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Nanocomposite materials consist of nanometer-sized quantum objects such as atoms, molecules, voids or nanoparticles embedded in a host material. These quantum objects can be exploited as a super-structure, which can be designed to create material properties targeted for specific applications. For electromagnetism, such targeted properties include field enhancements around the bandgap of a semiconductor used for solar cells, directional decay in topological insulators, high kinetic inductance in superconducting circuits, and many more. Despite very different application areas, all of these properties are united by the common aim of exploiting collective interaction effects between quantum objects. The literature on the topic spreads over very many different disciplines and scientific communities. In this review, we present a cross-disciplinary overview of different approaches for the creation, analysis and theoretical description of nanocomposites with applications related to electromagnetic properties. publishedVersion

Design practitioners’ knowledge about Life Cycle Assessment (LCA) is crucial for the necessary decarbonisation of the built environment as well as the mitigation of other negative environmental impacts. Designers’ attitudes towards LCA have so far been rarely analysed. In 2019, as part of the project IEA EBC Annex 72 “Assessing life cycle related environmental impacts caused by buildings”, a global survey was conducted amongst design professionals within 23 countries. The aim was to investigate the level of awareness and acceptance of environmental performance assessment and LCA of buildings, the use of related information sources and tools as well as the application of Building Information Modelling (BIM) in connection to LCA. The results show that less than one third of designers currently provides or uses LCA services. The ones who do not are mainly constrained by the lack of client demand. To support an increased use of LCA during building design, not only it is necessary to provide related data and design/assessment tools, but also to establish standards/regulations to drive client demand. It is particularly relevant to include such requirements already in the client’s brief. In future, an increased demand for building LCA results by institutional investors is expected.

Following cardiac surgical procedures, multiple drainage systems remain in place inside the patient’s chest to prevent the development of pericardial effusion or pneumothorax. Therefore, postoperative bleeding must be diligently observed. Currently, observation of the exudate rate is performed through periodical visual inspection of the reservoir. To improve postoperative monitoring, a measurement system based on load cells was developed to automatically detect bleeding rates. A reservoir retaining bracket was instrumented with a load cell. The signal was digitized by a microcontroller and then processed and displayed on customized software written in LabView. In cases where bleeding rates reach critical levels, the device will automatically sound an alarm. Additionally, the bleeding rate is displayed on the screen with the status of the alarm, as well as the fluid level of the reservoir. These data are all logged to a file. The measurement system has been validated for gain stability and drift, as well as for sensor accuracy, with different in vitro examinations. Additionally, performance of the measurement device was tested in a clinical pilot study on patients recovering from cardiac surgical procedures. The in vitro investigation showed that the monitoring device had excellent gain and drift stability, as well as sensor accuracy, with a resolution of 2.6 mL/h for the bleeding rate. During the clinical examination, bleeding rates of all patients were correctly measured. Continuously recording drainage volume using the developed system was comparable to manual measurements performed every 30 min by a nurse. Implementation of continuous digital measurements could improve patient safety and reduce the workload of medical professionals working in intensive care units.

We report on the effect of pressure on the relaxation modes of the type-A polymer polyisoprene as a function of the chain length for M/Me ratio’s (Me is the entanglement molecular weight): 15, 12, 23, 2, and 5. We find that the spectral shape of the segmental and normal modes is invariant under temperature (T) and pressure (P) variations, but the time–pressure superposition fails as a consequence of the stronger P dependence of the segmental mode. The segmental mode activation volume for the different molecular weights was found to scale with the temperature difference from the respective glass transition temperature. Pressure is found to slow down both modes in a quantitatively similar way, irrespective of the chain length, implying that Me is largely independent of pressure.

We report on the effect of pressure on the dual segmental relaxation of an athermal poly(isoprene-b-vinylethylene) (PI-PVE) diblock copolymer melt using dielectric spectroscopy. The quantity (∂ log τ/∂P)T is employed as a probe of the state of dynamic miscibility in the system. We find that pressure, unlike temperature, induces dynamic homogeneity.

