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Analytical and Bioanalytical Chemistry (v.358, #1-2)

9th Applied Surface Analysis Workshop (AOFA 9) Aachen, 24–27 June, 1996 by H. Lüth; J. Rottmann (pp. 1-2).

Surface analysis by nondestructive testing techniques by M. Kröning; F. Häußler; W. Arnold (pp. 3-9).

Nondestructive testing (NDT) goes beyond the determination of geometrical, physical, and chemical as well as technological parameters. In addition to this, measuring results are compared with predetermined values so that quality features can be tested. Specific NDT-methods suitable for surface analysis like eddy current testing, Barkhausen noise measurements, ultrasonics, and atomic force microscopy are discussed. Furthermore, the contrast mechanisms, the resolution and their application in NDT are presented.

Optical spectroscopy for in situ characterisation of semiconductor interfaces and layers by Dietrich R. T. Zahn (pp. 10-14).

The potential of optical techniques for semiconductor interfaces and growing layers is demonstrated using in particular the example of Raman spectroscopy in combination with molecular beam epitaxial (MBE) growth. Recent developments allow this method to be applied not only in situ but while growth progresses. This application critically depends on the resonant excitation which provides the required sensitivity for layers in the nanometre range. Here the heteroepitaxy of II–VI compound semiconductors on III–V substrates serves as an example to illustrate the wealth of information, e.g. on layer composition, crystallinity, growth rate, and interfacial reactivity. Very recent results on gallium nitride growth clearly reveal that such experiments can be performed even at temperatures as high as 685 °C.

Electron energy loss spectroscopy and its application in material science by Angela Rizzi (pp. 15-24).

The physical processes underlying the inelastic scattering of electrons on passing through a solid as well as on travelling outside a solid in the vicinity of a surface are briefly reviewed. Image energy filtering in a Transmission Electron Microscope (EFTEM) for elemental mapping and High Resolution Electron Energy Loss Spectroscopy (HREELS) for the characterization of semiconductor surfaces and layered structures are discussed as representative applications of Electron Energy Loss Spectroscopy (EELS) in material science, with main emphasis on semiconductors.

Quantitative depth profiling of thin layers by K. Wetzig; S. Baunack; V. Hoffmann; S. Oswald; F. Präßler (pp. 25-31).

Foundations of sputtering profile evaluation are discussed, which allow the conversion of a measured sputtering profile, I = f(t), to a true element concentration profile c_elem. = f(z), or in special cases to a phase profile c_phase = f(z). As a relatively new method for quantitative thin film analysis, glow discharge optical emission spectrometry (GDOES) has the special advantage of a narrow depth resolution function. Growing sputter crater profiles can be eliminated by a deconvolution algorithm, as is shown for TiN/TiAlN multilayers. The sputtering rate as a function of depth may be also deduced by a special wedge crater profile, which is sputtered into the material by an ion beam under suitable beam control. Further information on a phase depth profiling may be obtained by principal component analysis, as is discussed for AES and XPS investigations of P implanted Ti. A special technique of cross section imaging of thin layers is the analytical TEM, which allows the parallel investigation of microstructure and element distribution, as illustrated for a Cr-Fe multilayer.

Identification of ultra-thin layers by cross-sectional Raman spectroscopy by T. Werninghaus; A. Schneider; D. Drews; D. R. T. Zahn (pp. 32-35).

Micro-Raman spectroscopy measurements in a cross-sectional sample geometry were performed for three heterosystems (3C-SiC/Si(100), diamond/Si(100), and ZnS_xSe_1-x/GaAs(100)). Using an automated xy-stage with a minimum step width of 100 nm one-dimensional scans across the interface were taken. It is demonstrated that sufficient sensitivity for the detection of ultra-thin layers with thicknesses in the nanometer range can be achieved. Thus surface and interface layers not accessible in a plane-view geometry can be identified. In addition, the depth-resolved variation of sample properties like interfacial reactions, stress, and stoichiometry will be discussed.

Different techniques for determining the coating weight of phosphate layers on galvanized steel by means of FT-IR-spectrometry by K. Molt; D. Behmer; M. Pohl (pp. 36-41).

The determination of the weight per unit area (“coating weight”) of phosphate layers on galvanized steel by means of FT-IR-spectrometry has been performed by three different techniques: (i) principal component regression (PCR) of absorption data, (ii) utilizing the thickness dependent wavenumber shift of a band due to a special optical surface effect observed with parallel-polarized radiation and (iii) of an interference band observed with perpendicular-polarized radiation.

On the quantification of SNMS analyses of silicate glasses and oxide coatings by R. Schmitz; G. H. Frischat; H. Paulus; K.-H. Müller (pp. 42-46).

The new high frequency mode (HFM) of the SNMS apparatus, type INA3, is especially suited for the analysis of electrically non-conducting materials. Experiments were carried out with glasses and various oxide coatings in order to demonstrate the quantifiability of HFM analyses with respect to these materials. The influence of the composition of the samples and the selected parameters of the HFM, such as accelerating voltage, duty cycle and frequency, on the quantifiability of the measurements are discussed. It is shown that quantification is possible within certain limits of composition.

Comparative studies of SIMS and SNMS analyses during the build up of sputter equilibrium under oxygen and rare gas ion bombardment by U. Breuer; H. Holzbrecher; M. Gastel; J. S. Becker; H.-J. Dietze (pp. 47-50).

Sputtering of solid surfaces by using a focused ion beam is the basis for secondary ion mass spectrometry (SIMS) and sputtered neutral mass spectrometry (SNMS). The ion bombardment initiates not only redistribution of sample atoms but also massive changes in the surface and near surface composition of the bombarded area due to the sputter process and implantation of the primary ions. Changes in the matrix-composition affects the secondary ion yields and therefore a steady state (sputter equilibrium) has to be reached before SIMS data can give quantifiable results. SNMS is much less affected by those yield effects and therefore a combination of SIMS and SNMS can establish a basis for interpretation of SIMS data before the steady state is reached. In order to determine the effects of primary ion incorporation, we applied different primary ion species successively to generate different equilibria. An oxygen ion beam oxidizes the sample surface and by using a rare gas primary ion (PI) this oxide can be removed and analyzed.

Development and applications of a new IR-radiation heating in thermal desorption mass spectrometry TDMS by H. Paulus; M. Lammers; G. Venema; K.-H. Müller; J. Scholz; H. Züchner (pp. 51-53).

An infra-red radiation heating was developed for applications in thermal desorption mass spectrometry (TDMS), avoiding disadvantages of the various types of sample heatings used so far. In a first application D₂-desorption profiles were determined from deuterium doped vanadium samples. Thereby a linear relationship could be found between the amount of detected deuterium and known D-concentrations. D₂-desorption profiles from D doped Si showed 2 maxima corresponding to different desorption processes. In another application characteristic TD mass spectra were obtained for a solvent agent of an adhesive. The further investigation of the desorption behaviour of a specific fragment yielded a relationship between the detected amount of this species and the adhesive strengths of polycarbonate foils.

Nanoscale characterization of semiconductor surfaces by spatially resolved photocurrent measurements by R. Hiesgen; Dieter Meissner (pp. 54-58).

A method based on scanning tunneling microscopy has been developed to measure spatially resolved primary photocurrents together with the topographical image. As model semiconductors n- and p-type WSe₂-monocrystals have been used. The system consisting of metal tip, gap and semiconductor sample behaves as a classical metal-insulator-semiconductor (MIS) solar cell. The resolution achieved in the photocurrent image is at least 1 nm. In order to demonstrate the technique, the surfaces of clean n- and p-type WSe₂ samples have been investigated. The method has been extended to analyze metal modified semiconductor surfaces and some of these results are shown here.

Characterization of the interdiffusion in Au-Al layers by RBS by A. Markwitz; N. Vandesteene; M. Waldschmidt; G. Demortier (pp. 59-63).

The non-destructive standardless nuclear analysis technique Rutherford Backscattering Spectroscopy (RBS) is used to study interdiffusion phenomena in aluminium and gold layers with a high depth resolution, e.g., at the interfaces. A multilayered system consisting of alternate aluminium and gold layers was deposited under high vacuum conditions on polished glassy carbon and single-crystalline silicon substrates to investigate the interdiffusion of gold and aluminium in as-deposited layers. The characteristic peaks of gold and aluminium are in background-free regions of the RBS spectra if the layers are sufficiently thin and substrates like silicon with a low Z are used. The RBS results indicate that the Au-Al interdiffusion behaviour in as-deposited layers strongly depend on the conditions during deposition in the evaporation chamber.

Interface analysis of noble dental casting alloys by B. Reusch; J. Geis-Gerstorfer; C. Ziegler (pp. 64-66).

Surface analytical methods such as scanning electron microscopy (SEM), electron dispersive X-ray analysis (EDX), and X-ray photoelectron spectroscopy (XPS) were used to study the surface properties of several noble metal casting alloys which are used as core materials for fixed prosthodontics. In particular surface morphology, surface segregation, and oxide formation were studied as the key parameters influencing the adhesion properties between alloy and ceramic veneer.

XPS, SIMS and SNMS applied to a combined analysis of aerosol particles from a region of considerable air pollution in the upper Rhine valley by F. Faude; J. Goschnick (pp. 67-72).

The water acceptance of aerosol particle surfaces is a key factor for atmospheric hygiene as it initiates gravitational settling by water up-take. To examine the concurrent influences on the surface of real airborne particles concerning the deposition of hydrophobic organic material, six particle sampling campaigns were performed in polluted outdoor-air under different air conditions. The particles were examined with SNMS, SIMS, and XPS with special view of the chemical inventory of the surface region. The total elemental inventory obtained with SNMS shows carbon compounds in all particle size classes. Soot seems to govern the submicron particles while the coarse fraction contains soil dust or fly ash. Depth-resolved analysis shows organic carbon compounds to be surface-enriched and to dominate the composition of the topmost molecular layers of the particles independent of the collection time and particle sizes. However, chlorides and ammonium sulfate were also found at the surface which will always reduce the hydrophobicity of the surface caused by organic compounds. No correlation was discovered between the ozone or NO₂ concentration of the air and the type and quantity of the organic surface components.

Scanning Reactance Microscopy on organic materials by F. Müller; A.-D. Müller; M. Hietschold (pp. 73-76).

Two types of modulation techniques based on Scanning Tunneling Microscopy (STM) were used to image the material contrasts of a plasma-polymer gold composite surface. The modulation of the tunneling voltage gives information on the complex local surface conductivity and the modulation of the tip sample distance allows the determination of work function and capacitance variations. Furthermore, calculations are presented.

