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In this work we studied the impact of the growth mode on structural and optical properties of thick GaAsN layers grown on GaAs (100) substrates using plasma-source molecular beam epitaxy. The investigated GaAsN layers had similar average nitrogen content (N ~ 1.4–1.6%), but were formed using different growth approaches. We found that both structural and optical properties of GaAsN layers crucially depend on the growth mode. We observed the formation of an ultrashort-period monolayer GaAsN–GaAs superlattice upon pulsed GaAsN deposition with laterally modulated nitrogen composition. We attribute this phenomenon to self-organization of nitrogen-rich and nitrogen-poor domains due to phase separation. We demonstrate the possibility of forming short-period GaAsN/GaAs superlattices using multi-cycle GaAsN deposition in order to fabricate high planarity lateral domain structures suitable for fundamental research and practical applications.

Optical properties of MBE-grown ultrathin GaAsN insertions in a GaAs matrix have been studied, with the goal of deriving methods for the intentional formation of carrier localization regions in GaAsN layers. In the case of a short-period GaAs/GaAsN superlattice, an additional long-wavelength line is observed in the photoluminescence spectrum. Comparison of the optical data with the transmission electron microscopy data shows that this line is related to the emission from the formed regions enriched with nitrogen (up to 8.5%). The characteristic size of these nitrogen-enriched regions in upper layers of the superlattice is larger than in lower ones, and it increases with the number of the deposited layers increasing.

For various material systems of low dimensions, including multilayers, islands, and quantum dots, the potential applicability of transmission electron microscopy (TEM) is demonstrated. Conventional TEM is applied to elucidate size, shape, and arrangement of nanostructures, whereas high-resolution imaging is used for visualizing their atomic structure. In addition, microchemical peculiarities of the nanoscopic objects are investigated by analytical TEM techniques (energy-filtered TEM, energy-dispersive X-ray spectroscopy).

Quantitative high-resolution transmission electron microscopy (qHRTEM) is methodologically extended towards the assessment of occupationally and positionally modulated structures. For this purpose, iterative digital image matching has been combined with data processing within the Rietveld refinement code JANA2000. In this approach, the number of free parameters is kept low and rather complicated modulated structures become assessable by qHRTEM. The feasibility of the improved methodology is demonstrated for the 1D modulated structure of Ba(2)TiGe(2)O(8).

The local chemical concentrations of the elements in the nickel-base single crystal superalloy SC16 were examined by electron microscopy and atom probe tomography after standard heat treatment and creep deformation of 0.5% at 1223 K along the [0 0 1] direction. Creep deformation led to directional coarsening of the γ′ precipitates. The atom probe measurements were carried out along the [0 0 1] and [0 1 0] directions. Enrichment of Al and slight depletion of Ti in the γ′ precipitate near the γ′/γ interface were observed after creep deformation, whereas in the γ phase both these elements were depleted. An enrichment of Cr was detected near the interface in γ channels perpendicular to the applied stress. Small γ′ precipitates (size ∼3 nm) were observed by atom probe in the γ-matrix indicating non-equilibrium state of the alloy.

The incommensurately modulated structure of the fresnoite framework-structure type compound Ba2TiGe2O8 has been solved using a (3 + 1)-dimensional superspace approach. The structure is orthorhombic and adopts the superspace group Cmm2(0,β,1/2)s00 with β ≃ 0.635 at room temperature. The refinement was based on neutron powder diffraction data obtained from a powdered single crystal grown by Czochralski pulling. The modulation parameters that were obtained support the idea that frozen-in rigid-unit modes cause the modulation. The modulation is mainly manifested by positional displacements of O atoms. Barium ions are either eightfold, ninefold or tenfold coordinated in the one-dimensional modulated structure. A significant improvement of the bond-valence sum for both barium positions is achieved by the introduction of the positional modulation. This finding strongly suggests that underbonded barium positions are critically involved in provoking the incommensurate modulation in Ba2TiGe2O8.

