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Tribology letters 71(1), 2 (2023). doi:10.1007/s11249-022-01663-7, Published by Springer Science Business Media B.V., Dordrecht

The goal of this work is to evaluate the potential of diamond-like carbon (DLC) coatings on thermoplastic polymers for friction and wear reduction in highly stressed rolling–sliding contacts. Therefore, hydrogen-containing DLC coatings were deposited on the polymer surface by a low-temperature high power pulsed magnetron sputtering (HPPMS) physical vapor deposition (PVD) process. The rolling-sliding contact between coated polyamide 66 (PA66) or coated polyether ether ketone (PEEK) against case-hardened steel 16MnCr5 is investigated in a twin-disk tribometer at normal loads up to FN = 1,000 N, sum velocities between 1 m/s ≤ vΣ ≤ 16 m/s and slip ratios up to s = 50%. Results show a friction reduction with the application of DLC on the considered polymers compared to uncoated polymers under specific lubrication conditions. High solid losses caused by the polymer’s internal damping properties dominate the temperature behavior of the polymer, even when coated with DLC. Regarding the wear behavior, DLC coatings show potential especially under severe mixed lubrication conditions with high-solid load portion and sliding. The knowledge gained about coated polymers can be used to improve the overall tribological performance in terms of friction and wear of thermoplastic machine elements like gears.

For most thin film structures, by changing the wavelength range to fit ellipsometric spectra, the values of the fitted parameters also change to a certain extent. The reason is that compared with the ellipsometric sensitivity many thin films are vertically non-uniform. In absorbing films with significant dispersion in the used wavelength range, the penetration depth of probing light can show large variations depending on the wavelength. Consequently, the value of a fitted parameter for a certain wavelength range is a weighted sum of structural information over different depth ranges corresponding to the different wavelengths. By changing the wavelength range, the range of penetration depths can be adjusted, and the fitted values can be plotted as a function of the probed depth range calculated directly from the determined or tabulated extinction coefficients. We demonstrate the results on deposited polycrystalline thin films. The advantage of this approach over the parameterization of structural properties as a function of depth is that the wavelength scan approach requires no parameterized depth distribution model for the vertical dependence of a layer property. The difference of the wavelength scan method and the vertical parameterization method is similar to the difference between the point-by-point and the parameterized dielectric function methods over the used wavelength range. The lateral structures strongly influence the ellipsometric response, as well. One of the most remarkable effects is when the lateral feature sizes approach the wavelength of the probing light. In this case the effective medium method is not valid any more, since scattering and depolarization occurs. By scanning the wavelength range, the limit wavelength of the onset of scattering can be found, and used for the determination of the corresponding critical lateral period length.

Direct, shuttle-free uptake of extracellular, cathode-derived electrons has been postulated as a novel mechanism of electron metabolism in some prokaryotes that may also be involved in syntrophic electron transport between two microorganisms. Experimental proof for direct uptake of cathodic electrons has been mostly indirect and has been based on the absence of detectable concentrations of molecular hydrogen. However, hydrogen can be formed as a transient intermediate abiotically at low cathodic potentials (

The complex refractive index and the layer thickness of nanocrystalline diamond films was determined by ex situ variable angle spectroscopic ellipsometry in the wavelength range of 191–1690 nm. During the layer depositions argon, methane and hydrogen gases were used as source gases. The combined effect of argon addition and substrate bias was investigated in the microwave plasma assisted chemical vapor deposition of diamond. Multilayer optical models were constructed for the evaluation of the measured ellipsometric spectra. The effective medium approximation and the Lorentz dispersion relation were employed for the modeling of the optical properties of the diamond films.

Ion implantation proved to be a universal technique for producing waveguides in most optical materials. Tellurite glasses are good hosts of rare-earth elements for the development of fibre and integrated optical amplifiers and lasers covering all the main telecommunication bands. Er 3+ -doped tellurite glasses are good candidates for the fabrication of broadband amplifiers in wavelength division multiplexing around 1.55 μm, as they exhibit large stimulated cross sections and broad emission bandwidth. Fabrication of channel waveguides in such a material via N + ion implantation was reported recently. Sillenite type Bismuth Germanate (BGO) crystals are good nonlinear optical materials. Parameters of waveguide fabrication in both materials via implantation of MeV-energy N + ions were optimized. First single-energy implantations at 3.5 MeV at various fluences were applied. Waveguide operation up to 1.5 μm was observed in both materials. Then double-energy implantations at a fixed upper energy of 3.5 MeV and lower energies between 2.5 and 3.1 MeV were performed to suppress leaky modes by increasing barrier width. Improvement of waveguide characteristics was found by m-line spectroscopy and spectroscopic ellipsometry.

