S. Däbritz

Lattice constant determination from Kossel patterns observed by CCD camera

The Kossel technique is known due to its precision for lattice constant determination in micro ranges by use of X-ray films. Recently we observed the Kossel interferences also by a CCD camera in a good quality. Thus, the diffraction interferences could be immediately processed and evaluated by computer permitting considerable time saving. In order to obtain the similar accuracy as for measurements with X-ray films further technical and experimental improvements were necessary, especially for a better contrast to observe intersection points of several weak reflections, for evaluating digital patterns, for optimizing of the shortest focus-screen distance and for considering the image field curvature of the objective. As a result, a precision in lattice constant determination could be achieved at a Fe-crystal coming relatively close to the one of comparable X-ray film patterns, which is still about one order of magnitude better for the time being.

KOPSKO: a Computer Program for Generation of Kossel and Pseudo Kossel Diffraction Patterns

Diffraction techniques are widely used especially as additional tools for analytical microprobe analysis. A supplementary device to a scanning electron microscope (SEM) allows taking of X-ray lattice source and wide angle interference patterns, now termed Kossel and Pseudo Kossel patterns, respectively, in transmission and back reflection arrangement as reported by DABRITZ et al. (1986, 1997a,b). The developed program KOPSKO simulates exactly the entire reflection system of Kossel and Pseudo Kossel diffraction patterns basing on the geometric diffraction theory. It permits phase, orientation, and structure determination. The present paper shows the wide range of possibilities using the computerized analysis in this field. Initially it deals with simulation of Kossel patterns, which are excellent suitable for a precise determination of lattice constants in the micro range for instance. A new way for simulation of Pseudo Kossel diffraction patterns using three dimensional vector algebra to calculate reflections in point by point procedure is presented in the second part. The attained precise coincidence of simulation and experimentally taken Pseudo Kossel patterns allows a relatively easy determination of crystallographic data of mono- and polycrystals. Particularly the program is designed to determine lattice constants precisely, for the complex divergent beam X-ray interferences, too. Through the three dimensional simulation it takes into account shade originated by the target holder. Moreover, the three dimensional point by point procedure enables the localization of lattice imperfections as well as the consideration of grain size effects in polycrystals. which lead to interruptions of Pseudo Kossel lines. By simulation of diffraction patterns of polycrystalline materials the study of such specimens is essentially simplified.

New observation method for divergent beam X-ray diffraction patterns

The simultaneous observation of X-ray reflections by a high-quality charge coupled device (CCD) camera in a scanning electron microscope is presented. The possibility of immediate further processing and evaluation of the images by computer, avoiding the extensive photographic X-ray film procedure, is discussed. The divergent beam X-ray method has considerable importance for investigations in materials research. The experimental set-up is described and the advantageous application of the camera is demonstrated for different examples.

Neuere Ergebnisse auf dem Gebiet der Kossel-Technik

ZusammenfassungFür binäre Systeme mit Anteilen der Komponenten zwischen 10 und 90% läßt sich mit der Kossel-Technik über Präzisionsgitter-konstantenmessungen eine sehr genaue Konzentrationsbestimmung durchführen. Das trifft sowohl für intermetallische Verbindungen als auch für Mischkristalle zu; in einigen Fällen gilt das sogar dann, wenn die Atomradien der Komponenten sich nur wenig unterscheiden. Über eine engere Kopplung der Kossel-Technik mit der Elektronenstrahl-Mikroanalyse läßt sich die Genauigkeit der Konzentrationsbestimmung steigern und die elektronenstrahl-mikroanalyti-schen Korrekturverfahren können auf diesem Wege überprüft und verbessert werden.Die Kossel-Technik ist geeignet, die Vorgänge bei kristallogra-phischen Phasenumwandlungen sowohl im Tieftemperaturbereich als auch im Hochtemperaturbereich zu studieren. Sich dabei ändernde Realstrukturparameter, wie z. B. die Versetzungsdichte, lassen sich erfassen.Die Intensität von Kossei-Linien, die an A- und B-Seiten von AIIIBV-bzw. AIIBVI-Halbleitern entstehen, ist deutlich verschieden, so daß sich die Kossel-Technik als ein neues Untersuchungsverfahren für Halbleiteroberflächen anbietet.Die Experimente zur Herstellung von Kossel-Aufnahmen mit Protonenstrahlanregung belegen, daß die Kopplung von Kossei- und Protonenstreuexperimenten an Einkristallen neue kristallphysikalische Aussagen zu liefern vermag.SummaryFor binary systems with anteils of the components between 10 and 90%, a very precise concentration determination can be performed via precision measurements of lattice constants. This applies both to intermetallic constants and also to mixed crystals, in some cases even when the atomic radii of the components differ only slightly. The accuracy of the concentration determination can be increased by a closer coupling of the Kossel technique with electron ray microanalysis. In this way, the electron ray methods of microanalytic correction may be checked and improved.The Kossel method is suitable for studying processes in crystallo-graphic phase transformations both in the low temperature and in the high temperature range. Alterations in real structure parameters can be detected, e.g. the density of staggered arrangement.The intensity of Kossel lines, which arise on the A and B sides of AIII BV and AII BVI semiconductors, is distinctly different, so that coupling of Kossel and proton scattering experiments on single crystals may supply new data on crystal physics.