Metalorganic vapor phase epitaxy of GaSb quantum dots (QDs) grown on top of a layer of InAs seed QDs shows a vertically aligned correlation if thin GaAs spacer layers deposited at low temperature are used. Introduction of an annealing step after spacer deposition strongly improves the crystalline quality of the spacer layer. Vertically anticorrelated ordering is found on annealed spacers in addition to aligned ordering. Good optical properties are achieved for stacked QD structures with an InGaAs QD layer on top of seeded GaSb QDs. The photoluminescence of these structures is red shifted by 75 meV with respect to the emission of a single InGaAs QD layer.

Sr 2 TiSi 2 O 8 single crystals were grown by Czochralski pulling and from a high-temperature solution. X-ray diffractometry revealed the modulated crystal structure of Sr 2 TiSi 2 O 8 to belong to the 5D superspace group P 4 bm (− α , α , 1/2; α , α , 1/2) with α =0.3. Atomic positions, anisotropic displacement factors and positional modulation parameters for Sr 2 TiSi 2 O 8 are determined and discussed. The positional modulation is further investigated by electron diffraction and high-resolution transmission electron microscopy. In the latter experiments, the 2D modulation appears to be superimposed by some 1D modulation waves. This effect is discussed in terms of growth conditions.

The formation of GaSb quantum dots on a GaAs (0 0 1) substrate under metalorganic chemical vapor deposition conditions is investigated. Transmission electron microscopy images and photoluminescence measurements show the island density to be determined in an initial kinetically controlled phase. Subsequently, mass transfer from the two-dimensional wetting layer sustains the growth of the GaSb quantum dots (QDs). Many-particle e=ects in the type II QDs are investigated by excitation- and temperature-dependent photoluminescence measurements. The peculiar optical behavior is dominated by Coulomb charging and state ?lling of the localized holes. ? 2002 Elsevier Science B.V. All rights reserved.

This study examines how far traces of the Nazi past can still be found in the psychological family environment of college students and academics attending a counselling centre two generations after the end of World War II. It considers how such traces can be elicited in discussions and tackled systematically within a therapeutic context. It was found that many families had never talked about their memories of the Nazi period, ignoring or repressing them. This study showed that the failure to discuss such topics within families was of decisive significance during counselling sessions, and that current problems often relate to an unprocessed family past.

In this paper we have investigated the effect of CF4 plasma treatment on AlGaN/GaN HEMTs and compared it with Ar plasma treated devices. We have investigated the electrical characteristics of the devices using transistor characteristics as wells as CV measurements in order to verify the impacts of the different treatments on the electron concentration in the 2DEG. Furthermore, a TEM-EDX analysis was performed to find out if any fluorine incorporation in the AlGaN barrier during the CF4 plasma treatment occurs. No significant impact of the fluorine on the threshold voltage could be determined, We conclude that fluorine incorporation is not responsible for the threshold voltage shift. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Ap }i}n doped pc-silicon thin "lm grown by means of hot wire chemical vapour deposition (HW CVD) on a zinc oxide "lm has been investigated by transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS). The structure of both layers, the ZnO substrate layer as much as the silicon thin "lm and the chemical composition at the interface were the subjects of our investigations. We found that a "le of pure silicon with a thickness of about 5 nm covers the substrate surface. A plausible model for getting information on the wavyness of the interface ZnO/pc-Si and the thickness of this pure Si-layer was developed. 2001 Elsevier Science B.V. All rights reserved.

The structure of the off-stoichiometric In-rich ternary phase CuIn 5 Se 8 was studied by means of electron diffraction and high-resolution electron microscopy. The compound shows a layered structure with a 7-layer stacking sequence of closed-packed planes, which contains both cubic and hexagonal stacking of Se atoms. The studied CuIn 5 Se x bulk crystal is known as the β-phase of this compound.

