FeMn-based alloys are promising materials for vascular implant applications, especially due to their superior mechanical properties and excellent processability. However, a further increase of the biodegradation rate of these metallic materials is desired. The addition of silver was reported to be a promising approach for accelerating the corrosion rate of those FeMn-based alloys by promoting local corrosion due to galvanic coupling, besides improving their antibacterial properties. On the other hand, the corrosion mechanisms occurring due to silver addition in various FeMn-based systems have not been understood completely. In this study, the effect of different silver contents (0.6 wt% and 1.2 wt%) on the microstructure, mechanical and corrosion properties of a cast biodegradable Fe-30Mn-6Si (wt%) is presented. By silver addition, finely distributed Ag-rich precipitates are formed in the matrix composed of austenite and epsilon-martensite, which could be detected by investigations with scanning electron and transmission electron microscopy as well as X-ray diffraction. Furthermore, an enhanced epsilon-martensite fraction was observed with rising Ag content. These changes in the microstructure significantly influence the corrosion properties. By means of potentiodynamic polarization measurements in a simulated body fluid (SBF) at 37 degrees C, it was revealed that the Ag additions reduce the corrosion current density, which indicates a decreased corrosion rate in comparison to Fe-30Mn-6Si. However, the alloy modifications still show higher corrosion current densities than a cast Fe-30Mn reference system. In addition, higher yield strengths for Agadded alloys were detected by quasi-static tensile and compression tests. Data availability: The processed data required to reproduce these findings cannot be shared at this time as the data also forms part of an ongoing study.

Microsecond Pulsed Glow Discharge (μs-PGD) was applied to commercially available spectrometers specified for OES elemental analysis with Grimm type sources, in order to have a look at the benefits which PGD can bring for practical bulk analysis.

Computational study of ICP in a low-argon-flow and standard Fassel-type torches and comparison with experimental results.

This article describes the compositional depth profiling (CDP) of diamond-like carbon (DLC) layers by Glow Discharge-Optical Emission Spectrometry (GD-OES).

Beta-type Ti-40Nb with very low Young's modulus is a promising alloy for long-term bone implant applications but surface states must be tailored for optimum osseointegration. Different anodization methods for surface oxidation were evaluated and oxide layers with characteristic morphologies were obtained. Anodization in fluoride-containing solutions generates oxide nanotubes with higher aspect ratio than those grown on CP2-Ti. The electrolyte composition has some influence on the oxide morphology. Plasma electrolytic oxidation in strongly alkaline solution yields a two-layer oxide structure with a thin compact inner layer and a much thicker outer layer with micropores and microchannels. Inductively coupled RF oxygen plasma anodization causes the formation of microstructured oxides on the Ti-40Nb surface. With increasing processing temperature a transition from random structured to patterned oxides was observed which is opposite to the trend for CP2-Ti. For all three techniques the oxide layer growth on the Ti-40Nb alloy follows the principal mechanisms that are established for Ti. Nb species are involved in the oxidation processes which causes significantly enhanced layer thickness growth, morphological changes and mixed oxides (TixNb1 − x)O2, more specific (Ti0.75Nb0.25)O2. All obtained oxide types appear to be promising as coatings of beta-type implants with appropriate bioactivity to stimulate bone growth.

Two commonly used discharge cells (Grimm type and hollow cathode) were studied and compared in respect of their analytical capabilities. Semiconductive (silicon, silicon carbide, gallium nitride) and nonconductive (quartz and alumina) samples were considered. In this connection a combined hollow cathode was used, which consists of a cylindrical cathode and a flat sample in the bottom of the cylinder. Aluminum, copper, and tantalum cylindrical cathodes were applied. The comparison of the discharge cells was made by the OES signal intensities of sample components at equal power and similar pressure conditions, either at continuous RF or pulsed DC power supply modes. Operating in continuous RF mode, the combined hollow cathode source was shown to give almost the same or higher intensities compared with the Grimm cell. The application of the hollow cathode with continuous RF mode has an appreciable advantage only for thick dielectric samples, because in contrast to the Grimm cell, for the hollow cathode the analytical signal was found to be independent on sample thickness. Operating in pulsed DC mode, the combined hollow cathode system produces up to several orders of magnitude higher intensities than the Grimm cell, especially for dielectric samples. The pulsed mode has also shown good ratios of sample to cathode intensities compared with the continuous one. The sputtering mechanism in the combined hollow cathode cell was investigated and found to be connected with the formation of a thin conductive layer on the sample surface. The composition and thickness of the latter, depending on operating parameters and sputtering time were studied. It was shown that the surface layer is generated as a result of hollow cathode disc material deposition, sample material redeposition and enrichment of the less sputtered sample component.