A combined ultrahigh vacuum scanning tunneling-scanning electron microscope system by U. Hodel; U. Memmert; U. Hartmann (pp. 77-79).

A combined ultrahigh vacuum scanning tunneling-scanning electron microscope system is presented. This system allows to approach arbitrary locations on a sample within a range of 5 mm × 5 mm under electron microscopic control. The usefulness of this system is demonstrated by the characterization of a 1 μm wide photolithographically produced Ag microbridge on a Si(100) substrate.

In-situ investigations on the SILAR-growth of ZnS films as studied by tapping mode atomic force microscopy by R. Resch; G. Friedbacher; M. Grasserbauer; T. Kanniainen; S. Lindroos; M. Leskelä; L. Niinistö (pp. 80-84).

Tapping mode atomic force microscopy (TM-AFM) has been successfully used for in-situ imaging of the deposition of ZnS films with the successive ionic layer adsorption and reaction (SILAR) method. The films were deposited in-situ using the commercial TM-AFM liquid cell as a flow-through reactor. The potential of TM-AFM has been used to study the growth of ZnS on different substrates up to 50 SILAR cycles. Reactants and rinsing water were alternately exchanged in the cell by a computer controlled valve system. In comparison to earlier work performed with the conventional AFM operated in contact mode, imaging artefacts introduced by lateral shear forces can be largely eliminated with TM-AFM. On glass the roughness is observed to decrease initially until typical island formation takes place at a larger number of deposition cycles. On mica island formation can be observed right from the beginning of the process and the roughness increases with increasing number of deposition cycles.

Interface characterization of PICVD-coated polymer substrates by V. Rupertus; K. Berresheim; C. Ottermann; S. Thiel; M. Kopnarski; K. Bange (pp. 85-88).

The binding structure in the interface region oxide film/polymer has been investigated by means of XPS and is correlated with the adhesion obtained by a Pull Test. Polycarbonate (PC) and diethyleneglycol-bisallylcarbonate (CR39) are employed as substrate and SiO_xC_yH_z-films are deposited by using a pulsed microwave plasma deposition process (PICVD). Best adhesion is obtained by pretreatment of the substrate surface with an O₂-plasma which increases the O/C ratio, in combination with a PICVD-process with low precursor content.

X-ray absorption spectroscopy (NEXAFS) of polymer surfaces by W. E. S. Unger; A. Lippitz; C. Wöll; W. Heckmann (pp. 89-92).

The application of X-ray absorption spectroscopy (NEXAFS) in surface analysis of polymers is demonstrated by means of selected examples. High resolution NEXAFS spectra of poly(ethylene), poly(butadiene) and poly(styrene) are presented. The effect of oxygen plasma treatment on the surface of polypropylene foils was investigated. It is shown that angle resolved NEXAFS spectroscopy can be used to observe preferential orientations of segments of macromolecules at the surface of a poly(ethylene terephthalate) foil. Finally, the formation of a polymer-metal interface was observed in a model study of chromium evaporated onto a poly(bisphenol-A-carbonate) film surface. NEXAFS spectroscopy and XPS are complementary tools in surface analysis of polymers. NEXAFS polymer spectra can be used in parallel electron energy loss spectroscopy (PEELS) to control for electron beam damage.

Molecular weight determination of bulk polymer surfaces by static secondary ion mass spectrometry by K. Reihs; M. Voetz; M. Kruft; D. Wolany; A. Benninghoven (pp. 93-95).

The determination of molecular weights at surfaces of bulk polymer materials can be accomplished by static secondary ion mass spectrometry (SIMS) via fragments originating from repeat units and end groups. The intensity ratio of these fragments depends on the polymer chain length as seen for bisphenol-A-polycarbonate and perfluorinated polyethers (Krytox). A kinetic model of fragment ion formation explains the molecular weight dependent fragment intensities and links them to properties of the molecular weight distribution. In the most simple case one obtains the number average molecular weight n> at the surface. This technique can be used for the determination of the molecular weight at bulk polymer surfaces such as a CD-ROM made from polycarbonate by injection molding.

Preparation and characterization of thin TiO2-films on gold/mica by J.-D. Grunwaldt; U. Göbel; A. Baiker (pp. 96-100).

Flat and highly (111) oriented gold and silver films were prepared by physical vapour deposition (PVD) using optimized deposition parameters. On these films, which were characterized with atomic force microscopy (AFM), scanning tunneling microscopy (STM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), titanium dioxide films were deposited by electron beam evaporation and dip coating. Dip coating from titanium tetraisopropoxide solutions resulted in films with different morphology and coverage depending on the alkoxide concentration (0.009 mol/L – 0.60 mol/L) and the post-treatment. Scanning electron microscopy (SEM) and AFM revealed that the deposited TiO₂ consists of amorphous, highly porous islands when the applied alkoxide concentration is high (0.05 mol/L – 0.6 mol/L). At higher temperatures these amorphous TiO₂ islands sintered significantly and crystallized to anatase. In contrast, transparent TiO₂ films were obtained from low concentrated alkoxide solutions (< 0.01 mol/L) which covered the whole substrate, similar to electron beam evaporated thin films. Sputter profiles with ion scattering spectroscopy (ISS) indicated that the film thickness is in the range of 2 nm when alkoxide solutions with a concentration of 9 mmol/L are used. The deposition of TiO₂ by electron beam evaporation normally resulted in significantly reduced TiO₂ films, completely oxidized ones were obtained when deposition was performed at elevated oxygen partial pressures (p(O₂) > 2 × 10^–5 mbar).

Optimization of III/V binary growth with RHEED in MOMBE by C. Ungermanns; M. v. d. Ahe; R. Carius; A. Förster; M. Hollfelder; H. Hardtdegen; M. Matt; K. Nicoll; R. Schmidt; B. Setzer; H. Lüth (pp. 101-104).

In this paper we report on the optimization of homoepitaxial InAs and InP growth in MOMBE (metalorganic molecular beam epitaxy). A correlation is made between good optical quality material and the observation of RHEED (reflection high energy electron diffraction) intensity oscillations. It will be shown, that in situ RHEED oscillations can be used to determine a growth parameter window in MOMBE.

Electron microscopic characterization of SrTiO3 films obtained by anodic spark deposition by F. Schlottig; D. Dietrich; J. Schreckenbach; G. Marx (pp. 105-107).

Crystalline strontium titanate layers were deposited on titanium anodes from Sr(OH)₂aqueous electrolyte solutions by a plasmachemical-electrochemical process of anodic spark deposition. X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) have been used to study the properties of the polycrystalline material. Strontium titanate was deposited on the titanium anode surface as a ceramic layer from an aqueous electrolyte. The typical pore structure morphology of the anodic spark deposit (ASD) was characterized by SEM as well as fractures which provide an intimate contact between layer and substrate. XRD-study showed that the layers are composed of a mixture of SrTiO₃ and TiO₂.

Self assembled molecular monolayers on oxidized inhomogeneous aluminum surfaces by C. Bram; C. Jung; M. Stratmann (pp. 108-111).

The adsorption and self organization of phosphonic acids on oxidized aluminum surfaces has been investigated by surface sensible techniques: ARXPS, AES and FTIR. The analysis has been performed on Al 99.999 samples and on surfaces of a technical alloy whose surfaces contain iron inclusions. The results obtained lead to the conclusion that self organization is not only possible on perfect defect free surfaces but also on inhomogeneous ones.

XPS-investigations on laser-modified Si3N4 ceramics by S. Oswald; P. Burck (pp. 112-115).

For the ultimate use of micro machining in technology, the interaction of laser light and silicon nitride ceramic have been studied. Using X-ray photoelectron spectroscopy (XPS), different effects generated by radiation from Nd:YAG (free running mode) and excimer lasers have been observed. With the Nd:YAG laser (λ = 1.06 μm), reaction zone depths of several 100 nm, apparently caused by melting, were found. The excimer laser treatment with a lower penetration depth of the light (λ = 248 nm) led to very low chemical surface damage. Thus the excimer laser is favored for exact micro machining of nitride ceramics.

3D-Atom-probe study of oxygen-adsorption on stepped platinum surfaces by W. Tieber; W. Athenstaedt; M. Leisch (pp. 116-118).

Oxygen adsorbed on Pt (011), (012) and (113) has been studied by means of field desorption in a three-dimensional atom-probe. The formal procedure of these experiments is quite similar to thermal desorption. Comprehensive investigations with the thermal desorption technique report on a highly stable atomic oxygen phase on Pt, which has been attributed to a subsurface oxygen layer or platinum oxide. In atom-probe depth profiling experiments oxygen was measured only in the topmost layer. Oxygen and platinum have been detected almost as single atomic ions, Pt-oxygen complexes have not been observed in the time-of-flight mass spectra. The 2D plots of the impact positions of the desorbed ions as well as field ion micrographs show most of the oxygen adsorbed in highly co-ordinated sites on the (012) and (113) planes.

Characterization of thin-film surfaces by fractal geometry by W. Zahn; A. Zösch (pp. 119-121).

The applicability of models based on fractal geometry to characterize thin-film surfaces is investigated. The fractal geometry of sputtered chromium nitride and silicon nitride thin film surfaces is described using Fourier profile analysis of scanning tunneling microscopy images and a box counting method. The CrN_x- and SiN_x-coatings were deposited on silicon wafers by reactive magnetron sputtering. The columnar structure of the amorphous silicon nitride varied with deposition similarly to the stucture of the polycrystalline chromium nitride films. For quantitative comparison of film morphology, an average column diameter has been used as a characteristic. The average column diameter increases with increasing gas pressure because of shadowing processes during deposition. The fractal dimension decreases with increasing pressure. Films with fine columnar structures are characterized by a larger fractal dimension than films with a coarse columnar structure. The fractal dimension determined by Fourier analysis is larger than the dimension calculated by the box counting method. The reason may be the limited pixel density of digitized images.

TEM and SNMS studies on the oxidation behaviour of NiCrAlY-based coatings by D. Clemens; V. R. Vosberg; H. J. Penkalla; U. Breuer; W. J. Quadakkers; H. Nickel (pp. 122-126).

The effect of minor Ti additions content (0% Ti, 0.4% Ti, 1% Ti, 2% Ti) on the oxidation behaviour of Ni-20Cr-10Al-0.4Y (in weight-%) model alloys was investigated in the temperature range 950° C to 1100° C up to 200 h in Ar – 20% O₂. Alloy microstructure, oxide scale morphology and microstructure of the scale were characterized by SEM/EDX and TEM. The growth mechanisms of the alumina scales formed on the model alloys were studied by two-stage oxidation experiments with ¹⁸O₂-tracer and subsequent SNMS-analyses. The microstructural observations were correlated with the oxide scale properties in respect to growth rates and spalling resistance, which was tested during cyclic oxidation.