By marking the solid-liquid interfaces during a stepwise decrease of the height of a stationary molten zone of Bi 0.5 Sb 15 Te 3 reasonable and changing curvatures of the interfaces are determined. In opposite to the lower interface the upper interface changes its shape from convex to concave for aspect ratios ar ≥ 2. The differences regarding the shape of both interfaces are indirectly due to the different flow intensities in both half zones. Furthermore, in addition to experiments described in Part 1 of this paper the molten zone was moved dynamically through the sample (zone melting). By estimating solutal and thermal RAYLEIGH numbers the solutal contribution to buoyancy convection is considered as negligible compared to the thermal part for the investigated zone heights. Time-dependent convection during zone melting results in pronounced striations. With suitable models for the correlation between the oscillations of temperature, growth rate and microscopical concentration it was possible to estimate the shape and quantity of oscillating compositional inhomogeneities (striations).

Many-body states in self-organized type II GaSbAs/GaAs quantum dots grown by metal organic chemical vapor phase deposition are studied. With increasing exciton occupation the photoluminescence shows a blue shift and becomes significantly broader developing a saturated plateau structure. The results reveal the properties of many-hole states in GaSbAs quantum dots determined by Coulomb charging and state filling.

A (110) twin domain in Ba2TiGe2O8 was imaged using high-resolution transmission electron microscopy, HRTEM. The interface would not be visible due to the very weak orthorhombic deformation of the unit cell (0.15 %) alone. But since a modulated structure along the b*-direction is developed, the boundary can be localised. An experimental method for the detailed characterisation of the atomistic domain-boundary structure is proposed.

Strain-driven decomposition of an alloy layer is investigated as a means to control the structural and electronic properties of self-organized quantum dots. Coherent InAs/GaAs islands overgrown with an InGa(Al)As alloy layer serve as a model system. Cross-section and plan-view transmission electron microscopy as well as photoluminescence (PL) studies consistently indicate an increase in height and width of the island with increasing indium content and/or thickness of the alloy layer. The increasing island size is attributed to the phase separation of the alloy layer driven by the surface strain introduced by the initial InAs islands. The decomposition is enhanced by the addition of aluminum to the alloy layer. The ground-state transition energy in such quantum dots is significantly (up to 200 meV) redshifted compared to the original InAs/GaAs quantum dots, allowing to reach the 1.3 \ensuremath{\mu}m spectral region maintaining the high PL efficiency and the low defect density typical for Stranski-Krastanow growth. The possibility of degradation less stacking of such quantum dot layers enables injection lasing on the ground-state transition with a differential efficiency of 57% and a continuous-wave output power of 2.7 W.

Self-organized formation of GaSb quantum dots during MOCVD growth has been studied. Thin GaSb layers are deposited on GaAs (0 0 1), followed by a growth interruption before the deposition of a GaAs layer. The GaSb growth is performed using low V/III ratios and growth temperatures between 510°C and 550°C. Undercritical GaSb depositions lead to inhomogenities in the composition and thickness of such layers. Photoluminescence measurements suggest these quantum islands to provide zero-dimensional confinement for holes. The dependence of the luminescence on the growth temperatures indicates the formation of the quantum islands to be kinetically controlled.

The influence of the GaAs cap layer thickness on the surface morphology and stoichiometry of InAs quantum dot (QD) layers grown on GaAs(0 0 1) was investigated by real-time reflectance anisotropy spectroscopy (RAS) and ellipsometry. A redistribution of InAs from partially covered islands to the surface of the GaAs cap layer was found. Introducing a well-defined growth interruption (GRI) during cap layer growth, a narrower size distribution of the InAs islands could be achieved and, moreover, large clusters and dislocations in the sample could be completely avoided. Transmission electron microscopical images of stacked QD layers substantiate the growth model of island redistribution by showing a fractional second wetting layer. Using this procedure of island redistribution dislocation free 5-fold InAs QD stacks were realized.

