Versetzungsinduzierte Brechzahlinhomogenitäten

Inhomogenities of refractive index decisively influence the optical quality of elements for high precision optics. The present paper investigates the variation of refractive index induced by crystal defects, especially by dislocations. On the basis of the results for cubic crystals published by Nikitenko and Dedukh, equations were derived to calculate inhomogeneities induced by a dislocation in a generally anisotropic crystal. Numerical evaluations of the theory are performed for real dislocations in ADP, KDP and α-quartz.     

Der Kanteneffekt als Fokussierungshilfe in Elektronensondengeräten

In the Scanning Electron Microscope with backscattered electrons a characteristic contrast is found at edges, the vertical flanks of which are directed to the detector. Everharts backscattering theory is applied to examine the magnitude of the effect and to discuss the influences of the object material, detector position, and spot diameter. By means of the effect the beam focusing is reduced to an intensity measuring.     

Gitterkonstantenänderungen und chemische Inhomogenitäten von tetragonalem ZnSiP2

X-ray lattice parameter measurements in small specimen volumes of ZnSiP₂ crystals by means of the Bond method demonstrate local chemical inhomogenities probably caused by changes in Si concentration up to about 0.8 atomic p.c.     

Näherungsverfahren für die Integraldarstellung von Beugungsintensitäten gestörter Kristalle

For the calculation of the electron microscopic diffraction contrast without column approximation a solution is given by a perturbation calculation. Applying this to the two-beam case one gets integral representations for the amplitudes of the diffracted waves.     

Zur Errechnung der Intensitäten von Auger-Übergängen für die quantitative Analyse von Festkörperoberflächen mit der Augerelektronenspektroskopie (AES)

According to an empirical equation for the Auger electron intensity arising from primary electron bombardment of solid surfaces, the parameters such as ionization cross section, relative Auger transition probability, backscattering factor and mean escape depth were evaluated for the L₃M₄₅M₄₅ Auger transition of elements with atomic number Z = 22 to 33. A comparison of the calculated relative intensities with experimental values from Palmberg et al. indicates a good agreement of both curves representing the intensity in dependence of atomic number. The mean relative deviation of calculated intensities from measured ones amounts to 20%. This is nearly the same value, as it has been estimated so far for the accuracy of quantitative AES without standard. Examining the influence of individual intensity parameters we were able to show that above all the ionization cross section and in the present case also the relative Auger transition probability determine the value of intensity.     

Untersuchungen zum Einfluß von Temperatur und Versetzungen auf die integralen Röntgenintensitäten von Si-Einkristallen

It is possible to determine the Debye-temperature from measurements of the absolute integral X-ray intensities of silicon single crystals. Debye-temperatures of 543 to 533 K were found for a dislocation-free silicon crystal for temperatures between 90 and 296 K. The effect of dislocations on the Debye-temperature in silicon was investigated for various temperatures.     

Polaritätsabhängige Struktureffekte in tetraedrisch koordinierten Halbleitern

On the basis of the semiempirical dielectric theory of structure a sensitive parameter accounting for the relative stability of the zincblende and the wurtzite structure in epitaxial layers of A_IIB_VI-compounds on (111)-orientated A_IIIB_V, Si, and Ge substrates is introduced. The statements of the proposed theoretical model are in good agreement with the experimental results.     

Funktionelle Abhängigkeiten der Gleichgewichtsverteilungskoeffizienten in Molybdän

From the deeper investigation of the periodicity of the equilibrium distribution coefficient in molybdenum comes out that k_c values of admixtures (transition metals) in Mo depend on three factors of influence: a) the valence factor (the number of valence electrons), b) the dimension factor (the real or hypotetical melting point of the admixture phase, which is the same as that one of the basic metal Mo—KSC.) From this dependence it is possible to predict the value k_o of the elements in molybdenum, the diagrams of which are not known or inexact.     

Orientierte Einlagerungen von Nonylphenolpolyglykoläthern in Zwischenschichträumen von Montmorillonitkristallen

Polyoxathylated nonylphenols were adsorbed by hydrogen bonding to oxygen-rich montmorillonite surfaces. These compounds were also held in the interlayer spaces of montmorillonite and tended to form mono- and double-layers. The kind of complexes and the orientation of molecules in the interlayer spaces are discussed.     