Soft error rates in silicon-on-insulator (SOI) static random access memories (SRAMs) with a technology node of 90 nm have been investigated by beryllium and carbon ion probes. The soft error rates induced by beryllium and carbon probes started to increase with probe energies of 5.0 and 8.5 MeV, in which probes slightly penetrated the over-layer, and were saturated with energies at and above 7.0 and 9.0 MeV, in which the generated charge in the SOI body was more than the critical charge. The soft error rates in the SOI SRAMs by various ion probes were also compared with the generated charge in the SOI body. The soft error rates induced by hydrogen and helium ion probes were 1–2 orders of magnitude lower than those by beryllium, carbon and oxygen ion probes. The soft error rates depend not only on the generated charge in the SOI body but also on the incident ion species.

Three dimensional nanostructures fabricated by electron beam (EB) induced deposition were measured by time of flight (TOF) Rutherford backscattering spectrometry (RBS) for checking the spatial resolution of a three dimensional analysis. Pt peaks in TOF-RBS spectra for Pt stripes under a SiO2 layer on a Si substrate samples were slightly shifted to slower position with increasing the thicknesses of the SiO2 layer. The atomic thicknesses for SiO2 fabricated by EB induced deposition measured by TOF-RBS were approximately 25% of the physical thicknesses obtained by a scanning electron microscope. Because SiO2 fabricated by EB induced deposition was not a pure SiO2 layer. The depth resolution in the three dimensional analysis with the TOF-RBS was approximately 10 nm for SiO2 layer. Embedded Ga stripes under a SiO2 layer and Pt stripes on a Si substrate were observed by TOF-RBS. The in-plane resolution under the SiO2 layer was at least less than 70 nm in the three dimensional analysis with the TOF-RBS.

A time of flight (TOF) elastic recoil detection analysis (ERDA) with a toroidal electrostatic analyzer (TEA) using 100 keV Ar+ probe was developed for B profiling in a Si substrate with low energy ion implantation for shrunk semiconductor devices. In the original ERDA, Bohr energy straggling at a stopping foil affects an energy resolution. Thus, in this study, a flight time from the sample to the TEA detector was used for a mass separation in ERDA without the stopping foil. A beam incident angle normal to the sample and a recoil scattering angle were 75° and 50°, respectively. The samples were Si substrates with and without B+ implantation at 2 keV with a dose of 1.5 × 1016/cm2. A boron depth profile was calculated from the difference of the ERDA spectra with TEA for the Si samples with and without B+ implantation. The recoiled B+ and Si+ signals were well separated in the TOF-ERDA spectra for B+ implanted Si with TEA applied voltages of 0.45 to 1.13 kV. The TOF-ERDA spectra with TEA applied voltages of 0.45 to 3.44 kV were converted to the ERDA spectra for B+ and Si+. The B segregation at the surface was observed in both B depth profile calculated from the decrease in the Si yield by ERDA and the ERDA spectrum for B+ converted from the TOF-ERDA spectra. Copyright © 2012 John Wiley & Sons, Ltd.

Optical properties of nanocrystalline and ultrananocrystalline diamond films were studied by ex situ variable angle spectroscopic ellipsometry. The films were prepared by Microwave Plasma Enhanced Chemical Vapor Deposition method. In the experiments Ar, CH 4 , and H 2 gases were used as source gases. Elastic recoil detection analysis was applied to measure the hydrogen content of the deposited layers. Three-layer optical models were constructed for the evaluation of the measured ellipsometric spectra. Besides the Cauchy relation, the effective medium approximation and the Tauc–Lorentz dispersion relation were also used for the modeling of the optical properties of the diamond films. Atomic force microscopy was applied to investigate the surface roughness in function of the deposition conditions.