We report on the pressure dependence of the local segmental and normal modes of a type-A polymer (polyisoprene) using dielectric spectroscopy. We find that external pressure exerts a stronger influence on the dynamics of the segmental mode as compared to the longest normal mode which results in the crossing of the two modes at higher pressures. The predictions of the Rouse model are not adequate to explain the different shift factors even at elevated temperatures.

An aliphatic random copolymer ionene (a cationic polyelectrolyte with N + in the repeat unit), was fractionated with the continuous polymer fractionation and investigated for its molecular weight dependent properties. The fractions were analyzed with GPC and capillary viscometry for their molecular weight. Glass transition temperatures were determined with DSC and a strong molecular weight dependence was observed, but no influence in the ionic conductivity was observed. The temperature dependency of ionic conductivity in ionenes is described.

We investigate II–VI optical waveguides consisting of ternary ZnS x Se 1− x and Zn 1− x Mg x Se compounds. The refractive indices are determined experimentally as a function of their composition. A linear interpolation was found to be a good approximation in the case of ZnS x Se 1− x . An empirical relation for Zn 1− x Mg x Se compounds was derived, giving the index of refraction from the band edge to the near infrared for magnesium contents up to 40%. Waveguide modelling is used to optimize waveguides according to the requirements of applications or epitaxial growth. Field distributions and propagation constants of multilayered guiding structures and losses caused by substrate leakage are calculated. Attenuation coefficients of 1–2 cm −1 are measured in waveguides containing ternary II–VI compounds.

The critical thickness anisotropy of the Zn 1-x Mg x Se/GaAs(001) and ZnSe/GaAs(001) systems grown by molecular beam epitaxy (MBE) is investigated by in situ reflection high-energy electron diffraction (RHEED) and transmission electron microscopy (TEM). The increasing FWHM of the specular spot in the RHEED-pattern during growth indicates the initial relaxation stages in strained epitaxial layers as described in an earlier publication [Reisinger et al.. Mater. Sci. Forum 182-184 (1995) 147]. Plan-view TEM-micrographs of ZnSe/GaAs samples show that the perfect 60 -misfit dislocations in the [1 - 10]-direction nucleate prior to the [110]-direction due to their higher mobility. According to the TEM investigation the FWHM increase of the specular spot is connected with the formation of 60 -dislocations perpendicular to the electron beam, whereas dislocations aligned parallel to the beam leave the FWHM unaffected. Finally, a thickness range of the ZnSe-layer from about 225-337 nm is found with misfit dislocations aligned only in the [1 - 1 0]-direction. Furthermore, we present a new in situ RHEED-method to determine the critical thickness of the Zn 1-x Mg x Se/GaAs system separately in both (110)-directions without changing the experimental set-up. The application of this method to various Zn 1-x Mg x Se-samples with different Mg-content x confirms the observation that different critical thicknesses in [110] and [1 - 1 0] are measured related to two different glide systems as observed in ZnSe. Plan-view TEM-micrographs reveal the dislocation structure during the different states of relaxation.

Photoluminescence-excitation (PLE) measurements of wide ZnSe/Zn 1− x Mg x Se single quantum wells (SQW) are presented, performed under high hydrostatic pressure up to 4 GPa. The fully strained samples have been grown by MBE on GaAs(0 0 1) substrates or (1 1 0) substrates. The well transitions 1nH 1s and 1mL 1s with n = 1, 2, 3, 4, 5 and m = 1, 2 were recorded as well as excitonic signals from the barrier material at 2 K and their pressure dependence were determined. A cross-over between the 11L and 13H, as well as between the 12L and 14H transitions, was observed above 1.2 GPa. The transitions were assigned using a modified Kronig Penney model. The exciton binding energy was derived from the energy difference between the 11H 1s and the 11H 2s transitions.