Stresses in alumina scales on high-temperature alloys measured by X-ray and optical methods by V. R. Vosberg; D. Clemens; M. G. Berger; W. J. Quadakkers; W. Fischer; H. Nickel (pp. 127-130).

The effect of silicon and titanium on the spallation resistance of alumina scales formed on NiCrAlY-type alloys has been investigated using model alloys with different additions of Si or Ti. For this purpose cyclic oxidation experiments were carried out at temperatures between 950 and 1100 °C. For evaluation of the growth and temperature induced stresses in the oxide scales selected samples were analysed by X-ray stress evaluation (XSE) at ambient temperature after various oxidation treatments. The compressive strains in the scales were found to increase with increasing oxidation time, tending to become constant after longer oxidation times. The strains reduced remarkably, when scale damage, such as cracking, started. The developed strains in the oxide scales appeared to be affected by the microstructure of the alloy and the phase distribution in the subsurface depletion layer beneath the oxide. This distribution is affected by the presence of Si and Ti. Apart from the X-ray method, laser Raman spectroscopy (LRS) was calibrated for strain measurement by XSE results aiming at applying this method for stress analysis at higher temperatures.

SNMS depth profiling in oxide scales on Fe-20Cr-5Al alloys by M. Göbel; G. Borchardt; S. Weber; S. Scherrer (pp. 131-134).

In order to investigate transport phenomena during oxide scale growth commonly a two-stage oxidation technique (¹⁶O₂/¹⁸O₂) is used [1–4]. In this contribution, SNMS measurements have been performed on an industrial high temperature alloy after oxidation of the material. The problem of depth calibration in this particular case is examined. It is shown that the variation of the particle density in the scale and in the substrate can be neglected and that only the variation of the sputter yield has to be taken into account. In order to validate this approach two independent techniques have been applied. First, a taper section of the sample has been prepared and a SNMS line scan has been measured. Secondly, thermogravimetric measurements have been performed to determine the scale thickness after each oxidation step.

Characterisation of intermediate layers in hot-dip zinc coated steels by P. Karduck; T. Wirth; H. Pries (pp. 135-140).

The intention of this work is the full characterisation of morphology, composition and structure of so-called intermediate layers in continuously galvanised steel sheets. These layers grow as a reaction product of the sheet with the liquid zinc which contains a few tenth % of mass fraction aluminium. Conventional methods of surface analysis combined with ion sputtering fail to resolve the layers because of extreme surface roughness of the zinc coating induced by the sputter process. Better access to the intermediate zones can be attained after carefully removing the zinc coating by etching or chemical polishing without attacking the layers. The uncovered layers can be analysed by EPMA, AES-line scanning and SEM. Especially an EPMA-thin film analysis technique turns out to be most suitable to analyse quantitatively the composition and stoichiometry of phases in the layer(s). Also layer thicknesses can be determined in terms of mass coverage. The results of these analyses are in good agreement with literature data from metallurgical and constitutional investigations. The applied techniques can be recommended for quality assurance and failure analysis in industrial production of continuously hot-dip zinc coated steel sheets.

Clean and ordered surfaces of CeNi2Ge2 layers on W(110) by B. Schmied; M. Wilhelm; U. Kübler; M. Getzlaff; G. H. Fecher; G. Schönhense (pp. 141-143).

Investigations of the geometric and electronic properties of ternary Ce-based heavy fermion systems CeT₂X₂ (T : Ni,Pd,Rh; X : Ge,Si) were carried out by means of electron spectroscopic methods. The main problem for these surface-sensitive techniques is the preparation of well-ordered and atomically clean surfaces. The ternary substance CeNi₂Ge₂ was grown on a W(110) substrate by MBE with subsequent annealing. A nearly layer-by-layer growth mode was detected using MEED. The annealed layers are ordered, but show small Ni₂Ge crystalline islands. The composition was characterised by means of AES in dependence of the substrate as well as the annealing temperature. Electronic properties are investigated by angle resolved photoelectron spectroscopy.

Practical experiences with electron gun charge-compensation during SIMS-analysis by N. Reger; F. J. Stadermann; H. M. Ortner (pp. 143-145).

Electrical charging during SIMS-analysis (secondary ion mass spectrometry) is a severe limitation for the analysis of non-conductive samples. In most cases this charging can be compensated with the aid of an electron gun. This is an already established method to analyze insulating samples. In this work results of a systematic study of electron gun charge compensation in our CAMECA ims5f ion microprobe are described.

Depth profiling analysis of thick Ni- and Co-doped oxide layers on Cr-based alloys of the interconnector of a solid oxide fuel cell using rf GDMS by A. I. Saprykin; J. S. Becker; U. v. d. Crone; H.-J. Dietze (pp. 145-147).

A radiofrequency glow discharge ion source designed in our laboratory was coupled to a commercial double-focusing mass spectrometer in the original mode with an inductively coupled plasma ion source. This modification of rf GDMS extends the analytical capability of the mass spectrometer with ICP for the analysis of liquids to the direct analysis of insulating, semiconducting and conducting solids in the whole range of conductivity.The analytical procedure of the depth profiling analysis of the oxide coating of chromium-based alloys used as interconnectors in SOFC technology was discussed. The investigation of the depth profiles of Ni and Co in the thick oxide layers on the surface of Ni- and Co-doped alloys showed that the incorporation of these elements into the oxide during oxidation at 950°C is uniform.

Combined use of lattice source interferences and divergent beam X-ray interferences to investigate the microstructure of ion-bombarded Cu-Sn-diffusion zones by S. Däbritz; E. Langer; W. Hauffe (pp. 148-153).

Diffusion processes and phase formations as well as the crystallographic structure of microelectronic contact zones decisively influence the electrical and mechanical properties of electronic components. Using various physical methods in the same analysis area, such as lattice source interferences and divergent beam X-ray interferences, optical microscopy and SEM, electron probe microanalysis and the ion beam slope cutting method, profound statements about the microstructure can be made. A Kossel camera and an additional divergent beam X-ray device were built and installed in a Scanning Electron Microscope (SEM) CamScan CS 44. X-ray interferences in the microrange of selected areas were taken using both systems, providing information on the crystallographic orientation and the real structure of the specimens. The interference techniques were tested using single-crystal and ion-bombarded polycrystalline copper. In addition, applying the mentioned methods, the diffusion generated intermetallic compounds Cu₃Sn, Cu₆Sn₅ and Cu₄₁Sn₁₁ were investigated using ion-bombarded Cu-Sn/Pb model samples.

A new high luminosity UHV orange type magnetic spectrometer used for depth selective Mössbauer spectroscopy by B. Stahl; R. Gellert; G. Klingelhöfer; M. Müller; R. Teucher; E. Kankeleit (pp. 153-155).

A new magnetic spectrometer of the orange type has been built for energies up to 45 keV. Its features are:· Transmission: 20% of 4π· Relative momentum resolution: 0.1 to 1%,· Energy band width: ΔE/E = ± 4%For Auger Electron Spectroscopy (AES) a combination with an electrostatic retardation field around the sample will provide an even higher resolution. For depth selective conversion electron Mössbauer spectroscopy (DCEMS) the exceptional high effective luminosity of the ultrahigh vacuum (UHV) orange spectrometer allows the analysis of non-enriched samples in reasonable time without loss in depth resolution. The UHV was realized by a differentially evacuated double chamber system made of an aluminium alloy using Viton gaskets. The inner part can be heated to 150° C.

Influence of the topography of zinc coated sheet on the results of electron probe microanalysis by P. Busch; Ulrike Förster (pp. 155-159).

As far as possible, electron probe microanalyses (EPMA) must be carried out on optimally smooth surfaces. When analyzing technical surfaces with a roughness resulting from the rolling or coating process, EPMA results are biased, which has consequences especially when determining element mass layer in the detection limit area. This effect was tested and a corrective process was developed on electrolytically galvanized and hot-dip galvanized steel sheet of varying roughness.

Progress in the accuracy enhancement for elemental analysis by quadrupole-based plasma-SNMS by J. Goschnick; M. Sommer; H. J. Ache (pp. 159-162).

The elemental quantification in plasma-based SNMS is hampered by the matrix dependence of the detection efficiencies. The signals of elements of unknown compounds can only be converted to concentrations with mean detection factors resulting in concentrations with an uncertainty mainly given by the matrix effect. This situation can be considerably improved by energy measurements of the sputtered particles. The energy distribution (ED) can be used in two ways. First, the exact knowledge of the ED to each detected element allows an element specific integration of the directly sputtered atoms eliminating thermal species from resputtered wall deposition. For a set of copper compounds the spread of the Cu detection factors could be reduced from ± 63% for the conventional measurement to ± 35% using energy resolved data. Second, the shape of the ED of postionised atoms differs considerably from all interfering species, such as clusters as well as twice charged atoms which could superimpose on the atomic signals. A quantitative shape analysis of the measured ED was developed to correct for these interfering species. Examples are given for both superpositions with cluster intensities and interferences with twice charged intensities. To reduce the additional time necessary to obtain the ED, the number of energy resolved data points was reduced in steps down to 3 points only which still reduced a superposition error to half of the value without ED based correction.

Model electrodes with defined mesoscopic structure by K. A. Friedrich; A. Marmann; U. Stimming; W. Unkauf; R. Vogel (pp. 163-165).

Model electrodes with defined mesoscopic structure were either generated by adsorption of surfactant stabilized metal clusters from colloidal solution on a support of gold or by electrochemical deposition of platinum on gold substrates. Both types of model electrodes were characterized by STM (scanning tunnelling microscopy), cyclic voltammetry and electrooxidation of adsorbed CO. The supported colloidal Pt as well as the electrochemically deposited Pt revealed different reactivities regarding the CO monolayer electrooxidation as compared to a polycrystalline Pt bulk electrode. In addition, in-situ FTIR (Fourier transformed infrared) spectroscopy was applied to characterize CO adsorbed on electrochemically deposited Pt on gold. Combined with the structural information from STM it seems likely that the differences regarding the catalytic properties of the model electrodes are due to different coverages of the substrate with catalyst particles.

Wavelet filtering for analytical data by M. Wolkenstein; H. Hutter; M. Grasserbauer (pp. 165-169).