The optical properties of ion implantation induced disorder in SiC have been investigated in the photon energy range of 5–9 eV using spectroscopic ellipsometry (SE). The most characteristic interband transitions of SiC are located between 5 and 8 eV. This photon energy region is extremely important for the sensitive characterization of lattice order in SiC. The dielectric function of the disordered layer has been calculated taking into account the surface overlayer consisting of oxide and roughness using complementary characterization tools. The dielectric function of the damaged region has been analyzed using different techniques like second derivative analysis and effective medium approximation (EMA) based on reference dielectric functions. The disorder determined by SE has been verified by Rutherford backscattering spectrometry combined with channelling (RBS/C). Using derivative lineshape analysis combined with simulations, the track size can be estimated. The results can give insight into the effect of the decreasing characteristic size of the unchanged crystalline regions on the optical properties. We created near-surface damage using heavy ions, since the penetration depth of light at photon energies around the direct interband transitions is very small (in the range of 10 nm). We used 100-keV Xe at fluences ranging from a slight damage to full amorphization (between 2.0 × 1013 cm− 2 and 1.6 × 1014 cm− 2).

Flight paths and times of secondary electrons, induced by a focused ion beam, from a sample to a secondary electron detector (SED), were simulated with various shield shapes of a SED for improving the time resolution of time-of-flight Rutherford backscattering spectrometry (TOF-RBS) using the secondary electron signal as a start signal, the results of which were compared with experimental time resolutions of the TOF-RBS measurement. The fluctuation in the flight path and, hence, flight time of the secondary electron deteriorates the time resolution of TOF-RBS. The simulated flight time differences for SEDs with or without a shield were 4.4–41 ns with a shield and 1.0 ns without a shield, respectively, indicating that the SED without the shield would improve the time resolution of the single event TOF-RBS. The time resolutions of TOF-RBS using 150 keV Be+ for Au/Si sample with SEDs with and without a shield were 5.6–9.2 and 4.4 ns, respectively. The improved time resolution for SEDs without the shield was confirmed experimentally.

A novel approach was applied to stimulate biodegradation of chloroethenes bya coupled bioelectro-process. In a flow-through column system, microbial dechlorination of tetrachloroethene to cis-dichloroethene, vinyl chloride, and ethene was stimulated by hydrogen produced by water electrolysis. Dechlorinating bacteria (Dehalococcoides spp. and Desulfitobacterium spp.) and also methanogens and homoacetogens were detected in the anaerobic column. Simultaneously, oxidative biodegradation of lower chlorinated metabolites (vinyl chloride) was stimulated by electrolytic oxygen formation in the corresponding aerobic column. The process was stable for more than 100 days and an average removal of approximately 23 micromol/d PCE and 72 micromo/d vinyl chloride was obtained with a current density of 0.05 mA/cm2. Abiotic electrochemical degradation of the contaminants was not observed. Microbial dechlorination correlated with the current densities in the applied range of 0.01-0.05 mA/cm2. The results are promising for environmental applications, since with electrolysis hydrogen and oxygen can be supplied continuously to chloroethene degrading microorganisms, and the supply rates can be easily controlled by adjusting the electric current.

The use of electro-bioremediation has gained increasing interest during recent years. In these hybrid technologies bioremediation is stimulated by electrochemical or electrokinetic techniques to increase pollutant biodegradation efficiency. It is a pre-requisite for successful application of the bio-electro-processes that the microorganisms are not negatively affected by the electric fields or electrode reactions. In this study, for the first time microbial activity of aerobic vinyl chloride (VC) degrading microorganisms was assessed after exposure to constant currents ranging from 0.04 to 14 mA cm −2 . Viability and degradation kinetics were monitored during electrolysis for 4 h using two different types of electrodes: stainless steel and dimensionally stable electrodes (DSA). When the mixed microbial culture was exposed in the electrode compartments, inhibiting effects were observed with stainless steel and DSA electrodes beyond doses of 100 and 50 kJ/L, respectively. Incubation of the VC degrading microorganisms in the mineral medium that was pretreated in the electrode compartments with similar doses, resulted in slower VC degradation kinetics thus demonstrating that the inhibition was due to electrochemical reaction products. When electrodes were separated from the microorganisms by bipolar membranes, no inhibition by the electric field was observed.

Zn and Pb ions were implanted at 100 keV into silicon, in order to form amorphous layers. Ion beam induced epitaxial crystallization of the amorphous silicon was induced at 400 °C using 3 MeV Si+ ion beam. Rutherford Backscattering Spectrometry and channeling techniques were applied to assess the complete amorphization and to follow the epitaxial crystallization and the redistribution of the Zn and Pb atoms. Spectroscopic ellipsometry measurements were performed to determine the thickness of the surface oxide layer and that of the amorphous silicon layers. The evaluation of the ellipsometry data was done using the Tauc–Lorentz model for description of the complex dielectric function of the amorphous silicon. A dose of 3 MeV Si+ ion beam was sufficient for almost complete recrystallization of the ion implantation amorphized silicon layer.