Investigation of the three-dimensional microstructure of Cu-Sn(Pb) diffusion zones by means of ion beam sputtering, scanning electron microscopy and lattice source interferences

On model substances of Cu-Sn(Pb) solders it is shown by the combined use of several physical analytical methods that the intermetallic compounds formed during the annealing process have a crystalline structure, which can be observed also three-dimensionally by ion etching. Moreover, grain boundaries as well as phases become visible, and it is possible to determine the crystallographic orientation of the individual crystals in the Cu starting material and in the diffusion zones by means of the Kossel technique. As a result of the investigations, conclusions can be drawn with respect to the diffusion process, especially also to the crystallographic structure of the diffusion zones and the dendritic growth.

Detection of crystal lattice defects in microranges of copper by X-ray interferences

The lattice source interferences (LSI) or Kossel technique and the divergent beam X-ray interferences (DBI) or pseudo-Kossel technique are highly sensitive to the real structure in the microrange of the crystal lattice. Both methods complement each other, owing to their geometrically different diffraction regions. Mechanically ground and polished Cu single crystals with different crystallographic orientations ([100], [110], [621], [694]) and two polycrystalline Cu specimens were chemically etched stepwise with FeCl 3 ·6H 2 O. After each etching time, divergent beam X-ray patterns of the crystals were taken and in some cases lattice source interferences pattern also. It was possible to observe the real structure as a function of the depth, because the information comes from a depth of about 2-5 µm for LSI and 50-100 µm for DBI. The DBI patterns show, for instance, for Cu [100], sharp interference lines from regions up to 40 µm deep. With increasing depth the crystal lattice reveals the real structure only and not the deformation effect caused by polishing.

Short circuit diffusion in CuSn6/Ni/Au planar tricouples

To investigate processes of short circuit and uphill diffusion, low-temperature diffusion experiments were carried out with sandwich samples of CuSn6/Ni/Au in the kinetic regimeB after Harrison. Two kinds of base material CuSn6 with different grain sizes were chosen. The first material was cold rolled CuSn6 with a mean grain size of 3–4 μm. The second was annealed CuSn6 with a mean grain size of 40 μm. The Ni and Au layers with thicknesses in the μm range were deposited by galvanization. The sheets were prepared by ion beam slope cutting, characterized by scanning electron microscopy and transmission electron microscopy. After annealing at 576 K up to 120 d, the samples were investigated with glow discharge spectroscopy and scanning electron microscopy. Concentration penetration plots made with glow discharge spectroscopy showed a different diffusion behaviour dependent on the CuSn6 material. The diffusion processes in the samples of cold rolled CuSn6 are more extensive than in the annealed CuSn6 samples. To find out causes of this phenomenon, a model of short circuit diffusion was developed and concentration penetration curves were calculated numerically with the finite difference method. Images of an ion beam slope cut sample show grain growth in the Au layer.

Combined use of ion beam slope cutting and scanning electron microscopy for the investigation of the 3-dimensional micro-structure of alterated mediaeval glass

Ion beam slope cutting (IBSC) has been developed as a preparation method for SEM and TEM to avoid the problems which occur using the common mechanical preparation techniques. IBSC has been practised on metals, plastic composites ceramics and alterated mediaeval glass, too. For the investigation of the 3-dimensional microstructure of the glass samples, IBSC has been the only method, which will enable a small cut without destroying the valuable cultural heritage. By SEM investigations of the ion beam cut, the alteration process of mediaeval glass has been observed starting on the surface and spreading into deeper zones of glass. Vertical and lateral cracks are only developing and spreading in the surroundings of crater erosions. The cracks cause splitting of parts near the surface of glass. Inside the cracks, harmful atmospheric gases, like SO2 and CO2, are reacting with the main glass components to alterations salts, which will build up a white and black crust on the surface and in zones near the surface.