Some recent results considering the application of non-linear wavelet analysis to signals and data of chemical interest are summarized. In particular the wavelet thresholding algorithm described by Donoho is used for de-noising different analytical signals. Additionally, the effect of wavelet filtering on subsequent signal and image processing methods is investigated. It is shown that wavelet de-noising significantly suppresses noise, while sharp edges and corners remain sharp after processing, and improves subsequent data processing.

Surface composition of PtCo alloys Results of improved thermodynamic calculations incorporating data from a bulk critical state by W. Hofer; L. Z. Mezey (pp. 169-170).

The new approach for the calculation of surface composition profiles of binary alloys (MTCIP-2A: Modern Thermodynamic Calculation of Interface Properties – Second Approximation), applied so far for low-index surfaces of PtNi, PtCo and PtRh, is further improved and applied for PtCo, leading to a better overall agreement with the experimental data, especially in the previously problematic case of Pt₂₅Co₇₅(111). For that, the Gibbsian thermodynamic conditions for critical states and other changes, such as the calculation of surface free energies (used here when improving the description of lattice distortion release), have been included.

3D analysis of solids using sputtered MCs+ ions by Hubert Gnaser (pp. 171-175).

The 3-dimensional characterization of solids by means of secondary-ion mass spectrometry is investigated. Monitoring MCs⁺ molecular ions emitted from surfaces upon Cs⁺ bombardment, laterally-resolved ion images were recorded with acquisition times of typically a few seconds which exhibit a dynamic sensitivity range in excess of 10² and a lateral resolution of about 2–3 μm. A quantitative data evaluation via relative sensitivity factors (RSFs) transforms them into elemental distribution maps. From the applied RSFs, local (i.e. erosion-time dependent) sputtering yields can be derived; together with atomic densities (which might be interpolated from pure-element values) a local depth scale (relative to some reference level) is assigned to each pixel of the 3D data volume recorded during the analysis. In conjunction with the elemental concentration values, this provides the possibility of a complete reconstruction of the 3D sample volume removed by sputtering. This approach is exemplified by means of a laterally inhomogeneous semiconductor test specimen.

C 1s and Au 4f7/2 referenced XPS binding energy data obtained with different aluminium oxides, -hydroxides and -fluorides by O. Böse; E. Kemnitz; A. Lippitz; W. E. S. Unger (pp. 175-179).

A number of partially catalytically active aluminium compounds characterised by powder XRD have been investigated by XPS and XAES using a new method for static charge referencing [1, 2]. In detail, α-Al₂O₃, γ-Al₂O₃, boehmite γ-AlO(OH), bayerite α-Al(OH)₃, hydrargillite γ-Al(OH)₃, α-AlF₃, β-AlF₃, and AlF_2.3(OH)_0.7· H₂O and a hexa-fluoropropylene oxide (HFPO) modified γ-Al₂O₃ are examined. Well defined and chemically inert 20 nm gold particles are deposited as a nearly statistical distribution on the sample surface avoiding large coagulation effects. This procedure allows a determination of gold referenced XPS and XAES data sets. Binding energies (BE) of Al 2p, Al 2s, O 1s and F 1s photoelectron peaks as well as kinetic energies (KE) of Al KLL and F KLL Auger electron emission peaks are presented in relation to the Au 4f_7/2 BE reference. XPS and XAES data found in literature are, in most cases, C 1s referenced and scatter in a broad range. BE differences Δ between the C 1s charge reference BE and Au 4f_7/2 charge reference BE obtained with our samples are monitored by using the Al 2p orbital. These BE differences Δ clearly suggest that the chemical state of carbon observed in this study is not as uniform as required for reliable static charge referencing.

Electrical and optical properties of melting Au/Si eutectics on Si(111) by M. Brüggemann; K. Mümmler; P. Wissmann (pp. 179-181).

The Au/Si system exhibits an extremely low eutectic temperature of 363° C. Thin gold films of 200 nm thickness were deposited on Si(111) single-crystals and the electrical and optical properties of the melting mixtures were investigated. The resistivity measurements were performed in situ in a combined LEED/Auger apparatus. A highly resolving spectroscopic ellipsometer was used for the optical analysis in the wavelength range 400–900 nm. The eutectic temperature was found to be lower than for bulk Au/Si samples. The structure analysis showed that small liquid Au/Si islands embedded in the silicon surface are formed by the melting process. Various heating/ cooling cycles show a characteristic hysteresis behaviour.

Adsorption of triallylamine on Si(111) and its coadsorption with triethylgallium – A combined HREELS and XPS study by D. Freundt; G. Landmesser; A. Rizzi; H. Lüth (pp. 182-186).

The adsorption of triallylamine [(C₃H₅)₃N; TAA] on Si(111)-(7 × 7) under UHV conditions was studied by means of surface sensitive electron spectroscopy. The High-Resolution Electron Energy Loss Spectroscopy (HREELS) yields the spectrum of vibration modes of the adsorbed species. X-ray Photoelectron Spectroscopy (XPS) gives insight into the chemical environment and the relative concentrations in the near surface region. The tertiary amine TAA physisorbes at room temperature without dissociation. Successive annealing steps induce the dissociation of the physisorbed phase at temperatures above 400°C. Further annealing leads to partial desorption of the allyl groups from the surface. At temperatures above 600°C the remaining allyl groups are fully dissociated. Hydrogen leaves the surface and nitrogen and carbon start to diffuse into the substrate. The surface chemistry of triallylamine adsorbed on a heated substrate behaves in a very similar way. The coadsorption of TAA with triethylgallium [(C₂H₅)₃Ga; TEG] in the temperature range between 500 and 800°C induces no significant change of the surface reactions. Only a small amount of gallium could be detected at the surface. The nucleation of GaN has not been observed, neither on Si(111) nor on Al₂O₃(0001) substrates.

Decomposition of methane on polycrystalline thick films of Ga2O3 investigated by thermal desorption spectroscopy with a mass spectrometer by F. Becker; C. Krummel; A. Freiling; M. Fleischer; C. Kohl (pp. 187-189).

Methane in air can be detected by the conductivity increase of Ga₂O₃ films. Films (200 μm) of β-Ga₂O₃ were prepared by depositing a suspension of β-Ga₂O₃ powder (Johnson Matthey; 32102; 99,99%) on alumina substrates. The films were exposed to 20 kPa O₂ for 15 min at 934 K. In thermal desorption spectroscopy (TDS, β = 4,6 K/s, UHV conditions) only O₂ occured at temperatures above 934 K. On reduction in 100 Pa H₂ for 5 min at 800 K, only a suboxide, Ga₂O (above 880 K), indicating a destabilisation of the lattice [1], a broad hydrogen peak (440–930 K) and the formation of water (700–900 K) were observed. No Ga₂O₃ and O₂ were found in desorption. At temperatures between 260 K and 934 K the film was exposed to methane (100 Pa, 5 min). For exposure temperatures between 630 K and 934 K, CO, CO₂, H₂, and small amounts of CH₄ and the suboxide Ga₂O appeared in desorption. A reaction scheme for the decomposition of methane is proposed. It includes the adsorption of CH₄, the dissociation of CH₄, the desorption of H₂O and the formation of oxygen vacancies. These vacancies and the adsorbed hydrogen both acting as donors may explain the conductance increase on exposure to methane observed by other authors.

Surface structural and chemical characterization of Pt/Ru composite electrodes: a combined study by XPS, STM and IR spectroscopy by S. Cramm; K. A. Friedrich; K.-P. Geyzers; U. Stimming; R. Vogel (pp. 189-192).

Electrochemical Ru deposits on Pt(111) surfaces are investigated by STM; the images of the Ru-modified surfaces show islands of monoatomic height and between 2–5 nm in diameter. The density of islands on the surface depends on the Ru deposition potential (observed by STM and XRSD) and the cyclic voltammograms indicate an increasing Ru coverage for lower deposition potentials. The Ru surface coverage is determined by ex-situ XPS measurements and a linear dependence of the Ru coverage on the deposition potential is demonstrated. IR spectra of a monolayer of adsorbed CO on the Ru-modified Pt(111) surfaces show distinct bands for CO adsorbed on Pt and on Ru. For the integrated band intensity of the CO/Ru vibration a linear dependence on deposition potential is found indicating that lateral dipole interactions between CO adsorbed on Pt and Ru are unimportant and that the CO coverage on the Ru islands is constant for the Ru coverages investigated. The possibility of using adsorbate vibrational bands for the determination of the coverage of deposits is discussed.

Cosegregation-induced formation of surface compounds on (110) and (111) oriented surfaces of bcc alloys with 3d and 4d metals by E. C. Viljoen; B. Eltester; C. Uebing (pp. 193-195).

Cosegregation phenomena were studied on the (110) and (111) surfaces of Fe-3.5%Mo-N single crystals by means of Auger electron spectroscopy (AES) and low energy electron diffraction (LEED). On both surface orientations cosegregation of molybdenum and nitrogen was found to cause the formation of two-dimensional MoN surface compounds which are stabilized by strong chemical interactions between the two solutes. The maximum surface coverages of the segregants, which were established at temperatures around 500°C, correspond to less than a full monolayer of the MoN surface compounds. LEED investigations revealed a complex diffraction pattern of the MoN covered (110) alloy surface, while a (1 × 1) structure was observed on the (111) surface. However, no facetting of either surfaces occurred. This finding is in sharp contrast to previous results obtained for ferritic alloys with various 3d metals such as Fe-15%Cr-N and Fe-3%V-C,N. It is concluded that the maximum MoN surface coverage is too small to induce the facetting of the bcc(110) and bcc(111) alloy surfaces.

AES and LEED investigation of Al segregation and oxidation of the (100) face of Fe85Al15 single crystals by B. Eltester; C. Uebing; H. Viefhaus; H. J. Grabke (pp. 196-199).

The surface segregation and oxidation behavior of Fe₈₅Al₁₅(100) were investigated by means of AES and LEED. Sputter cleaning of the surface causes preferential Al removal and leads to an Al depleted surface layer. The segregation of Al to the Fe₈₅Al₁₅(100) surface was studied in the temperature range from 300 to 800°C. At 375 to 400°C a weak c(2 × 2) LEED pattern is found. At temperatures in excess of 600°C thermodynamic equilibrium is approached very rapidly. At such temperatures Al segregation leads to a well-ordered (1 × 1) LEED structure with bright and sharp spots at a low background intensity. Oxidation at room temperature leads to disordered oxygen adsorption, whereas at 700°C a (6 × 6) superstructure is observed in addition to the matrix spots. This superstructure is attributed to the formation of a thin Al₂O₃ overlayer on the Fe₈₅Al₁₅(100) surface.