Untersuchung epitaktischer Molybdänkarbidschichten an Molybdän-(110)-Oberflächen

The initial phases of high temperature (1700 K) carburization of (110) molybdenum surfaces by C₆H₆ at low pressure are examined with low energy electron diffraction (LEED) and emission electron microscopy. After an exposition of about 8 · 10⁻⁵ Torr · sec a (4 × 4) superstructure was observed by means of LEED, interpreted as coincidence lattices with the Mo₂C (10.0) plane parallel to the Mo (110) surface. Heating a sample without further exposition resulted in the appearance of a complex and of a (2 × 2) superstructures. After an exposition of about 2 … 9 · 10⁻³ Torr · sec needle shaped molybdenum carbide crystallites grew on the surface into the [111] and [111] directions. The orientation Mo₂C (10.1) parallel to Mo (110) was concluded from the LEED patterns.     

Präparation und Charakterisierung von Granateinkristalloberflächen

The preparation of single crystal substrates of gadolinium gallium garnet as a typical example of a brittle material is described. The mechanical polishing with iron oxide and diamond as well as a mechano-chemical polishing procedure basing on SiO₂/H₃PO₄ are investigated. Working damage is investigated by X-ray topography, double crystal spectrometry and selective etching. Results are discussed in the frame of a brittle fracture model of the abrasion process.     

Anisotrope Längenänderungen bei spannungs- und verformungsinduzierter martensitischer Gitterumwandlung kubisch-flächenzentriert → hexagonal

With the elastic and plastic deformation of the steel X8Mn16, respectively, a stress or deformation induced transformation of the fcc γ-matrix lattice into the hex. ϵ-martensite occurs, being connected with anisotropic changes in length, and leading to a decrease of the apparent elastic modulus of the alloy. A further investigation shows it is obviously the question of the result of the strain-memory effect, until now not yet being observed with iron alloys. Similar anisotropic changes in length can be taken into account with all pure metals and alloys, the martensitic transformation of which turns out under the influence of an outer uniaxial stress.     

Umwandlungsplastizität und Form-Gedächtnis-Effekt in einer Eisenlegierung mit 16% Mangan

During the quenching of wire shaped specimens of steel X8Mn16 fec austenite changes under reduction of length in hcp ϵ-martensite. If the transformation takes place under the influence of an external tensile stress an elongation results. This transformation plasticity consists of a reversible and an irreversible part. The reversibel part rises by the formation of stress-induced ϵ-martensite in preferred orientation and is built back under reduction of length during the following heating over the Af-temperature. By this it is verified that the strain-memory-effect can occur in iron alloys too. A plastic deformation of the austenite below the recristallisation temperature prevents the γ → ϵ-transformation.     

Strukturuntersuchungen an Oberflächenschichten spanend bearbeiteter Molybdän-Einkristalle

Molybdenum single crystals were used as model samples for gross machining operations (turning). The damaged surface layer was studied by reflection electron diffraction and transmission electron microscopy (TEM). Near the machined surface the material was found to be polycrystalline, the transition to the single crystal state occurs within the range from 2 to 5 μm. Pronounced plastic deformations are ranging to a depth of about 150 μm below the surface. The transition to the undisturbed single crystal occurs within the range from 150 to 300 μm.     

Versetzungsätzungen und Mikrohärtemessungen an druckverformten Reinsteiseneinkristallen

The dislocation occurring at single or repeated loading in metals is mainly explained by the dislocation process. The results of investigation available are a contribution to the detection of the connection between dislocation density and work-hardening.     

Zur elastischen Wechselwirkung von Punktdefekten und Einschlüssen in der Nähe von Festkörperoberflächen

Calculating the interaction energy of point defects and inclusions in solids the influence of solid surfaces usually is neglected. But in the immediate vicinity of the boundary surfaces the deformations around the defects are, connected with a certain extra contribution to the total energy which was calculated applying continuum mechanics methods. The medium is assumed to be isotropic and homogeneous. An analytic expression for the interaction energy of two spherical inclusions near a half-room boundary surface is derived. The results show the interesting phenomenon that both attraction and repulsion between the defects occur, only depending upon the geometrical parameters.     

Einfluß der Substruktur auf die optische Homogenität von Rubin-Laserstäben

The relation between mosaic structure and optical homogenity was measured of 90° ruby laser rod. The optical homogenity was measured by the interferometric method and the mosaic misorientation by Berg-Barrett method and the oscillation spectrometer respectively. The proportionality between the number of the interference stripes and the rotation of the mosaic blocks about an axis perpendicular to the growth axis and crystallographic c-axis was found.     

Ferroelastic domain walls in BiVO<Subscript>4</Subscript>

Analysis of the domain structure is performed using the method of matching strains at the interface and the model of thin domain walls. Equations describing the matching interlayers for crystal lattices are derived and the interlayer parameters are obtained for all possible types of domain walls in BiVO₄. It is shown that the matching interlayers have monoclinic symmetry. A difference between the elastic energy of a domain wall and the parameters of adjacent orientation states is revealed.