Niobium oxide films were prepared by radio frequency sputtering using Nb 2 O 5 crystalline powder. The thickness and the complex dielectric functions of the as-prepared films were determined by spectroscopic ellipsometry using the Tauc–Lorentz oscillator model. The as-deposited films were amorphous, their refractive index varies between 2.26 and 2.30 at wavelength of 550 nm and the optical band gap varies between 3.29 and 3.46 eV depending on the sputtering conditions. The composition of the layers was studied using Rutherford backscattering spectrometry with 2 MeV 4 He + ion beam. The Nb/O ratio was found in the close vicinity of the stoichiometric one. The films contained small amount of argon. Annealing in air (500 °C, 24 h) causes crystallization and changes in the refractive index and in the extinction coefficient of the film. The optical properties of the sputtered films were compared with those of layers prepared by plasma enhanced chemical vapor deposition, reactive dc sputtering and low frequency magnetron sputtering in other laboratories.

Leichtfluchtige chlorierte Kohlenwasserstoffe (LCKW) sind die haufigsten Schadstoffe an Altlast-Standorten. Ein biologischer Abbau von LCKW ist grundsatzlich moglich, unterliegt im Feld allerdings limitierenden Bedingungen durch einen Mangel an Auxiliarsubstraten und Elektronenakzeptoren. Ziel der Untersuchungen war die Entwicklung eines kombinierten biologischen und elektrochemischen Sanierungsverfahrens, bei dem die Wasserelektrolyse zur Stimulation des biologischen Abbaus genutzt wird. Die Ergebnisse zeigen, dass der elektrolytisch produzierte Wasserstoff und Sauerstoff von den Mikroorganismen direkt fur einen reduktiven bzw. oxidativen Schadstoffabbau genutzt werden kann. Die Auswahl des Elektrodenmaterials ist wesentlich fur die erfolgreiche Anwendung des Bio-Elektro-Verfahrens, da mit Nebenreaktionen an den Elektroden wie z. B. Korrosion gerechnet werden muss. Die Effizienz der mikrobiologischen Dechlorierung kann durch Variation der angewandten Stromdichten gezielt gesteuert werden. Die erforderlichen geringen Stromdichten von 0,05 – 0,1 mA/cm2 ermoglichen niedrige Betriebskosten. Mit einer sequentiellen Elektrodenanordnung wurden in durchstromten Saulen mit feldnahen Schadstoffkonzentrationen Abbauleistungen von 100 % erreicht.

It is known from earlier publications that SiC crystallites grow at the interface of a Si/SiO2 system during heat treatment in CO containing ambient. First 100 nm thick SiO2 layers were thermally grown on Si substrates. The Si/SiO2 structures were heat treated in CO containing atmosphere for 20 and 102 hours at 1190 oC for investigation. Spectroellipsometry was applied to study the microstructure of the heat-treated samples. We assumed a layer at the Si/SiO2 interface that contains crystalline Si and crystalline SiC. After 20 and 102 hour annealing the layer thickness extracted from evaluation of ellipsometric data was 15 nm and 25 nm, the volume fraction of SiC was 38% and 89%, respectively. To confirm the results of the ellipsometry characterization we applied ion beam analysis and X-ray photoelectron spectroscopy. For determination of the carbon content a 4He+ ion beam of 3.5 MeV was selected to take advantage of the scattering cross section of carbon at 165o detection angle is about six times larger than the Rutherford type one. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Bulk single-crystal CdTe, sputter-deposited polycrystalline CdTe films of about 2.5 micron thickness, and single-crystal Si (c-Si) have been ion implanted using 350 keV Xe at fluences ranging from 1×1013 to 16×1013 cm–2 so as to create disorder in a controlled way from fully single-crystalline to fully amorphous material. The general purpose of the investigations is to seek a parameterization of the critical point structures and establish a database for fitting the optical properties of CdTe films having different unknown grain sizes whereby the grain size will be described in terms of an effective defect density. The polycrystalline CdTe samples were magnetron sputtered onto c-Si followed by CdCl2 and Br2-methanol treatment to improve properties in terms of grain size and surface smoothness, respectively. The fluences for use in the ion implantation of CdTe were estimated using the SRIM (Stopping and Range of Ions in Matter) software, and cross-checked by simultaneous implantation of bulk c-Si samples. The optical properties were characterized by second derivative analysis and by a generalized critical point model. Although the damage created by 350 keV Xe in the simultaneously implanted c-Si samples, as measured by both spectroscopic ellipsometry and Rutherford backscattering/ channeling spectrometry (RBS/C), agrees well with the expectations based on the SRIM simulation, the damage created in CdTe remains at a very low level even for doses several times higher than the amorphization level estimated by simulation. The character of the dechanneling of the RBS/C spectra indicates extended defects (presumably dislocation loops). This effect was similar in both single-crystal and thin film polycrystalline CdTe, although less pronounced in thin film samples. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Shallow boron implantation is a widely used step in the Si technology. Boron being a light element, standard RBS and channeling is hardly used for investigating its depth distribution and lattice location after implantation and subsequent annealing. An old idea, the pulled anodic oxidation is applied to create bevelled sample surface in order to explore the implanted boron profile. Detailed description of the special sample preparation method is given. RBS and channeling studies in combination with the 11 B(p,α) 8 Be nuclear reaction at around 660 keV were used to measure the total boron concentration step-by-step both on random direction and channeled samples. Boron profiles extracted from step-by-step nuclear reaction measurements is presented.