Chemical stability of (NH4)2S-passivated InP(001) surfaces – investigations by XPS and XPD by H. Peisert; P. Streubel; T. Chassé; R. Szargan (pp. 201-203).

UV/ozone supported surface oxidation of wet chemically cleaned and sulfurized InP(001) was investigated using XPS in order to study the chemical stability of (NH₄)₂S-passivated surfaces. Sulfur coverages of about one monolayer thickness were not sufficient to completely passivate the InP surface against oxidation. Similar oxides of the substrate components were observed at the surfaces. Evidence for surface passivation was found in the chemical stability of incorporated sulfur (In-S bonds), the lower growth rate of the oxide layer and its reduced thickness at comparably large UV/ozone exposures. The oxide layer was found to be amorphous at all stages of the oxidation process, as was proved by X-ray photoelectron diffraction.

SIMS depth profiling of vertical p-channel Si-MOS transistor structures by U. Zastrow; R. Loo; K. Szot; J. Moers; T. Grabolla; D. Behammer; L. Vescan (pp. 203-207).

SIMS depth profiling during O₂ ⁺ bombardment has been performed to analyse epitaxially grown Si p-n-p layers, which define the p-channel region in vertical Si-p MOS transistors, as well as to establish “on-chip” depth profiling of the functional vertical device. The SIMS detection limit of ³¹P in Si, phosphorus used as n-type dopant in the transistor, has been optimised as a function of the residual gas pressure in the SIMS analysis chamber and of the sputter erosion rate. We demonstrate that good vacuum during SIMS analysis combined with high erosion rates allows the simultaneous quantitative SIMS depth profiling of n- and p-type dopant concentrations in the vertical transistor. Small area “on-chip” SIMS depth profiling through the layered structure of Al-contact/TiSi₂/Si(p-n-p)/Si-substrate has been performed. Factors influencing the depth resolution during “on-chip” analysis of the transistor are discussed especially in terms of sputtering induced ripple formation at the erosion crater bottom, which has been imaged with atomic force microscopy.

Depth profile analysis of thin film solar cells using SNMS and SIMS by M. Gastel; U. Breuer; H. Holzbrecher; J. S. Becker; H.-J. Dietze; H. Wagner (pp. 207-210).

SNMS (sputtered neutrals mass spectrometry) and SIMS (secondary ion mass spectrometry) are used for the depth profile analysis of thin film solar cells based on amorphous silicon. In order to enhance depth resolution, model systems are analyzed only representing parts of the layered system. Results concerning the TCO (transparent conducting oxide)/p interface and the n/i interface are presented. To minimize matrix effects, SNMS is used when the sample consists of layers with different matrices. Examples are the TCO/p interface (where the transition lengths of the depth profiles are found to be sharper when ZnO is used as TCO compared to SnO₂) and SnO₂/ZnO interfaces in coated TCO layers (where a Sn contamination inside the ZnO layer is found depending on the plasma pressure during the ZnO deposition). SIMS is used when the limits of detection reached by SNMS are not sufficient. Examples are H depth profiles in ZnO layers or P depth profiles near the n/i-interface.

New insights into the ZnO/a-SiC:H(B) interface using XPS analysis by E. Böhmer; F. Siebke; H. Wagner (pp. 210-213).

A poor electric contact between the ZnO and the p-type a-SiC:H(B) layer limits the fill factor of amorphous silicon solar cells using ZnO as front electrode. To gain a deeper understanding of the chemical and electronic properties of the ZnO/p interface, in-situ XPS measurements were applied to thin a-SiC:H(B) films deposited on ZnO. The effects of H₂ plasma pretreatments on clean ZnO surfaces and the influence of deposition conditions on the ZnO/a-SiC:H interface were investigated. Upon H₂ plasma treatment, a shift of all core levels towards higher binding energies indicates the formation of an accumulation layer. Depth profiling across the ZnO/a-SiC:H interface shows SiO₂ formation on ZnO. The depth profile of the ZnO related core levels exhibits two features: a reduction of the ZnO at the interface and a hydrogen induced accumulation layer in the n-type ZnO. The latter causes a depletion of the p-layer resulting in an enhanced series resistance and diminished fill factor.

Application of RF GDMS for trace element analysis of nonconducting La0.65Sr0.3MnO3 ceramic layers by R. Jäger; J. S. Becker; H.-J. Dietze; J. A. C. Broekaert (pp. 214-217).

Radio-frequency glow discharge mass spectrometry (RF GDMS) has been applied to the determination of trace elements in ceramic perovskite layers (La_0.65Sr_0.3MnO₃) using synthetic standards. For the preparation of these standards high-purity powder of the basic material (La_0.65Sr_0.3MnO₃) was doped with trace elements in concentrations from 20 to 500 μg/g and the mixture was pressed to compact samples. The resulting calibration curves and the calculated relative sensitivity factors (RSF) differed only from 0.4 to 2 for different elements. For nearly all elements the standard deviations in the determination of trace elements in La_0.65Sr_0.3MnO₃ were better than 15% and detection limits (using the 3σ-criterion) were below 10 μg/g. Changes of the discharge parameters (RF power, pressure of the discharge gas (Ar) in the RF glow discharge) have no significant influence on the sensitivity to elements.

Investigation of water diffusion into quartz using ion beam analysis techniques by O. Dersch; A. Zouine; F. Rauch; J. E. Ericson (pp. 217-219).

Diffusion of water into quartz was studied by measuring H and ¹⁸O concentration profiles in surface layers of quartz samples treated hydrothermally in the range of 125° C to 200° C. Sample surfaces were orientated normal to the c-axis. The measurements were performed using the nuclear reactions ¹H(¹⁵N,αγ)¹²C and ¹⁸O(p,α)¹⁵N. The diffusion profiles have widths of up to 500 nm. Diffusion rate constants derived from the profiles are in the range of 10^–15 cm²/s to 10^–18 cm²/s and show a distinct temperature dependence, yielding a rough estimate of about 60 kJ/mole for the activation energy.

Topographical and microanalytical investigation of corrosion processes on the solid material in the system metal-metalloid glassy alloy (Fe,Cr)80(P,C,Si)20, aqueous FeCl3 solution, and air in the region of the “amorphous solid/liquid/air” phase interface by K. Forkel; C. Köcher; E. Schierhorn; K. Adam; F. G. Wihsmann; P. J. M. Bartos (pp. 219-224).

Ribbons of the metal-metalloid glassy alloy (Fe,Cr)₈₀(P,C,Si)₂₀ and Fe₇₅Cr₅P₈C₁₀Si₂, respectively, were treated with an aqueous solution of FeCl₃ (29 mass%) in an ultrasonic bath. The surface of the amorphous solid is maximally influenced at the flux line as the contact zone of glass/solution/ air. This region of the amorphous solid was studied by light microscopy, scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDXA) as well as the electron beam micro analysis (EBMA) after the treatment. Changes in the surface stage and the surface behaviour take place independently of the state of the initial glass surface (shiny or dull side of a ribbon). Reaction products of different morphology were formed. In the flux line of the glass an enrichment of Si and Fe could be detected. These results agree with those of electrochemical measurement. According to this, a chloride ion containing acid aqueous solution is rather corrosive to this glassy alloy.

Plasma SNMS investigations on powder metallurgical Cr and Ti-48Al-2Cr after oxidation in air and 15N2/18O2 atmosphere by H. Jenett; J. D. Sunderkötter; M. F. Stroosnijder (pp. 225-229).

Oxidation experiments at 800°C and 900°C, partly in atmospheres enriched in isotope tracers, with subsequent SNMS depth profiling confirmed that two well-known oxidation mechanisms are also valid for the title materials: In powder metallurgical Cr, Y addition shows the reactive element effect, most completely by means of Y implantation and to a lesser extent by the addition of Y₂O₃ dispersion, classical fast Cr outward transport dominated kinetics is replaced by kinetics that is governed by slow inward diffusion of oxygen. In γ-TiAl with 2 at-% Cr, N is identified as the “frontline” oxidizing element being able to penetrate existing oxide and nitride layers inward towards the bulk metal. These results exemplify that the combination of plasma SNMS depth profiling with oxidation experiments, especially in ¹⁵N₂/¹⁸O₂ tracer atmosphere, and with reactive element implantation is an excellent method to obtain basic insights into corrosion mechanisms. Especially advantageous is the use of SNMS because of its much lesser matrix dependence compared to SIMS which has more frequently been used for this kind of experiments.

Oxidation behavior of mechanically alloyed chromium based alloys by U. v. d. Crone; M. Hänsel; W. J. Quadakkers; R. Vaßen (pp. 230-232).

The oxidation of chromium and chromium based alloys with yttria additions of 0.5 to 4 wt.%, processed by mechanical alloying, was investigated. Additionally, the effect of milling time on the oxidation behavior was examined. The samples were oxidized at 950°C in air. Weight changes, optical microscopy and SEM were utilized to characterize the oxidation behavior. Although it appeared that the presence of yttria reduced the oxidation rates significantly, the exact concentration of yttria was far less essential for the oxidation properties than the yttria distribution.Therefore the oxidation resistance of ODS (oxide dispersion strengthened) alloys strongly depends on the exact manufacturing process.

Investigation of the synthesis and internal structure of protective oxide layers on high-purity chromium with SIMS scanning techniques by C. Brunner; H. Hutter; K. Piplits; P. Wilhartitz; R. Stroosnijder; M. Grasserbauer (pp. 233-236).

The major problem affecting the application of chromium in high temperature processes is the ongoing spallation of the protective oxide layer formed during hot-gas oxidation. This results in a continuous material erosion. To gain a deeper insight in the spallation and oxidation process, a high-purity powder-metallurgically produced chromium sample was submitted to a two-stage hot gas oxidation process. The formed oxide layers were investigated by 3D SIMS and scanning SIMS. The formation of the protective oxide layer is carried by the diffusion of chromium from the bulk through the already existing oxide layer and the reaction of the diffused chromium with the oxygen from the gaseous phase. In parallel to the growing of the oxide layer, an accumulation of impurities at the interface oxide layer – bulk can be observed. The enrichment of trace elements at the interface level (for the investigated sample Cl and N) can be explained by the low solubility of these elements in chromium oxide and therefore their inability to diffuse through the already formed protective layer.

Experiments on the analysis of thick, non-conductive metallic oxide layers on sheet using HF-SNMS by D. Sommer; Alfons Essing; Herbert Patotzki (pp. 236-239).