The temperature dependence of the 1s exciton energy has been measured in Zn 1-x Mg x Se epitaxial films at compositions x= 0, 0.07, 0.12, and 0.19 from 2 K up to 280 K. Detailed numerical fits of the individual temperature dependences are provided on the basis of an analytical four-parameter representation developed recently by one of the authors. These are compared with previously used three-parameter models of Vina et al. and Varshni. The x-dependence of the exciton energy, E 1s (T, x), and of the fundamental band gap energy, E g (T, x), is given to very good approximation by linear functions of the composition x for any T from absolute zero up to room temperature. A comparison with recent room temperature band gap energy data by Jobst et al. shows that this linear dependence holds up to x0.7. The magnitudes of the model-dependent empirical parameters, which control the temperature dependence of the band gap energy in different compounds, are found to change significantly with increasing magnesium content. From the magnitude of the effective phonon temperature, particularly in the case of ZnSe, we conclude that the main contributions to the band gap shrinkage effect are due to acoustic phonons.

Two amines, Et3N and tBuNH2 have been investigated in their role to improve the quality of MOVPE-grown ZnSe layers. A reduction of growth rate is observed in the kinetic limited range, which is shown to be due to an increase of activation energy, independent of the amine used. An improvement of the layer quality is related to the suppression of nonradiative recombination centers. However, 2D growth, controlled by ex situ RHEED and MBE-regrowth experiments, was only observed without Et3N. Under photoirradiation the growth rate increases in the kinetic limited range, where the two amines show remarkable differences. Whereas in this case tBuNH2 leads to a poor optical layer quality, Et3N gives excellent layers at sufficiently high growth rates. The experiments, including RDS growth control, lead to the conclusion that the nitrogen compounds are always adsorbed at Se-terminated surfaces and thus inhibit a quick reaction of Zn and Se on the surface. A model is proposed which describes the presented experiments consistently.

We present optical measurements of freestanding thin Zn1−xMgxSe films and of a ZnSe/Zn0.93Mg0.07Se single quantum well (SQW) under hydrostatic pressure applied by a diamond anvil cell. For the Zn1−xMgxSe compounds the pressure shift of the fundamental gap was determined from absorption measurements at room temperature for X ⩽ 0.37. A hydrostatic deformation potential a(x) = −4.85 + 0.67x eV is derived. The transition pressures Ptr to high pressure phases were determined by visual observation. The pressure dependent absorption and photoluminescence of the ZnSe SQW was investigated at 2 K. The energy shift of two SQW-related transitions was recorded and is reproduced by a simple theoretical model. LO-phonon replica were visible in photoluminescence at the sharp 11hh transition.

MBE-grown ZnCdSe ZnSe and MOVPE-grown ZnSe ZnSSe single quantum wells (SQW) were investigated by photoreflectance (PR) and photoluminescence excitation (PLE) spectroscopy. For various compositions a set of quantum well structures with different well thicknesses was grown. The PR spectra exhibit sharp signatures of which the transition energies have been accurately determined by a line shape fit. The peaks in the PLE spectra and correspondingly the PR signatures can be attributed to ground and excited excitonic states by comparison with the excitonic absorption model of Toyozawa. With an envelope function formalism including all strain effects a fitting procedure was developed which allows the evaluation of the band alignment. This procedure overcomes the problems of the uncertainties in the hole masses by simultaneously fitting all the transitions observed at one composition by varying also the hole masses. It is the accurate knowledge of the structural parameters of the samples and the precise determination of the transition energy which gives the composition dependent offset a high reliability.