A new time-of-flight Rutherford backscattering spectroscopy (TOF-RBS) system with two circular microchannel plates (MCPs) installed at a distance of 140 mm from a sample holder and a scattering angle of 125° and a 100 kV focused ion beam column having a liquid metal ion source (LMIS) of AuSiBe alloy has been assembled to obtain high counting rate and enhanced mass resolution. The possible influence of the two MCPs by logical summation of the output signals on the time resolution was investigated by measuring dedicated thin deposited metallic samples. And, the time resolution was found in the range of 1.5–2 ns.

Indirect optical methods like ellipsometry or scatterometry require an optical model to calculate the response of the system, and to fit the parameters in order to minimize the difference between the calculated and measured values. The most common problem of optical modeling is that the measured structures and materials turn out to be more complex in reality than the simplified optical models used as first attempts to fit the measurement. The complexity of the optical models can be increased by introducing additional parameters, if they (1) are physically relevant, (2) improve the fit quality, (3) don't correlate with other parameters. The sensitivity of the parameters can be determined by mathematical analysis, but the accuracy has to be validated by reference methods. In this work some modeling and verification aspects of ellipsometry and optical scatterometry will be discussed and shown for a range of materials (semiconductors, dielectrics, composite materials), structures (damage and porosity profiles, gratings and other photonic structures, surface roughness) and cross-checking methods (atomic force microscopy, electron microscopy, x-ray diffraction, ion beam analysis). The high-sensitivity, high-throughput, in situ or in line capabilities of the optical methods will be demonstrated by different applications.

Dielectric function of disorder in single-crystalline silicon (c-Si) implanted by He with energy of 40 keV and fluences from 1 × 10 16 to 1 × 10 17 cm −2 were determined around the E 1 and E 2 critical points (CPs) by spectroscopic ellipsometry. The implanted material was modeled by an effective medium composition of c-Si and damaged Si. The dielectric function of damaged Si was calculated using the model dielectric function of Adachi to fit the E 1 and E 2 CP parameters of the MDF. The penetration depth of light in the photon energy range of 3–5 eV is less than 100 nm, which allows a simple layer structure of (surface oxide)/(surface amorphous layer)/(c-Si + damaged Si as a substrate). The oscillator energies and strengths decrease, while the broadening parameters increase with increasing fluence. Rutherford backscattering spectrometry was used for cross-checking of the surface disorder.

Porous silicon layers (PSLs) were prepared by electrochemical etching of p-type single-crystalline silicon (c-Si) wafers having different dopant concentrations to obtain systematically changing sizes of nanocrystals (walls). The microstructure of the porous material was characterized using spectroscopic ellipsometry with multi-layer effective medium approximation (EMA) models. The dielectric function of PSL is conventionally calculated using EMA mixtures of c-Si and voids. The porosity is described by the concentration of voids. Some PSL structures can be described only by adding fine-grained polycrystalline silicon (nc-Si) reference material to the EMA model. Modified model dielectric functions (MDF) of c-Si have been shown to fit composite materials containing nanocrystalline regions, either by fitting only the broadening parameter or also other parameters of the parametric oscillator in MDF. The broadening parameter correlates with the long-range order in the crystalline material, and, as a consequence, with the size of nanocrystals. EMA and MDF models were used to describe systematically changing nanostructure of PSLs. Volume fraction of nc-Si in EMA and broadening parameter in MDF provide information on the nanocrystal size. The longer-term goal of this work is to provide a method for the quantitative characterization of nanocrystal size using quick, sensitive and non-destructive optical techniques.