First experiments are described for depth profile analytical characterization of non-conducting enamel layers using secondary neutral particle mass spectrometry (SNMS) with HF sputtering technology. The homogeneous distribution of the oxidic components in the enamel layer are examined. The considerable layer thicknesses (> 80 μm) mean that the direct application of HF-SNMS for assessing interface and adhesion mechanisms is not practical at present. To prepare the interface layer from the steel side, the use of different preparation techniques is shown to abrade the sample with simple metallographic techniques down to a residual steel thickness of approx. 1–5 μm.

Characterization of chemically modified silica by infrared and solid state nuclear magnetic resonance spectroscopy by K. Heger; G. Marx; E. Brendler; B. Thomas (pp. 240-241).

Silica modified with benzene was investigated by infrared and solid state ¹³C cross-polarization magic angle spinning nuclear magnetic resonance spectroscopy (¹³C CP MAS NMR). Whereas infrared spectroscopy did not allow to distinguish between phenyl and polyphenyl groups, this was possible by solid state nuclear magnetic resonance spectroscopy.

Characterization of SiO2 protective coatings on polycarbonate by S. Jakobs; Ulrike Schulz; Angela Duparré; Norbert Kaiser (pp. 242-244).

SiO₂ protective coatings have been deposited on polycarbonate substrates by plasma ion assisted deposition. The influence of ion energy on the water permeability and the surface topography of the coatings was studied by infrared spectroscopy and atomic force microscopy. Coatings deposited at sufficiently high ion energies show a barrier effect against moisture uptake and considerably reduced film roughness. Both effects are attributed to an increase of the packing densities of the coatings.

Flow sorption calorimetry, a powerful tool to investigate the acid-base character of organic polymer surfaces by S. Schneider; F. Simon; D. Pleul; H.-J. Jacobasch (pp. 244-247).

Flow sorption calorimetry (FSC) can be a useful tool to estimate the Lewis acid-base behaviour of the surface of organic polymers with less than 1 m²/g surface area. Polyethylene powders grafted with different amounts of acrylic acid have been chosen as samples. The surface of the powders was investigated by means of X-ray photoelectron spectroscopy (XPS) at first and than brought into contact with the strong electron donor triethylamine in a special FSC measuring system. The heat of the displacement isotherm together with the surface excess isotherm of triethylamine adsorbed onto the powders was determined. The results obtained with FSC and XPS were well correlated and gave a comprehensive picture of the acidic surface character of modified polyethylene.

Chemical analysis of the interface between Al thin films and polymer surfaces pretreated with KrF-excimer laser radiation by D. A. Wesner; R. Weichenhain; W. Pfleging; H. Horn; E. W. Kreutz (pp. 248-250).

KrF-excimer laser irradiation of polyimide (PI) and polybutylene terephthalate (PBT) at fluences near and below the material removal threshold ɛ_t causes oxygen depletion, with the effect being much more pronounced for PI. In the case of PI there is also a slight nitrogen depletion, an opening of the imide ring at the N atom, and the formation of doubly bonded nitrogen, probably in an isoimide structure. Aluminium films on PI exhibit significantly more interfacial Al³⁺ after irradiation near ɛ_t, indicating an enhancement of the metal/polymer binding, in spite of the reduced oxygen content in such surfaces. In contrast, irradiated PBT surfaces show little change in the amount of interfacial aluminium species compared to unirradiated surfaces.

Surface analysis of polyethyleneterephthalate by ESCA and TOF-SIMS by F.-R. Lang; Y. Pitton; H. J. Mathieu; D. Landolt; E. M. Moser (pp. 251-254).

PET (poly(ethylene-terephthalate)) samples provided by different suppliers were investigated with the surface-sensitive methods as electron spectroscopy for chemical analysis (ESCA) and time-of-flight secondary ion mass spectrometry (TOF-SIMS). Analysis by means of ESCA provides chemical information from a near-surface region of roughly 6 nm. Specific ESCA data on chemical shifts and on the ratio between oxygen and carbon are compared with corresponding values expected for the molecular structure of bulk PET. In addition, direct chemical information on the molecular structure at the PET surface (essentially from the first two monolayers) has been obtained by TOF-SIMS. Especially, positive and negative TOF-SIMS mass spectra were analyzed in detail and assigned with respect to characteristic polymer fragment ions. Several polymer additives as well as some contaminations present at the PET surfaces could be identified with TOF-SIMS. Dependent on the PET supplier, antioxidants and lubricants such as Irgafos 168, octylstearate, octylpalmitate, octylarachidate and PDMS (polydimethylsiloxane) found at the sample surfaces give typical positive and negative ion fragments.

Characterisation of pure or coated metal surfaces with streaming potential measurements by C. Bellmann; A. Opfermann; H.-J. Jacobasch; H.-J. Adler (pp. 255-258).

In the field of corrosion prevention, the characterisation of metal surfaces is useful to obtain information about the necessary preparation of the surface and about the quality of thin coatings of coupling and protective agents. Electrokinetic measurements can be used to determine the properties of modified polymer surfaces, metal sheets, and different surface preparations. However, it was necessary first to create special conditions for measuring the streaming potential, such as electrical isolation of the sample sheets together with the use of inert systems, as shown by the example of aluminium. According to the usual procedure the metal was first coated with a thin layer of a coupling agent. The effect of this adhesive agent depends on the degree of its adsorption by the metal surface. The quality of this layer can be characterised by streaming potential measurements, which can show the degree of coverage, the adhesive strength of the coated layer, and the effective chemical properties of the treated surface. These results were confirmed by wetting measurements. The production of surfaces which allow us to couple a coating varnish to the adhesive agent in good quality was demonstrated.

Characterization of vapor phase deposited organic molecules on silicon surfaces by S. Dieckhoff; R. Höper; V. Schlett; T. Gesang; W. Possart; O.-D. Hennemann; J. Günster; V. Kempter (pp. 258-262).

Thin films of 2,4,6-tris-(2,2-bisphenyl-propane)-1,3,5-triazine (p-CPC trimer), deposited on clean, oxidized and H₂O-saturated Si(100) surfaces, have been investigated by X-ray Photoelectron Spectroscopy (XPS), Ultraviolet Photoelectron Spectroscopy (UPS), Metastable Impact Electron Spectroscopy (MIES) and Atomic Force Microscopy (AFM). The spectroscopic results indicate a preferential molecular orientation due to the interaction of the trioxytriazine rings with the substrate surfaces. The study of the surface topography during film formation exhibits characteristic two dimensional domain patterns caused by a selforganization process.

Characterisation of adsorbed layers on sulphide minerals by photoelectron spectroscopy by A. Schaufuß; P. Roßbach; I. Uhlig; R. Szargan (pp. 262-265).

The systems galena/2-mercaptobenzothiazole (MBT) and pyrite/MBT have been studied using synchrotron radiation excited photoelectron spectroscopy (SRXPS). The chemisorption of MBT and the multilayer formation of 2,2′-dithiobis(benzothiazole) (BBTD) are evidenced by additional structures, observed beside the substrate signals, in the S2p-spectra of cleaved mineral surfaces after adsorption of MBT. The amount of the complex remains constant at concentrations as high as 10^–5 mol/L whereas the amount of BBTD increases. From the dependence of the adsorbate intensities on the excitation energy the conclusion can be drawn that an overlayer of BBTD on a chemisorbed layer of MBT is formed. The very weak adsorption of MBT on pyrite in alkaline solutions may explain the selective flotation of galena from pyrite in alkaline media.

ESCA-Analysis of tin compounds on the surface of hydroxyapatite by Karin Schenk-Meuser; H. Duschner (pp. 265-267).

The formation of tin compounds on the surface of hydroxyapatite, the main crystalline component of teeth, is discussed controversially. SnF₂ is used as an anticaries agent in toothpaste preparations. Pure hydroxyapatite (HAP) is treated with extracts of commercially available toothpastes containing tin fluoride and analyzed by electron spectroscopy (ESCA). Survey spectra and depth profiles are recorded. The chemical shifts measured for the HAP samples are compared with those of standard tin compounds. It is concluded that on the surface of hydroxyapatite a mixture of two-valent fluoro-phosphato compounds is formed. SnO is not found in the mixture.

Investigation of aerosol particles by atomic force microscopy by G. Köllensperger; G. Friedbacher; M. Grasserbauer; L. Dorffner (pp. 268-273).

AFM has been applied for studying morphology and size distribution of nanometer-sized particles adsorbed on flat surfaces. In order to optimize imaging of these ultrafine particles different substrates were evaluated with respect to their roughness and stability under the influence of the sensing tip. Moreover, a method for calculating particle volumes from the three-dimensional AFM data is described. This greatly enhances the information content of AFM images, because a large number of particles in the raw data can be evaluated automatically in order to derive information on size distribution or surface coverage. This evaluation method has also been applied successfully to quantitatively describe changes on particles induced by different humidity of the surrounding atmosphere.

Examination of organosilicon impregnating mixtures by static SIMS and diffuse reflectance FT-IR by C. Bruchertseifer; K. Stoppek-Langner; J. Grobe; M. Deimel; A. Benninghoven (pp. 273-274).

Results of an extensive examination concerning effectiveness and durability of two different commercial organosilicon impregnating mixtures applied to Obernkirchener sandstone are presented briefly. Hygric tests and contact angle measurements prior to spectroscopic surface investigations of a propyl/octylsilane mixture and a methyl/octylsiloxane mixture reveal different long-term stability of the protective organosilicon coatings. General surface characteristics of the coatings were elucidated by time-of-flight secondary ion mass spectrometry (TOF-SIMS). The measurements on freshly soaked stone slabs give evidence of spherical silsesquioxanes and their homoderivatives only of the precursor compound with the shorter alkyl chain. Investigations on the weathered coatings (8 years) show the presence of silsesquioxanes only in case of the silane system. Additional DRIFT (diffuse reflectance FT-IR) measurements on both freshly soaked and exposed material confirm the presence of the coating in case of the silane mixture, but not in case of the siloxane mixture.

Low energy ion bombardment of Ti and TiNx films by C. Eggs; H. Wulff; R. Hippler (pp. 275-277).

The influence of low energy ion bombardment on TiN_x film growth and film properties was investigated. The discharge was characterized using Langmuir probe technique as well as energy resolved mass spectrometry with a plasma monitor (Hiden HAL 301 S/EQP). The deposited films were investigated by means of X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). Increasing the N₂ gas flow as well as increasing the negative substrate voltage at constant gas flow effect an increase of the N/Ti ratio in the films determined by XPS. The influence of the energy flux to the surface due to ion bombardment was mainly recognized in the substructure of the films. In addition, pure Ti films were modified by nitrogen ion bombardment after deposition using an ion gun. An increase of the N/Ti ratio was observed with increasing ion energy. Finally saturation is reached.