The microstructure of (Ga,In)P layers grown by metal organic vapour phase epitaxy (MOVPE) at 580°C was characterized by transmission electron microscopy (TEM), especially by electron diffraction (TED). In lattice-matched (Ga,In)P layers grown on exactly oriented (001) GaAs substrates or low misoriented ones additional intensity maxima occur at about 1/2 1/2 0 interpreted as ordering parallel to {110}. The {110} ordering is present in both undoped and doped layers. The well-known (1-11) ordering was detected in layers grown on (001) substrates with larger misorientation (2° off to {111}B). For the various ordering types a model was developed on the basis of stacking of ordered (001) planes as a kind of polytypism.

The off-stoichiometric In-rich phase CuIn 3 Se 5 was studied by means of electron diffraction and high resolution electron microscopy. The structural investigations provide unambigouesly a tetragonal structure of this compound which can be derived from the chalcopyrite structure of CuInSe 2 . A theoretical model with an ordered occupation of vacancies is discussed for this structure. A detailed comparison between the theoretical model and the experimental archieved one's is revealed.

Planar ordering of dense self-organized arrays of InP/In 0.48 Ga 0.52 P quantum dots is investigated using grazing incidence small-angle X-ray scattering (GISAXS), atomic force microscopy (AFM), and transmission electron microscopy (TEM). Using the two-dimensional Fourier transform of the AFM data together with the GISAXS data, we show that the degree of ordering increases with increasing InP deposition time and, therefore, with increasing quantum dot density. This increase in ordering is seen both in that the dot period is less variable and in the appearance of longer ranged ordering of the dots on the surface. Intense photoluminescence due to radiative recombination of heavy holes and electrons in the quantum dots is observed at an energy between the band gaps of InP and In 0.48 Ga 0.52 P. ( 2000 Elsevier Science B.V. All rights reserved.

Molecular dynamics simulations using empirical potentials are applied to characterize the structure, the energy relaxation and the stability of pyramidal-shaped quantum dots in the CdSe/ZnSe system. The relaxed structure models are used for a reliable interpretation of electron microscope investigations to analyze the size, the shape and the strain fields of the quantum dots. Though the elastic strains modify the electron microsope image contrast by creating virtual truncations of the pyramids or additional black-white lobes, optimum imaging conditions chosen will reveal the shape and the size of the dots.

We present a new method for the determination of the magnetic moment distribution (µ) of ferrofluid particles from the magnetization curve measured on diluted ferrofluid samples in the liquid state. The method employs the solution of the standard integral equation describing the magnetization of a non-interacting particle system in the given external field as a convolution of the Langevin function with the distribution of particle moments. No a priori assumptions concerning the shape of the corresponding distribution are required. We present the reconstruction results obtained both for the computer simulated magnetization curves and for real experimental data. In the latter case we compare the distributions found using our algorithm with those calculated from the particle size distributions obtained via the electron microscopy images of the ferrofluid particles.

The microstructure of epitaxial CuInS 2 , CuGaSe 2 and polycrystalline CuInS 2 films was studied by transmission electron microscopy. We found that the vapour-phase epitaxy of CuInS 2 below the transition temperature T c results in films with chalcopyrite and CuAu-like structures. The formation of CuAu-like ordered phases within the films is independent of the substrate orientation, whereas the amount of CuAu-like ordered Cu and In atoms can be influenced by the substrate orientation. The co-existence of chalcopyrite and CuAu-like ordering of the metal atoms was also found in polycrystalline CuInS 2 films prepared by sulphurization of Cu/In metal precursor at a temperature below T c . In contrast, vapour-phase epitaxy of CuGaSe 2 below T c provides only films with the chalcopyrite structure. The experimental finding is in good agreement with the results of first-principle band-structure calculations.