Metal-organic chemical vapor deposition (MOCVD) made layers of strontium–bismuth–tantalate (SBT) were characterized by spectroscopic ellipsometry (SE) using the Adachi model [S. Adachi, Phys. Rev. B 35 (1987) 7454–7463]. The evaluated optical parameters were correlated with the physical and chemical behavior examined by X-ray diffraction (XRD). As a result, it was possible to fit the measured spectra with the Adachi model in a wide range covering the region of the band gap. The Adachi model provides electronic layer parameters like the transition energy E 0 and broadening Γ . Our investigations established a correlation between XRD-determined average grain size and the electronic layer parameters.

Amorphous carbon nitride (CNx) films were prepared by KrF excimer laser ablation of a graphite target in a nitrogen atmosphere in the inverse PLD geometry. From the ellipsometric point of view, the challenging properties of these films were their exponentially decaying thickness as a function of distance from the ablation source, accompanied by a laterally varying chemical composition and structure. Optical models were developed to accurately describe the dependence of film properties on distance from the ablation, layer thickness, and nitrogen pressure. Multi-layer models were used to characterize the surface roughness as well as lateral inhomogeneities. Multiple angles of incidence and multiple wavelengths were applied in the ranges of 66–72° and 250–1000 nm, respectively. A microspot capability of the spectroscopic ellipsometer (with a spot size of about 100 μm) was exploited to decrease the error caused by the lateral inhomogeneity within the measurement spot. Material properties were derived using the empirical Cauchy dispersion model as well as the Tauc–Lorentz parametric dielectric function model. These models allowed the quantitative determination of the band gap and the oscillator parameters in addition to the layer thicknesses and dielectric functions.

In order to extract the physical properties from an ellipsometric measurement, an optical model of the sample has to be assumed first, because the theory of ellipsometry consists on one-directional computation only (there is no reverse function). Then, the ellipsometric evaluation is an iterative optimising procedure with high time consumption feature and the reliability depends strongly on the a-priori information. The faster the computers are today, the more exactly the physical properties of either the sample or the process can be evaluated. However, the increasing number of the parameters and so, the dimensions of the search space leads to a combinatorial explosion. In the case of larger search space is needed (either less a-priori information is available or more parameters are used), the error surface of the parameter space can be quite “hilly” and may contain even numerous local minima. In the lack of precise a-priori information the Levenberg–Marquardt (LM) gradient search is generally started out of the decreasing area of the global minimum and therefore, it is inappropriate to find the solution. Therefore, there is a hard need of more complex evaluating strategies, which combines the algorithms to make the evaluation more reliable. Different point selection strategies, an extended criteria function and combined algorithms were applied on porous silicon multi-layer and polycrystalline measurements to demonstrate a higher convergence speed (effectiveness) and more reliability.

HfxSiyO1−x−y layers with thicknesses of 2 and 10 nm were measured by medium energy ion scattering (MEIS) with a toroidal electrostatic analyzer (TEA), in which the yield of MEIS spectra was found to decrease with decreasing energy in contrast to conventional Rutherford backscattering spectrometry (RBS), due to the increase in neutralized particles. The HfxSiyO1−x−y spectra obtained by MEIS were corrected with a ratio of the simulated MEIS yield to measured yield for a virgin Si at each energy. The corrected HfxSiyO1−x−y spectra were analyzed and the compositions for 2 and 10 nm thick HfxSiyO1−x−y were obtained by MEIS. An interface layer was found to exist between the Si substrate and the HfxSiyO1−x−y layer.

