²-bond fingerprint induced the possibility of an underlying disordered structure with a majority of sp ³ bonds.

Keywords: Boron carbonitride XPS REELS

Structure and composition studies of chemical vapour-deposited BCN fibre coatings by Dagmar Dietrich; Ulrich Roll; Sabine Stöckel; Kathrin Weise; Günter Marx (pp. 712-714).

The composition and structure of boron carbonitride (BCN) films were studied. The films were continuously deposited on fibres by atmospheric pressure CVD. The precursors were ammonia, trimethyl borate and toluene. The composition was determined by photoelectron spectra of boron 1s, nitrogen 1s, carbon 1s and oxygen 1s. By fixing the C 1s peak at 285 eV, the position of the B 1s peak and the N 1s peak in the BCN films was equal to BN films. The C content of the films increases from about 6 at% to 60 at%, leaving the stoichiometric boron/nitrogen ratio as well as the oxygen content below 10 at% unchanged. Generally, the carbon content in the films is lower than predicted by the precursor ratios. Obviously, the insertion of carbon into the film is decreased in the presence of ammonia, which is known to etch carbon. With a decreasing ammonia/toluene ratio, the undesired effect in the reaction is suppressed and the carbon deposition becomes considerable. Transmission electron microscopic studies were performed on cross-sections of the coated fibres. High-resolution images generally show a hexagonal turbostratic structure with different orientation preferences of the atomic lamellae similar to hexagonal turbostratic boron nitride and pyrolytic carbon. When a noticeable carbon concentration (20 at%) is reached, the atomic sheets become uniformly distributed in all directions in space.

Keywords: XPS TEM CVD fibre coatings BCN films

Study of the structure of passivated vanadium–titanium alloys and their semiconductor properties by T. Bachmann; W. Vonau; P. John (pp. 715-719).

The possibility of investigating the photocurrent behavior and structure of electrochemically prepared passive films on metallic titanium and on binary vanadium–titanium alloys has been demonstrated. The semiconductor properties were characterized by measuring the dependence of the photocurrent on the wavelength of the incident light and on the electrode potential. The results showed the oxide layers to be n-type semiconductors with a bandgap between 2.6 and 3.3 eV and a flatband potential of approximately –300 to +400 mV (relative to the SCE). The results were interpreted in terms of the corrosion characteristics of the materials. XPS measurements on pure vanadium and some alloys are presented. Several properties were used to characterize the passive surface of these materials. The V₂O₅ and TiO₂ content decreases with increasing depth.

Keywords: Hydrogen peroxide sensor Passivity Photocurrent behavior Semiconductor properties Vanadium–titanium alloy

Kinetic aspects of the formation of aluminium oxide by use of a microwave-induced plasma by A. Quade; H. Steffen; R. Hippler; H. Wulff (pp. 720-723).

The oxidation of thin aluminium layers in a microwave plasma has been investigated to determine the kinetics of oxide growth.Thin Al-coatings were oxidized by means of a variety of gas mixtures, characterized by different partial pressures of oxygen, in microwave-induced plasmas of different power. To study the whole kinetic process the Al-metal and the oxide formed were investigated by means of a combination of grazing incidence X-ray reflectometry (GIXR) and grazing incidence X-ray diffractometry (GIXRD). XPS and FTIR spectroscopy confirmed the formation of stoichiometric Al₂O₃ . The alumina formed is X-ray amorphous. Quantitative description of oxide formation was achieved indirectly by determination of the decrease in the integrated intensity of the Al(111)-peak and the total thickness of the whole coating. These values enabled calculation of kinetic data.It was found that oxide growth was a combination of two simultaneous processes – diffusion and sputter processes. The diffusion coefficient D (cm² s^–1) and the sputter rate S (nm s^–1) were determined. The effect of the composition of the gas mixture, microwave power, and concentration of activated oxygen species on the oxidation process will be discussed. For calculation of the activation energy, E_A, of this plasma-enhanced diffusion process the temperature-dependence of D was investigated.