Self-organized CdSe/ZnSe quantum dots (QDs) were investigated by means of transmission electron microscopy (TEM). Plan-view diffraction contrast images each obtained under individual diffraction conditions showed different contrast behaviour. Bright-field imaging of single dots revealed circle-like contrast features. In the 040 dark-field image a 2-fold symmetry and in the 220 dark-field image a nearly 4-fold symmetry of the contrast features were observed. Supplementary strain-field calculations using a finite-element method were compared with the experimental contrast features. The distributions of the several strain components chosen according to the certain diffraction conditions show the same symmetry and orientation as the experimental features.

InAs quantum dots grown in a GaAs matrix are investigated using capacitance transient spectroscopy and transmission electron microscopy (TEM). Trap states are measured which are associated with the presence of the quantum dots but are too deep to be interpreted as the intrinsic electronic levels of the quantum dots. TEM allows us to rule out traps caused by threading dislocations in the GaAs matrix. The trap occupation measured from capture data is a highly non-exponential function of the filling pulse duration and, together with double DLTS measurements, indicate that the traps are electrically coupled in two dimensions and located in the plane of the dots. We propose that the measured deep levels are due to point defects in or near the quantum dots.

Cr 3+ -doped LiCaAlF 6 single crystals, considered as promising laser materials, contain secondary phases of different sizes and shapes which can be observed as needles or dust by light microscopy. TEM investigations presented in this paper give evidence for precipitation as the reason for the so-called microscopic dust. The elongated shape of the so-called needles seems to be a consequence of the microscopic growth of facets which become visible by the decoration of the facet boundaries with microscopic precipitates.

Analytical transmission electron microscopy was applied to characterize the size, shape, real structure, and, in particular, the composition of different semiconductor quantum structures. Its potential applicability is demonstrated for heterostructures of III-V semiconducting materials and II-VI ones, viz. (In,Ga)As quantum wires on InP and (In,Ga)As quantum dots on GaAs both grown by metal organic chemical vapor deposition, and CdSe quantum dots on ZnSe grown by molecular beam epitaxy. The investigations carried out show that the element distribution even of some atomic layers can be detected by energy-dispersive X-ray spectroscopy, however, exhibiting a smeared profile. Contrary to that, sub-nanometre resolution has been achieved by using energy-filtered transmission electron microscopy to image quantum dot structures.

Incommensurate modulations in Ba 2 TiSi 2 O 8 , Sr 2 TiSi 2 O 8 , and Ba 2 TiGe 2 O 8 are compared based on their corresponding electron diffraction patterns. The dependence of the modulations on chemical composition provides a suitable model system for the investigation of incommensurations in framework structures using high-resolution transmission electron microscopy (HRTEM). A widening of quantitative HRTEM utilising the concept of rigid units is proposed allowing for a determination of atomistic displacements responsible for the formation of incommensurately modulated structures.

Compositional inhomogeneities of (Si,Ge) single crystals grown by the radio frequency (RF) heated float zone technique have been studied using the back-scattered electron (BSE) mode of a scanning electron microscope. Numerical analysis of the images by Fast Fourier Transformation (FFT) showed that the number of spatial frequencies with substantial amplitudes is increased when investigating longitudinal sections of crystals containing dislocations instead of dislocation-free crystals. This can be attributed to different growth conditions in terms of super-cooling.

Bi–Sb single crystals with a well defined slope of composition have been grown by the gradient projection method (GPM). The gradient crystals obtained exhibit a lattice parameter gradient of Δ a / ā /d z =0.835%/cm and Δ c / c /d z =0.79%/cm. The concentration profiles of the grown crystals show a good approximation to a linear distribution. By adjusting the growth rate and using a single crystalline seed the quality of the grown crystals could be drastically increased.

Bulk single crystals of ZnSe have been grown by the travelling heater method (THM) with SnSe as a new and novel solvent. This solvent is favoured for the growth of ZnSe because of the nearly ideal phase diagram for SnSe–ZnSe. ZnSe has a suitable solubility in liquid SnSe in the temperature range of 950–1050°C and there is practically no solubility of SnSe in solid ZnSe. Ingots were grown with dimensions of 10 mm in diameter and about 30 mm in length. The crystals are characterized by greatly reduced density of inclusions, mostly of small sizes. Moreover, their high degree of structural perfection was confirmed by X-ray double-crystal topography and rocking-curve measurements.