Ultra shallow dopant profiles of arsenic implanted into Si with an energy range from 0.5 to 3 keV to a dose of 8 × 1014 ions/cm2 with and without spike annealing were measured by medium energy ion scattering (MEIS) with a toroidal electrostatic analyzer (TEA). A shift of the peak of arsenic profile to the surface after spike annealing was observed by MEIS measurement. Most of the implanted arsenic atoms were trapped in the native oxide layer after spike annealing. A recovery of silicon crystal defects induced by arsenic implantation was observed after spike annealing by glancing angle Rutherford back scattering (RBS) measurement with a solid-state detector. The thickness of disordered Si layers down to 1.5 nm was evaluated from glancing angle RBS measurements for implanted sample before and after spike annealing.

500 keV nitrogen implantations at different tilt angles (0o, 0.5o, 1.2o, 1.6o, 4o) with respect to the c-axis of 6H-SiC were carried out. Radiation damage distributions have been investigated by Backscattering Spectrometry combined with channeling technique (BS/C) using 3550 keV 4He+ ion beam. A comparative simultaneous evaluation of the damage depth distributions in the Si and C sublattices of 6H-SiC led to a correction factor of 0.8 in the electronic stopping power of 4He+ ions along channel. Full-cascade Crystal-TRIM simulations with the same set of damage accumulation model parameters could reconstruct the measured shapes and heights of damage distributions for all implantation tilt angles. Secondary defect generation effects in addition to the primary point defect accumulation were assumed in the analysis.

The damage created by implantation of Al ions into single crystalline 4H-SiC has been analyzed using a combination of ion beam techniques and spectroscopic ellipsometry. The samples were implanted at room temperature with 150 keV Al + ions in the fluence range of 4 × 10 14 cm −2 to 2 × 10 15 cm −2 with current densities of 0.4 and 2.5 μA cm −2 . In order to study simultaneously the depth distribution of the disorder produced in both the carbon and silicon sublattice, we used 3.5 MeV He beam in channeling geometry. In this condition the cross-section for carbon is enhanced by a factor of ∼6. The structural recovery of the samples after a further high temperature annealing has been studied. These results have been compared with the optical properties of the samples measured by spectroscopic ellipsometry.

Medium energy ion scattering (MEIS) combining a toroidal electrostatic analyzer with an energy resolution (dE/E) of 4 × 10−3 has been used for ultra-shallow depth profiling of As implanted into Si at 1, 2 and 5 keV to a dose of 1.2 × 1015 ions/cm2 before and after spike annealing at 1075 °C. Depth profiling results extracted from MEIS spectra were compared with those of simulation and SIMS measurement. The arsenic re-distribution close to the surface after spike annealing was found by MEIS and SIMS measurements.

Results are presented of a study of the inverse problem of ellipsometry. In the lack of inverse equations, iterative methods (search) are needed to find the optimal parameters (global minimum) of the adaptive optical model. Different kinds of optical models and search strategies are demonstrated and compared for evaluating real ellipsometric measurements. It is also demonstrated that the well-known gradient search alone is useless if the search space is large (few a-priori information) or the error surface is hilly. The applied algorithms were built in a software, which is freely available at polgaro@mfa.kfki.hu.

Since ion implantation-caused damage changes the complex refractive index of SiC significantly, optical methods can be used to measure the sample properties sensitively, non-destructively and quickly. In the present work the damage created by ion implantation into SiC and its change upon annealing was characterized by spectroscopic ellipsometry (SE). 4H SiC samples were implanted with 150 keV Al using doses between 4×l0 14 and 2×l0 15 cm −2 with current densities from 0.4 to 2.5 μA cm −2 . They were subsequently annealed at 1100 °C in Ar for 1 h. SE measurements were made before and after annealing. The relative damage was measured using the Bruggeman effective medium approximation combining the dielectric function of single-crystalline and totally amorphized SiC. Therefore, the prerequisite of the proper interpretation of SE data measured on partially damaged SiC is the knowledge of the complex dielectric function of single-crystalline and completely ion implantation amorphized SiC. The complex dielectric function of ion implantation-amorphized SiC was determined from a high-dose implant. Different optical models and the influence of experimental conditions on the damage were investigated. The results were crosschecked by Rutherford backscattering spectrometry.

100 keV Ar and Xe ions, as well as 40 and 60 keV Ge ions were implanted at room temperature into single-crystalline silicon. The used doses covered the range from slightly damaged to totally amorphized layers for the Xe, Ar and Ge ions, respectively. The relative damage was characterized using spectroscopic ellipsometry (SE) with the Bruggeman effective medium approximation combining the dielectric function of single-crystalline and ion implantation-amorphized silicon. The depth distribution of damage was described by the coupled half-Gaussian model and with an improved model, which describes the damage profile using sublayers with thicknesses inversely proportional to the slope of the profile. The SE results were cross-checked using Rutherford backscattering spectrometry (RBS). The damage peaks were determined from the SE and RBS measurements for different ions and different doses ranging from slight damage to total damage. Comparing the damage peaks (caused by the same doses) determined with SE and RBS, a systematic deviation can be observed: SE measures more damage than RBS for lower and less damage than RBS for higher doses.