Keywords: Aluminium Plasma oxidation Diffusion Grazing incidence X-ray reflectometry (GIXR) Grazing incidence X-ray diffractometry (GIXRD)

Formation and nitridation of vanadium–aluminum intermetallic compounds by H. Lewalter; W. Bock; B. Kolbesen (pp. 724-731).

V₅Al₈ and V₃Al intermetallics have been formed by interdiffusion, by annealing of sputtered V/Al-multilayers at 700 °C in vacuo; sapphire (102) was used as substrate. The V/Al intermetallics were nitridated in NH₃ at 900 °C for 1 min by RTP (rapid thermal processing). The samples were investigated with XRD (X-ray diffraction), SNMS (secondary neutral mass spectrometry), and AFM (atomic force microscopy). A 5–10 nm thick AlN film (001 textured) was formed by nitridation of V₅Al₈ (110 textured) and 2–3% nitrogen was incorporated in the V₅Al₈ bulk . Nitridation of V₃Al resulted in the formation of VN and AlN. Direct nitridation of V/Al-multilayers showed that near the surface nitridation is faster than intermixing of the V and Al layers. The capability of VN as diffusion barrier for Al could also be shown.

Keywords: Vanadium Aluminum Intermetallics Ammonia Nitride Nitridation Nitrogen Sapphire Rapid thermal processing (RTP)

Electron beam induced changes in transition metal oxides by D. Su (pp. 732-735).

Electron beam induced changes in maximal valence transition metal oxides V₂O₅, M_oO₃ and TiO₂ (anatase) were studied by means of electron energy-loss spectroscopy and electron diffraction in transmission electron microscopy. For V₂O₅, the observed chemical shifts of the L-edge reveal the reduction of V⁵⁺ to V²⁺. The structure changes from orthorhombic V₂O₅ to cubic VO. MoO₃ can be reduced to a phase with an oxidation state less than that in MoO₂. No notable structural or electronic change in TiO₂ (anatase) is observed. The different behaviours of the studied oxides under an electron beam are discussed with respect to bonding energy and lattice structure.

Keywords: Transition metal oxides Reduction Oxidation state Electron beam Transmission electron microscopy

Model investigations on the effect of Si transport on the nanocrystallization of amorphous FeSiB-(Cu,Nb) by S. Oswald; S. Baunack; G. Henninger; D. Hofman (pp. 736-741).

Amorphous material of the class FeSiB-(Cu,Nb) has been investigated with a background of soft-magnetic application of the corresponding nanocrystalline material. Thin-film analytical methods (SIMS, AES, TEM) have been used to study the diffusion of Si in such materials prepared as layer systems by magnetron sputter deposition. Significant interdiffusion occurs even at low temperatures – approximately 400 °C. Quantitative description failed, however, because formation of new iron monosilicide phases begins above this temperature. It is concluded that only high-mass-resolution SIMS or radioactive tracer analysis can be used for successful acquisition of information at this material system.

Keywords: Diffusion Nanocrystals Phase formation Magnetic material Depth profiling

In situ surface analysis of annealed Fe-1.5%Mn and Fe-0.6%Mn low alloy steels by C. Martínez; R. Cremer; D. Neuschütz; A. von Richthofen (pp. 742-745).

The oxidation of two binary alloys, Fe-1.5%Mn and Fe-0.6%Mn, was studied in terms of the annealing conditions and paying special attention to the selective oxidation of manganese. The crystallographic structure of the surfaces and their compositions were determined by RHEED and XPS by using in situ analytical devices attached to the annealing reactor to avoid surface contamination after the treatments. Additionally, ex situ investigations on the morphology and composition of the surfaces were performed by FEG-SEM, WDX, and GIXRD. The annealing processes were performed at 800 °C under N₂-5%H₂ protective atmospheres at water vapor dew points between –10 and –30 °C. The oxides formed were identified and the resulting surface structures resolved.