As a function of material-specific properties a multiple substrate treatment (MST) for preparation of (0 0 1) ZnSe surfaces for homoepitaxy was developed including cutting, mechanical processing, chemo-mechanical polishing procedure and a final step of chemical polishing. The resulting average roughness of the treated surfaces investigated by atomic force microscopy is less than 1 nm when MST is completed. High-resolution X-ray diffraction topography has been carried out to detect the underlying structural degradation caused by mechanical and chemo-mechanical polishing. The thickness of the damaged layer determined by high-resolution X-ray diffraction rocking curve measurements using 311 reflection (penetration depth ≈800 nm) is about 10 μm and can be removed by means of a final chemical polishing step.

Selectively-doped heterostructures based on both GaAs and InP containing several atomic layers coverage of InAs as both strained 2D and partially relaxed 3D (quantum dot) have been grown by gas source molecular beam epitaxy and the transport properties have been investigated. We show that while coherently strained InAs in 2D layers results in increased electron mobilities, the formation of 3D quantum dots appear to trap electrons and decrease significantly the mobility of those remaining. The degree of trapping is dependent on the size and density of the dots.

We present structural and optical properties of InAsP and InGaAs quantum wire structures in situ grown by MOCVD utilizing arsenic/phosphorus exchange as the preparation method in InP V-grooves. Transmission electron microscopy images show defect free structures. Optical spectroscopy methods reveal a ground state luminescence at 1.163 eV for InAs x P 1− x wires. The emission energy can be varied by several 10's of meV by growing InGaAs after the exchange process. We report also on In x Ga 1−x As quantum wires with ground state emsission at 0.970 eV. The homogeneity of these wires is strongly enhanced compared to previous InGaAs/InP quantum wires grown in InP V-grooves.

ZnSe crystals have been grown by the travelling heater method (THM) with PbCl 2 as solvent. Our investigations have shown that ZnSe crystals could be obtained with high crystalline perfection referred to a full width at the half maximum (FWHM) down to 20 arcsec of double crystal rocking curves measured at chemically polished (100)-oriented surfaces. Solvent growth techniques like THM should have a remarkable potential for ZnSe bulk growth if the capture of solute as inclusion and precipitation can be avoided.