Plasma immersion ion implantation (PIII) exploits the basic advantages of ion implantation using the simplest equipment, direct extraction of ions from a plasma and implantation into a surface. In the present study comparative investigations were performed using high-depth-resolution Rutherford backscattering, cross-sectional transmission electron microscopy and spectroscopic ellipsometry to analyze the composition of the topmost layer and to investigate structural modification caused by PIII in single crystalline silicon.

Reductive dehalogenases play a critical role in the microbial detoxification of aquifers contaminated with chloroethenes and chlorethanes by catalyzing the reductive elimination of a halogen. We report here the first heterologous production of vinyl chloride reductase VcrA from Dehalococcoides mccartyi strain VS. Heterologously expressed VcrA was reconstituted to its active form by addition of hydroxocobalamin/adenosylcobalamin, Fe(3+), and sulfide in the presence of mercaptoethanol. The kinetic properties of reconstituted VcrA catalyzing vinyl chloride reduction with Ti(III)-citrate as reductant and methyl viologen as mediator were similar to those obtained previously for VcrA as isolated from D. mccartyi strain VS. VcrA was also found to catalyze a novel reaction, the environmentally important dihaloelimination of 1,2-dichloroethane to ethene. Electron paramagnetic resonance (EPR) spectroscopic studies with reconstituted VcrA in the presence of mercaptoethanol revealed the presence of Cob(II)alamin. Addition of Ti(III)-citrate resulted in the appearance of a new signal characteristic of a reduced [4Fe-4S] cluster and the disappearance of the Cob(II)alamin signal. UV-vis absorption spectroscopy of Ti(III)citrate-treated samples revealed the formation of two new absorption maxima characteristic of Cob(I)alamin. No evidence for the presence of a [3Fe-4S] cluster was found. We postulate that during the reaction cycle of VcrA, a reduced [4Fe-4S] cluster reduces Co(II) to Co(I) of the enzyme-bound cobalamin. Vinyl chloride reduction to ethene would be initiated when Cob(I)alamin transfers an electron to the substrate, generating a vinyl radical as a potential reaction intermediate.

Polysilicon/thin oxide/single-crystalline silicon structures used as emitters of bipolar transistors were measured using spectroscopic ellipsometry. The thin SiOx layer was deposited on the substrate in a rapid thermal processing chamber, then polysilicon was deposited, implanted with As, and annealed. During annealing the SiOx layer dissolves to islands retarding the diffusion of As, which results in a shallow p-n junction. The process—and as a consequence, the device performance—depends sensitively on the thickness of the oxide layer. We developed optical models to measure the thickness of the SiOx layer at each process step, i.e., after SiOx deposition, after polysilicon deposition, and after annealing. The structure, the surface quality, and the homogeneity of the polysilicon layers were obtained from the same optical model. The thickness of the initially 0.76–0.86 nm SiOx layer decreased to the detection limit of about 0.2 nm during annealing, together with a significant crystallization of the deposi...

Optical, compositional, and structural properties of strontium bismuth tantalate (SBT) films deposited in a high throughput low-pressure chemical vapor deposition reactor using liquid metal-organic precursors were characterized using three non-destructive techniques, spectroscopic ellipsometry (SE), Rutherford backscattering spectrometry (RBS), and X-ray diffraction (XRD). The thicknesses and the refractive indices of the SBT layers were calculated with SE using different parametric dielectric function models. The samples were characterized with RBS using different tilt angles and probe ions to enhance the depth resolution and the mass separation. Comparison with SE measurements supports the results of Bahng et al. revealing an increasing refractive index (n) with increasing Bi/Sr ratio. The decreasing grain size measured by XRD was reflected as a decrease of n in the SE measurement. We show that RBS, XRD, and SE supply a wide range of information about the SBT layers, which can be used for qualification as well as for feedback to layer production. The results suggest that by SE, being used as in situ or in line characterization tool, the control of even complex MOCVD deposition looks feasible.