Examination of wear mechanisms of hard coatings by T. Niebuhr; H. Bubert; H.-D. Steffens; D. Haumann; K. Kauder; U. Dämgen (pp. 278-280).

PVD-CrN and -TiN coatings are abraded in a wear test equipment which simulates the sliding-rolling friction of a screw rotor used in screw compressors. The coatings show significant differences concerning their durabilities. The worn-out coatings as well as the debris particles produced by abrasion are analyzed by means of X-ray induced photoelectron spectroscopy and Auger electron spectroscopy. The failure mechanism of TiN coatings can be explained by spalling off small debris particles, whereas the failure mechanism of CrN coatings has to be attributed to tribooxidation, because in this case the analyzed particles exclusively consist of chromium oxide. Nevertheless, CrN coatings show the lowest wear rate. When changing the environment (inert atmosphere or water lubrication) in the test equipment, the tribooxidation of CrN can be reduced or totally stopped, but a decrease in wear rate cannot be achieved. In this case tribooxidation leads to a better wear resistance.

Scratch test measurement of tribological hard coatings in practice by G. Berg; C. Friedrich; E. Broszeit; C. Berger (pp. 281-285).

The adhesion is a fundamental property of hard coatings in view of tribological-mechanical demands. The quantification of adhesion between coating and substrate is with respect to practice not easy to handle, even so the scratch test is the best established and well discussed test method. The present study analyzes the test procedure and proposes a possible evaluation method and interpretation of the results to reach sufficient reproducibility due to a better standardization.

Corrosion behaviour of coated materials by G. Pajonk; H.-D. Steffens (pp. 285-290).

A well operating corrosion protection essentially prevents corrosive attacks on components and prolongs their endurance. A review of characteristic kinds of corrosion observed on coated components is given and the mechanisms of damage are systematically discussed. Methods of testing are introduced, that allow predictions of sensitivity to the respective types of corrosion.

Density and Young’s modulus of thin TiO2 films by O. Anderson; C. R. Ottermann; R. Kuschnereit; P. Hess; K. Bange (pp. 290-293).

Densities, ρ, of thin TiO₂ layers, produced by reactive evaporation (RE) and ion plating (IP) have been analyzed by means of grazing incidence X-ray reflectometry (GIXR). Depending on the deposition conditions, the layers are amorphous or polycrystalline, with densities between 2.9 g/cm³ and 3.9 g/cm³. Young’s moduli, E, have been analyzed for 280 nm and 500 nm thick layers by means of surface acoustic wave spectroscopy (SAWS) and vary between 65 GPa for RE films and 147 GPa for IP layers. The values are independent of film thickness, but correlate with the density. A phase transition of the TiO₂ films from the amorphous state to anatase occurs at temperatures above 210°C and increases the Young’s modulus significantly, whereas the density remains unchanged.

SIMS-analysis on B, N, and C containing layers by M. Griesser; H. Hutter; M. Grasserbauer; W. Kalss; R. Haubner; B. Lux (pp. 293-296).

B, N, and C containing layers produced by the “Chemical Vapour Deposition” (CVD) method were investigated by SIMS in respect of their elemental composition and impurities. The atomic B/N ratios found are between 1:0.15 and 1:0.46 referred to an h-BN powder (B/N = 1:1 supposed) as reference material. The carbon content was 5 to 12 at-%, additional H and O impurities were detected. Dependencies of the film composition on process parameters and the problems occurring during SIMS measurements of such layers are discussed.

CEMS studies of thermally treated Fe/TiN coatings on Si(1,0,0) by Darko Hanžel (pp. 296-299).

Thin layers of 25 nm ⁵⁷Fe have been evaporated on Si-wafers in high vacuum in order to enhance the sensitivity of Conversion Electron Mössbauer Spectroscopy (CEMS). On the ⁵⁷Fe layer, 25 nm of TiN has been deposited using plasma activated reactive sputtering (Sputron). CEMS enables nondestructive characterisation and determination of physico-chemical properties of iron-containing phases in depth up to 300 nm. Results of Mössbauer spectroscopy have been applied to determine the mechanism for interfacial bonding and the influence of thermal treatment of the samples in UHV up to 873 K. Temperature dependence of the development of different iron-nitrides at the interface Fe/TiN and diffusion of nitrogen into the Fe-layer have been investigated.

On the dynamic range in depth profiling with electron-gas SNMS by W. Bock; M. Kopnarski; H. Oechsner (pp. 300-303).

Despite of the high depth resolution around 1 nm achieved with the direct bombardment mode DBM of electron-gas SNMS, its dynamic range is mostly limited to 3 orders of magnitude. Detailed depth profile studies reveal that crater edge and memory effects contribute with 80% and 20%, respectively, to the limitations of the dynamic range in DBM-SNMS. An experimental remedy has been found by the installation of an additional aperture in the postionization chamber which allows a “geometrical blanking”. By such means the dynamic range is improved by one order of magnitude. Further experiments have shown that the so-called Mesa technique as a specific method for the sample preparation leads to a somewhat smaller improvement.

Characterization of Laser-Arc deposited multilayer systems by means of AES, Factor Analysis and XPS by A. John; Hans-Joachim Scheibe; Holger Ziegele; Steffen Oswald (pp. 304-307).

In a vacuum chamber at 5 · 10^–4 Pa, multilayer systems (single layer thickness 20 nm) consisting of Ti/C and Al/C, respectively, have been deposited on Si (111) disks by the laser assisted coating (Laser-Arc). Structure and composition have been investigated by means of Scanning Electron Microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS), and Auger Electron Spectroscopy (AES) in conjunction with Factor Analysis. AES depth profile measurements through the outermost part of the layers show for both the Ti/C and the Al/C samples a regular structure of the layer sequence metal/ carbon with a constant distance along the sample normal and sharply formed interfaces. In the metallic layers an oxygen enrichment was found, which is more intensive in the Ti/C deposit than in the Al/C one. By means of Factor Analysis in the evaluation of the differentiated spectra as a function of sputtering time, the formation of carbides at the metal/carbon interfaces has been detected. However, in the present state of the investigations it can not be decided, whether the observed carbide formation is the result of the energy impact due to ion sputtering or the coating fabrication process itself.

Preparation of polycrystalline Ti-Al-O films by magnetron sputtering ion plating: constitution, structure and morphology by A. v. Richthofen; Rainer Cremer; Ralph Domnick; Dieter Neuschütz (pp. 308-311).

Ti-Al-O layers were deposited on Si-<100> wafers at 500 °C by means of reactive magnetron sputtering ion plating (R-MSIP). An Al-target was sputtered in rf-mode and a Ti-target in dc-mode simultaneously by an oxygen/argon plasma. The influence of the Al- and Ti-sputter powers on composition, structure, and morphology of the Ti-Al-O layers and the binding states of the components were investigated. The analysis with EPMA, XPS, AES and TEM yielded the following results: Ti-Al-O coatings with different Ti, Al, and O contents in the range of TiO₂ to Al₂O₃ were grown. TEM structure analysis revealed: the pure TiO₂ film consisted of the tetragonal phases rutile and anatase; the two structures were found in the titanium-rich Ti-Al-O film, too, but with significant smaller lattice constants. The aluminium-rich Ti-Al-O film displayed the same cubic structure of γ-Al₂O₃ as determined for the pure Al₂O₃ film, but the lattice constant is significant lower. Evaluation of the TEM pattern of the film with a Ti/Al ratio of 0.8 indicates a hexagonal structure with lattice constants similar to those of κ′-Al₂O₃. All films are nanocrystalline and not textured.

Preparation of cuprite (Cu2O), paramelaconite (Cu32+Cu21+O4) and tenorite (CuO) with magnetron sputtering ion plating: characterization by EPMA, XRD, HEED and SEM by A. v. Richthofen; R. Domnick; Rainer Cremer (pp. 312-315).

Cu-O layers were deposited on Si-<100> wafers at 90° C by means of reactive magnetron sputtering ion plating (R-MSIP). A Cu-target was sputtered in rf-mode by an oxygen/argon plasma, and the influence of the oxygen partial pressure on composition, structure, texture and morphology of the Cu-O layers was investigated. The analysis with EPMA, XRD, HEED and SEM yielded the following results: with an appropriate setting of the oxygen partial pressure, the oxygen content of the films could be controlled between 0 and 50 at-%. XRD bulk structure analysis shows changes in the crystal structure of the films with increasing oxygen content from the fcc structure of Cu, followed by the sc structure of Cu₂O (cuprite), the tetragonal structure of Cu₃ ²⁺Cu₂ ¹⁺O₄ (paramelaconite) to the monoclinic structure of CuO (tenorite). As revealed by HEED, the structure of the near-surface region of the latter two is the same as that of the bulk, whereas in the case of the films with fcc bulk structure, due to oxidation by air, the surface has the sc structure of Cu₂O, and in the case of the film with the sc structure, a monoclinic surface structure of CuO is observed. SEM analyses detected a disordered columnar growth of all Cu-O films.

Density and Young’s modulus of thin TiO2 films by O. Anderson; C. R. Ottermann; R. Kuschnereit; P. Hess; K. Bange (pp. 315-318).

Characterization of interfaces of alumina – high alloyed steels by SST and AES depth profiling by A. H. J. van den Berg; M. A. Smithers; V. A. C. Haanappel (pp. 318-322).

Thin alumina films, deposited at 280° C on several high alloyed steels by low pressure metal-organic chemical vapour deposition (LP-MOCVD), were annealed at 0.17 kPa in a nitrogen atmosphere for 2, 4 and 17 h at 600 and 800° C. The effect of the annealing process on the adhesion of the thin alumina films was studied using a scanning scratch tester (SST) and Auger electron spectroscopy (AES). The best adhesion properties were obtained with commercial oxide dispersion strengthened (ODS) high temperature alloys, especially type PM 3030. From the “normally” high alloyed stainless steels, type AISI-321 showed the best properties. The other stainless steel – alumina combinations showed after a thermal treatment a decrease of the critical load, L_c. Using ODS alloys as the substrate resulted in an increased L_c. AES-studies revealed that the increased L_c can be explained by 1) the presence of sulphur trapping elements, avoiding segregation of sulphur near the interface which could have a detrimental effect on scale adherence, and 2) titanium and carbon enrichment at the interface resulting in a beneficial effect on the adherence between the oxide and the substrate.