The excitation of Cu+ ions in a Ne glow discharge with small additions of H2, O2 and N2 was studied. Ratios of radiative transition rates between different Cu II levels in a discharge in neon, with and without the molecular gas added, were calculated, and the formalism of transition rate ratio (TRR) diagrams was developed and used to study the changing excitation conditions. Virtually no changes in the excitation of Cu+ ions occur in a neon discharge if nitrogen is added. Additions of hydrogen and oxygen to neon as the discharge gas affect excitation of the 4d, 5s and some other Cu II levels in the vicinity of the ionization energy of neon (21.56eV). Also some lower Cu II levels, excited by radiative decay of those higher energy levels, are affected. The 4p 3P2 level at 15.96eV is enhanced by additions of hydrogen. It was suggested that this enhancement is caused by the asymmetric charge transfer reaction between neutral copper atoms and the H2+ molecular ions.

We report results of comprehensive studies using the Nu Instruments Astrum high-resolution glow discharge mass spectrometer (GD-MS) and optical emission spectrometry (OES) to investigate the relative importance of discharge mechanisms, such as Penning ionization (PI) and asymmetric charge transfer (ACT), at low-power/low-pressure discharge conditions. Comparison of the ratios of the ion signals of each constituent element to that of the plasma gas shows that for oxygen, the ratio in krypton is more than ten times higher than in argon (oxygen ground state ions are produced by Kr–ACT). For many elements, the ratios are very similar but that for tungsten is higher with krypton, while for iron, the reverse holds. These effects are linked to the arrangement of ionic energy levels of the elements concerned and the resulting relative importance of ACT and PI. The GD-MS and GD-OES results have shown that the ACT process can play an important role as the ionization mode in low-power/low-pressure discharges. However, OES results have shown that the magnitude of change in spectral intensities of elements studied are dependent on the discharge conditions.

To investigate the process temperature on the growth of ultra-thin (≤500nm) Cu(In,Ga)Se2 (CIGSe) absorbers and the corresponding performance of solar cells, the process temperature was set to 610°C and 440°C, respectively. It was found that the low process temperature (440°C) could reduce the inter-diffusion of Ga–In and thus result in a higher back [Ga]/([Ga]+[In]) ([Ga]/[III]) grading than at the temperature of 610°C. The higher back [Ga]/[III] grading at 440°C was evidenced to both electrically and optically contribute to the efficiency enhancement of the solar cells in contrast to the lower back [Ga]/[III] grading at 610°C. It was also implied that the high back [Ga]/[III] grading was beneficial to the collection of carriers generated from the back-reflected light.

For the first time RF voltage and current were measured directly at the ICP load coil.

The plasma emission pre-peaks of many atomic and ionic spectral lines of Cu and Ar were systematically investigated in a Grimm-type pulsed glow discharge (PGD). To register the pre-peaks with sufficient time resolution, a monochromator with photomultiplier detection was used. When the applied power exceeded a specific threshold, pre-peaks were found in all spectral lines investigated, and it was revealed that the electrical pre-peak was the cause of the atomic emission pre-peak. The form and intensity of the pre-peak radiation were, however, found to be different for different atomic emission lines. The excitation energy of the upper energy level of the atomic line transition, and factors related to recombination and self-absorption, were found to affect the emission pre-peak. Pre-peaks observed when using pulsed DC and pulsed radio-frequency power were compared. This investigation provides insight into best practice when selecting spectral lines most suitable for analytical spectrometry using PGD.

When producing slices from Cu(In,Ga)(S,Se)(2) thin films for solar cells by use of a focused ion beam (FIB), agglomerates form on the Cu(In,Ga)(S,Se)(2) surfaces, which deteriorate substantially the imaging and analysis in scanning electron microscopy. Similar problems are also experienced when depth-profiling Cu(In,Ga)(S,Se)(2) thin films by means of glow-discharge or secondary ion mass spectrometry. The present work shows that the agglomerates are composed of (mainly) Cu, and that their formation may be impeded considerably by either cooling of the sample or by use of reactive gases during the ion-beam sputtering. The introduction of XeF(2) during FIB slicing resulted in excellent images, in which the microstructures of most layers in the Cu(In,Ga)(S,Se)(2) thin film stack are visible, including the microstructure of the 20 nm thin MoSe(2) layer. Acquisition of high-quality two-dimensional and also three-dimensional electron backscatter diffraction data was possible. The present work gives a basis for enhanced SEM imaging and analysis not only in the case of Cu(In,Ga)(S,Se)(2) thin films but also when dealing with further material systems exhibiting similar formations of agglomerates.