Keywords: Selective oxidation Fe-Mn XPS RHEED

The supramolecular structure of ultrafiltration membranes synthesized by electropolymerization by L. Kolzunova; N. Barinov (pp. 746-748).

The structure and morphology of polyacrylamide–formaldehyde ultrafiltration membranes synthesized by electropolymerization of monomers have been investigated by scanning electron microscopy and scanning tunneling microscopy. The conclusion is that the polymeric film consists of crystalline and amorphous phases. Spherulites occur throughout the entire thickness of the membrane matrix and make the whole structure rigid. The amorphous phase is penetrated by pores directed perpendicularly to the membrane surface. The membranes have an anisotropic sandwich structure with the selective layer formed on the side of the polymer film facing the electrode.

Keywords: Electropolymerization Ultrafiltration membrane Supramolecular structure

A new attempt to study biomineralised silica bodies in Dactylis glomerata L. by Dagmar Dietrich; Steffen Hemeltjen; Norbert Meyer; Ernst Bäucker; Gebhardt Rühle; Otto Wienhaus; Günter Marx (pp. 749-752).

The accumulation process of inorganic compounds in animals and plants by biomineralisation is not well understood nowadays, though it may be the key to an environmental-compatible production of modern materials in future. In this paper a new attempt will be made on the investigation of silica accumulation in grasses (especially Dactylis glomerata L.). The silicic acid agglomerates in Dactylis glomerata L. were studied by means of scanning electron microscopy in combination with energy dispersive X-ray spectrometry as well as infrared and micro-RAMAN spectrometry.In particular blades were prepared by critical point drying or shock-freezing for anatomical studies of silica cells and bristles in the plant tissue. SEM imaging and EDX microanalysis for elemental composition were done in the cryostage as well as under variable pressure . The localized silica bodies were examined for their structural properties by means of IR and micro RAMAN spectroscopy. The results are comparable to SiO₂ polytypes such as high disperse silica and opal.

Keywords: Scanning electron microscopy EDX microanalysis IR spectroscopy RAMAN spectroscopy Silica bodies

Diamond-like carbon coatings with Ca-O-incorporation for improved biological acceptance by A. Dorner-Reisel; C. Schürer; G. Irmer; F. Simon; C. Nischan; E. Müller (pp. 753-755).

Diamond-like carbon (DLC) coatings were modified by doping the thin films with Ca-O compounds. Raman spectroscopy indicates growth of sp²-hybridised, ordered regions in size and/or number within the amorphous carbon–hydrogen network as a result of the Ca-O-incorporation. CaCO₃ was identified by X-ray induced photoelectron spectroscopy. Proliferation and morphology of L929 mouse fibroblasts reveal improved biocompatibility of Ca-O-modified DLC.

Keywords: Diamond-like carbon Biocompatibility Hardness Microstructure

Sliding-spark spectrometry of sediment samples by H. Angeyo; K. Flórían; A. Golloch; V. Vojtekovà (pp. 756-763).

Direct analysis of non-conducting solids and dielectric surface layers for elements at trace levels has been shown to be feasible by the new so-called sliding-spark spectroscopy, in which a discharge plasma is bound by, and propagates on, the surface of a dielectric sample matrix. By using a river sediment as a model matrix, bound in PVC to improve elemental atomization and excitation efficiency, as a result of the formation of volatile chlorides, the potential of the technique for environmental applications has been investigated by studying the characteristic UV–visible radiation emitted in the wavelength range 210–510 nm for the elements Fe, Cr, Ni, Cu, Pb, Cd, Zn, Co, V, Ti, and Mn. The radiation was detected by means of a CCD spectrometer and analysed for spectral line identification, selection, and the linearity of the spectral response, to determine whether this was suitable for establishing a calibration strategy for quantitative analysis using the sliding-spark source.

Keywords: Sliding-spark spectroscopy Trace element analysis Calibration strategy Non-conducting solids Sediment

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Analytical and Bioanalytical Chemistry (v.374, #4)