Characterization of the stoichiometry of coevaporated FeSix films by AES, EDX, RBS, and electron microscopy by A. Schöpke; B. Selle; I. Sieber; G.-U. Reinsperger; P. Stauß; K. Herz; M. Powalla (pp. 322-325).

The composition of FeSi_x films on Si coevaporated from separate sources of Fe and Si was analyzed comparatively by AES, EDX, RBS, and electron microscopy. Cross-checks between EDX and RBS reveal systematic errors originating from the spectra background subtraction in RBS and from the thickness correction of the EDX signals. PCA (principal component analysis) assisted AES was successfully applied to the characterization of different Si bonding states in nonstoichiometric FeSi_x films. For the growth of β-FeSi₂ films by means of molecular beam epitaxy (MBE) the adjustment of the atomic beam intensities is reported in order to illustrate the capabilities of the various techniques.

Characterization of rhenium-silicon thin films by J. Thomas; Joachim Schumann; Wolfram Pitschke (pp. 325-328).

Rhenium-silicon thin films have been characterized as promising compounds of thermoelectric applications by means of analytical transmission electron microscopy and X-ray diffraction referring to composition, morphology, short-range order and phase formation. Beyond the discussion of the results some methodical aspects and problems are presented.

Investigation of argon ion bombarded RexSi1-x thin film composites by XPS, SEM and AES by R. Reiche; S. Oswald; H. Vinzelberg; C. Metz; J. Schumann; A. Heinrich; K. Wetzig (pp. 329-332).

The electronic structure of argon ion bombarded Re_xSi_1-x films (∼ 100 nm) were investigated by X-ray photoelectron spectroscopy. Argon ion bombardment leads to preferential sputtering of the silicon atoms and produces an subsurface rhenium enrichment. Changes in the core level binding energies and in the valence band structure have been studied as the rhenium concentration in the composites varies between 0 ≤ x ≤ 1 through the metal-semiconductor transition at x ≈ 0.32. The data of the multiplex spectra were subjected to factor analysis in order to determine the relevant components of the ion bombarded metal-silicon system. Four principal components are extracted and are proposed as the pure elements, a rhenium-rich phase and a component near the ReSi₂ stoichiometry. Complementary investigations by SEM and AES provide further proof of the phase assignment in the rhenium-rich component. The silicon-rich component being in composition close to the metal-semiconductor transition can be correlated to the ReSi₂ compound.

Grazing incidence X-ray diffraction analysis of surface modified SiC layers by J. Neuhäuser; G. Treffer; H. Plänitz; W. Wagner; G. Marx (pp. 333-334).

Thin films of silicon carbide with codeposited elemental silicon were prepared by chemical vapor deposition (CVD). In a second CVD-process a thin titanium layer was deposited on the SiC(Si) basic layer. The solid state reaction between titanium and the codeposited silicon can be observed by X-ray diffractometry. A helpful analytical method for the observation of the growth of the reaction products is grazing incidence X-ray diffractometry. Various diffraction patterns of titanium silicides can be obtained by decreasing incidence angles.

Characterization of crystal faces of polycrystalline HFCVD diamond films by STM/STS by R.-J. Schirach; B. O. Kolbesen; D. D. Aderhold; F. J. Comes (pp. 335-338).

Among the numerous techniques available for the characterization of diamond films scanning tunnelling microscopy (STM) in combination with spectroscopy (STS) provides information about the morphology and electronic surface properties down to the atomic scale. Here results of STM/STS obtained on diamond films are reported. 0.5 to 1.25 μm thick films have been grown on silicon substrates by hot filament chemical vapour deposition (HFCVD) by variable CH₄/H₂ mixtures in the range of 0.5% to 3% CH₄. Morphological features of diamond crystallites were studied in detail by STM. A distinct increase of the surface roughness of (111) crystal faces with increasing CH₄ concentration (from 0.5% to 3%) was found. For a CH₄ concentration of 3% (100) faces were smoother than (111) faces. STS revealed significant differences in the tunneling current/voltage (I/V)-characteristics between (111) and (100) crystal surfaces. For (111) surfaces distinct changes in the I/V-characteristics depending on the CH₄ concentration were observed: The I/V-characteristics change and the conductivity increases raising the CH₄ concentration from 0.5% to 3%. This effect is explained with increasing formation of non-diamond carbon (NDC) on (111) surfaces for higher CH₄ concentrations. Thus NDC is also responsible for the enhanced surface roughness observed on (111) surfaces with increasing CH₄ concentrations.

AFM and STM investigations of hydrogenated amorphous silicon: topography and barrier heights by J. Herion; K. Szot; S. Barzen; F. Siebke; M. Teske (pp. 338-340).

As-grown films of hydrogenated amorphous silicon (a-Si : H, highly phosphorous-doped) were investigated by atomic force microscopy (AFM) and scanning tunneling microscopy (STM). Hills up to 10 nm in height and 10 to 20 nm in diameter have been observed by AFM. By using STM in a new high-sensitivity mode, (1) atomically smooth areas (roughness about 0.3 Å rms) which occur at the top of the hills, (2) subnanometer structures several Å in height which cover large parts of the surface have been identified. Simultaneous measurements of the local apparent barrier heights (LABH) show a clear correlation to the topography. Areas showing subnanometer structures have always low LABHs while the highest values of the LABH occur on the smooth areas.

Correction of STM tip convolution effects in particle size and distance determination of metal-C:H films by K. I. Schiffmann; Matthias Fryda; Günther Goerigk; Rolf Lauer; Peter Hinze (pp. 341-344).

Metal containing amorphous hydrocarbon films consist of nanometer size metallic particles in a hydrogen-carbon matrix. Scanning tunneling microscopy (STM) of Au and Pt containing amorphous C:H-films was performed in order to determine particle size- and distance distributions. To correct tip convolution effects, which lead to apparent particle enlargement and particle hiding (1) a method is presented which allows off-line STM tip radius determination by statistical analysis of apparent particle radii and thereby a correct particle radii determination. (2) A simple Monte Carlo model is proposed to compute fractions of hidden particles and their influence on particle distance distributions. Results of these evaluations are compared with results from small angle X-ray scattering (SAXS), transmission electron microscopy (TEM) and X-ray diffraction (XRD).

Atomic resolution of defects in graphite studied by STM by F. Atamny; A. Baiker; R. Schlögl (pp. 344-348).

Different kinds of defects in graphite with a resolution up to atomic scale have been investigated using STM. Mono-atomic steps on the surface as well as bended graphite layers with height differences less than 0.1 nm originating from defects (steps) in the bulk have been uncovered. The influence of such defects on the appearance of superstructures in the surrounding area is demonstrated. Ribbons, with a few nanometers width and less than 1 nm height, and prismatic loops were resolved. Height variations in the range of a few tenths of nanometer as a result of missed and inserted carbon layers have been revealed. To our knowledge, for the first time defect lines on graphite are presented with an atomic resolution. The defect lines are several microns long and only 1–3 atoms in width.

Glass fracture surfaces seen with an atomic force microscope by C. Wünsche; Edda Rädlein; Günther Heinz Frischat (pp. 349-351).

Fracture surfaces of Suprasil 2, Herasil 2, AR glass and Duran glass rods have been studied by an atomic force microscope (AFM) in the contact mode. They could be characterized in the fracture mirror, the mist and the hackle zones. The RMS (root mean square) roughness in the fracture mirror of all glasses investigated increased with growing distance from the origin of the fracture. On several fracture surfaces of different glasses steps have been observed, due to fracture in shear mode. Furthermore changes in the fracture surfaces during scanning have also been observed. They are thought to stem from reactions of the freshly broken glass surface with the surrounding atmosphere and forces between the scanning tip and the soft surface.

Investigation of surface changes on mica induced by atomic force microscopy imaging under liquids by R. Resch; G. Friedbacher; M. Grasserbauer (pp. 352-355).

Surface changes on muscovite mica induced by tip-surface interactions in atomic force microscopy (AFM) experiments under liquids are described. Investigations have been performed with AFM operated both in contact mode (CM-AFM) and in tapping mode (TM-AFM). Additionally, force-distance measurements have been carried out. In contrast to CM-AFM pronounced surface changes can be observed in TM-AFM experiments. However, TM-AFM images of areas previously scanned in contact mode show that imaging in contact mode changes the surface, too. An evaluation of force-distance measurements reveals that these changes depend on the adhesive interaction between tip and sample, which in turn strongly depends on the surrounding medium. The artefact can be avoided by changing the pH-value of the medium or by working with mixtures of ethanol and water. This greatly enhances the applicability of TM-AFM for in-situ investigation of surface processes on mica, which is a frequently used substrate for many technological and biological applications.

AES depth profiles of thin SiC-layers – simulation of ion beam induced mixing by G. Ecke; H. Rößler; V. Cimalla; J. Liday (pp. 355-357).

Thin carbonized SiC layers were investigated by Auger depth profiling. If the layers are smooth, ion induced mixing and Auger electron escape depth are the dominant factors that degrade the depth profiles. With the help of the Monte Carlo simulation code T-DYN by Biersack and an escape depth correction program, simulations can describe the measured Auger depth profiles. For quantitative comparison of simulations and measurements the Auger data must be quantified. The sputter time scale must be converted into depth using a known or best fitting sputter rate. The Auger peak-to-peak height must be converted into concentration using sensivity factors which do not include the sputter correction for selective sputtering. Since these sensitivity factors are normaly estimated at a sputtered single crystal, selective sputter correction must be excluded later. A good quantitative agreement was found for a simulated adsorbate/SiC/Si layer system with a measured Auger depth profile of a carbonized SiC layer on Si. This allows a description of the layer structure and of the composition of the layers.

AES Depth profiling of semiconducting multilayer structures using an ion beam bevelling technique by M. Procop; A. Klein; I. Rechenberg; D. Krüger (pp. 358-360).

An ion beam technique has been developed which allows the preparation of bevels from semiconducting heteroepitaxial structures with smooth surfaces and very flat angles in the order of 0.1°. The bevels are used for AES depth profiling of heterostructures by the line scan technique. Measured and calculated line scans from (Al,Ga)As/GaAs and SiGe/Si test structures are compared to estimate the contributions of the electron escape depth and the ion beam mixing to the depth resolution.

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Analytical and Bioanalytical Chemistry (v.358, #1-2)

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Analytical and Bioanalytical Chemistry (v.358, #1-2)