A Monte-Carlo based model is developed for simulating the evolution of Ar concentration, temperature and flow in time and space. Potentially, the model could be used for gas simulations in a wide range of different applications. Here, the model is incorporated into an existing but modified model of a microsecond pulsed glow discharge (mu s PGD) in a Grimm-type plasma excitation source. Results of the simulations reveal that a thermal mechanism is responsible for the formation of the electrical prepeak and pressure waves, two phenomena that take place at the leading edge of the ms pulse in this source.

A novel Acousto-Optical imaging Spectrometer (AOS) was developed with unique features that make it attractive for different applications and fundamental investigations in atomic spectroscopy. Spatial resolution of the AOS is approximately 125 μm. Spectral resolution varies from 0.05 nm to 0.3 nm (full width at half maximum, FWHM) between 250 nm and 800 nm, respectively. Time resolution is 5 ns. Thus, the constructed AOS provides enough spatial, spectral and time resolution for applications in glow discharge imaging spectroscopy. Fast switching between different spectral lines within 200 μs can be used e.g. to investigate the evolution of different spectral lines quasi-simultaneously.

The present work shows results on elemental distribution analyses in Cu(In,Ga)Se2 thin films for solar cells performed by use of wavelength-dispersive and energy-dispersive X-ray spectrometry (EDX) in a scanning electron microscope, EDX in a transmission electron microscope, X-ray photoelectron, angle-dependent soft X-ray emission, secondary ion-mass (SIMS), time-of-flight SIMS, sputtered neutral mass, glow-discharge optical emission and glow-discharge mass, Auger electron, and Rutherford backscattering spectrometry, by use of scanning Auger electron microscopy, Raman depth profiling, and Raman mapping, as well as by use of elastic recoil detection analysis, grazing-incidence X-ray and electron backscatter diffraction, and grazing-incidence X-ray fluorescence analysis. The Cu(In,Ga)Se2 thin films used for the present comparison were produced during the same identical deposition run and exhibit thicknesses of about 2 μm. The analysis techniques were compared with respect to their spatial and depth resolutions, measuring speeds, availabilities, and detection limits.

ABSTRACTIn order to transfer the potential for the high efficiencies seen for Cu(In,Ga)Se2 (CIGSe) thin films from co‐evaporation processes to cheaper large‐scale deposition techniques, a more intricate understanding of the CIGSe growth process for high‐quality material is required. Hence, the growth mechanism for chalcopyrite‐type thin films when varying the Cu content during a multi‐stage deposition process is studied. Break‐off experiments help to understand the intermediate growth stages of the thin‐film formation. The film structure and morphology are studied by X‐ray diffraction and scanning electron microscopy. The different phases at the film surface are identified by Raman spectroscopy. Depth‐resolved compositional analysis is carried out via glow discharge optical emission spectrometry. The experimental results imply an affinity of Na for material phases with a Cu‐poor composition, affirming a possible interaction of sodium with Cu vacancies mainly via In(Ga)Cu antisite defects. An efficiency of 12.7% for vacancy compound‐based devices is obtained. Copyright © 2011 John Wiley & Sons, Ltd.

Gas pressure waves in both argon and helium direct current (dc) pulsed glow discharge (PGD) in a Grimm-type source were found and studied with an inserted microphone. First and second harmonics of pressure vibrations were found to be in good agreement with the resonant frequency (2.7 kHz) of the discharge cell. Formation of the gas pressure wave takes place during about 150 µs in edges of PGD. Significant influence of pressure changes on the plasma parameters such as electrical current and optical emission was found. Possible mechanisms responsible for the generation of pressure waves are discussed. In future studies, the results presented here should be taken into account, e.g. for discharge optimization, diagnostics, plasma simulations and corresponding plasma-analytical setups.

The energy transfer to the discharge gas due to various collision processes in the plasma and the heating of the sample are widely known effects in glow discharge (GD) spectroscopy. Despite of the considerable thermal effects and their serious influence on the performance of GD devices, measurements of the discharge gas and sample temperatures are not common at all. The gas temperature depends on the power absorption of the discharge as well as on the temperature of boundaries (sample and anode). In this work the influence of different anode materials in a Grimm-type source on the voltage–current characteristics, crater shapes and GD spectra is investigated. Anodes made of titanium and copper alloys, graphite, and steel with thermal conductivities covering a wide range of values are used. For a fixed voltage and pressure a decrease of the measured current is observed for bad thermal conductive anodes. Cooling of the sample results in an increase of the measured current. Both observations can be explained by changes of the discharge gas temperature. The temperature of the sample is measured from the back side and compared for different anodes. Further, it is found that the choice of the anode material (i) has no significant influence on the crater shape, (ii) results in slightly different sputtering rates and (iii) strong differences of the GD spectra.