The present special issue contains a collection of Original Papers dedicated to Professor Johannes Heydenreich on the occasion of his 75th birthday. Johannes Heydenreich, born on 20 June 1930 in Plauen/Vogtland near Dresden, studied physics at the Padagogische Hochschule Potsdam, where he obtained his first academic degree “Dipl. Phys.” in 1958. He received his doctoral degree at the Martin Luther University in Halle in 1961 and the Habilitation degree in 1969. Already during his studies in Potsdam, he showed an interest in electron microscopy due to the influence of his teacher and supervisor Prof. Picht, one of the pioneers in electron optics. His interests were strengthened when Johannes Heydenreich did the experimental work for his Diploma degree at the Institute for Experimental Physics of the University of Halle, where he met Prof. Heinz Bethge for the first time. This was the beginning of a fruitful and longstanding collaboration. In 1962 Johannes Heydenreich joined the team of the later Institute for Solid State Physics and Electron Microscopy of the Academy of Sciences of the GDR, in Halle, for which the basis was laid by Prof. Bethge in 1960. Heydenreich has been working as Assistant Director for many years and played a decisive role in introducing and organising the various techniques of electron microscopy in the institute. The research activities of Prof. Heydenreich covered a broad spectrum over the years. At the beginning of his career he made significant contributions in the field of electron mirror microscopy. After that, his main interests were focused on transmission electron microscopy, ranging from diffraction contrast analysis of crystal defects to high-resolution electron microscopy and image processing. His favourite field was studies of defect-induced phenomena in advanced materials. The so-called Bethge–Heydenreich, the book “Electron Microscopy in Solid State Physics”, published at first in a German edition in 1982 and later in a revised English edition by Elsevier in 1987, provides an excellent overview both of Heydenreich's work and of the spectrum of the Institute of Solid State Physics and Electron Micros-copy in Halle. The international reputation of this institute was the basis for the transformation of it, after the re-unification of Germany, into the Max Planck Institute of Microstructure Physics, the first institute of the Max Planck Society in the Eastern part of Germany. From the beginning, Prof. Heydenreich was on the Board of Directors and served as the Executive Director from 1993 until his retirement in 1995. During this year, the International Centre of Advanced Materials and Electron Microscopy celebrates its 30th anniversary. The Centre was founded in Halle in 1975 as a Centre of Electron Microscopy for the Eastern countries. A remarkable and time-consuming part of Heydenreich's work was associated with this centre. Young scientists from Eastern Europe were trained in the theoretical and practical aspects of electron microscopy during the annual spring and autumn meetings. All in all, Johannes Heydenreich conducted 35 of these schools! From the beginning, he was a member of the Scientific Council of the Centre, and from 1985 until his retirement he was the Director of the Centre. Nowadays, the Centre acts as a real bridge between East and West largely due to the efforts of Johannes Heydenreich. Furthermore, Johannes Heydenreich had been active as a leading member of various scientific boards for many years. He was a co-editor of several journals covering electron microscopy, solid state physics and crystallography. As a member of the Executive Committee of the European Society for Elec-tron Microscopy (CESEM) for many years, and as a member of the Executive board of the German Soci-ety for Electron Microscopy, Johannes Heydenreich has invested a great deal of time and effort in the welfare of the scientific community. Over the course of nearly three decades, Johannes Heydenreich worked as a Professor at the Universities of Halle and Leipzig. Generations of students have admired his excellent lectures with clear repre-sentation and rigorous scholarship. The scientific work of Johannes Heydenreich was honoured by his election to the Academy of Natural Scientists Leopoldina where he worked as a Secretary of Natural Science for many years. The Technical University of Chemnitz conferred an honory doctors degree on Prof. Heydenreich in recognition of his scientific work. The German Society for Electron Microscopy awarded him Honorary Membership. Wolfgang Neumann especially acknowledges with gratitude the time of inspiring collaboration in Halle. All his friends, colleagues, and students wish him many further years of good health. The Editors of physica status solidi join these wishes and add their gratefulness for his long-standing and continuous engagement as a member of the Advisory and Editorial Board of physica status solidi (a).

The title compound is prepared by annealing (350 °C, N2) a system of 28 repetitions of sputtered layer sequences of Ti-Se-Ti-Se-Pb-Se.

The intergrowth compound (SnSe)1.15VSe2 is prepared from the elements by physical vapor deposition using the modulated elemental reactant technique.

The title ferecrystals (fere: Latin, almost) with 1 ≤ n,m ≤ 6 and n and m varied independently are prepared by physical vapor deposition of the elements followed by annealing at 400 °C for 30 min.

We describe an implementation of a general standard basis algorithm, valid for any monomial ordering compatible with the natural semigroup structure. We concentrate on new strategies which have proved useful, in particular in the non-wellordering case. Moreover, we describe the first implementation of Schreyer's method to compute syzygies and compare it with other, more classical methods. Comparisons of the computing time of several examples in the system SINGULAR give hints as to which strategies should be used in different classes of examples.

The atomic structure of nanocrystalline particles formed by vapor deposition and subsequent annealing of amorphous thin films of germanium was studied by high resolution electron microscopy (HREM). The HREM images revealed a strongly varied multiply twinned structure. In some regions of adjacent twins contrast features were detected which were caused by an overlapping of twin lamellae. It will be shown by HREM contrast simulations that these interface types can be described by Σ = 3 n boundaries. The influence of lattice relaxations is taken into consideration by molecular dynamics simulations of the structure models.