ZnCdSe ZnSe quantum wells (QW) were grown with molecular beam epitaxy (MBE) on GaAs(001) substrates cleaned with hydrogen plasma. Reflection high-energy electron diffraction (RHEED) was used for in-situ growth control of the QW structures. A quantitative evaluation of the RHEED oscillations yields an exact value of the growth rate. Furthermore, in comparing the growth rate of the barrier and the well a reasonable estimate of the Cd content is possible. The in-situ RHEED measurements were supplemented by ex-situ HRXRD and HRTEM investigations. The latter method was found to be especially useful to evaluate the Cd-concentration profile of the QWs by digital analysis of lattice images (DALI). X-ray rocking curves of MQWs were recorded which show well-resolved satellite peaks. A comparison with simulations based on dynamical diffraction theory yields the structural parameters such as well width, barrier width and composition of the QWs. The XRD and TEM results are compared with the parameters determined by RHEED. In addition, we performed photoluminescence (PL) and photoluminescence excitation (PLE) spectroscopy for optical characterization of the samples. The PLE spectra show an interference pattern which is explained by standing polariton waves.

We have observed “dark resonances” in theA-type level structure, formed by the 4S1/2 ground state, the 4P1/2 excited state and the low lying metastable 3D3/2 state in the Calcium ion, confined in a Paul radio-frequency trap. These Doppler-free and potentially very narrow resonances were used to determine the magnetic dipole hyperfine interaction constant A for the 4P1/2 and 3D3/2 state of43Ca+, giving −142(8) MHz and −48.3(1.6) MHz, respectively. From measurements of the P-D (E1) and S-D (E2) transition wavelength in a mixture of43Ca+ and40Ca+ we determined the isotope shifts of these lines.

In this work, we report on resonant photoluminescence (RPL) investigations of epitaxially ZnSe GaAs layers grown by MBE and MOVPE. Lattice mismatch between ZnSe and GaAs causes a strain in the layer material which is relaxed by nucleation of misfit dislocations during growth. The relaxation process depends on layer thickness and growth conditions. Different thermal expansion coefficients of ZnSe and GaAs lead to a further strain component when the samples are cooled to RT or 2 K. The resulting compressive or tensile strain causes a splitting of exciton states and a shift of exciton recombination energies to higher and lower energies respectively. The strength of this shift depends on the ¦m j ¦ value of holes. We determine the recombination energy of free and bound excitons for different strain conditions (from fully relaxed ZnSe GaAs layers to samples without any strain relaxation) with interband excitation. The resulting deformation potentials are compared to results from measurements with high pressure diamond cells. Additionally, these investigations enable us to identify donor and acceptor bound excitons in biaxially strained ZnSe GaAs layers as heavy or light hole exciton states for compressive or tensile strain respectively. The characteristic binding energies of Cl-donors are investigated with RPL. A comparison of transition energies from the ground state to excited states indoped and undoped materials allows an identification of impurities in as-grown ZnSe. The ground state energy of N-acceptors is determined by temperature dependent measurements. Binding energies of Cl-donors and N-acceptors in biaxially strained ZnSe GaAs layers are compared to their corresponding energy levels in strain-free ZnSe. The strain in the layer lowers the symmetry of acceptor states and changes their binding energy. Excited acceptor states are again investigated by RPL measurements.

The diffusion coefficient D(T) of Cd in CdSe ZnSe single quantum well (SQW) structures grown pseudomorphically on GaAs(001) is determined by high resolution transmission electron microscopy of annealed SQWs and subsequent digital analysis of lattice images. SQWs of 2 monolayer (ML) thickness were grown by molecular beam epitaxy. During growth the CdSe quantum wells (QWs) broaden to about 7 ML CdZnSe as measured by reflection high energy electron diffraction (RHEED). We find for the diffusion coefficient of Cd in ZnSe at temperatures between 340 and 400° C D(T) = 1.9 × 10−4 [cm2/s] · exp(− 1.8 [eV]/kT).

In this work, we report on the dependence of strain relaxation in epitaxially grown ZnSe GaAs layers on the growth process. New investigations about luminescence signals are presented, which are caused by lattice defects in these layers. The strain is due to different lattice constants of layer and substrate material and is relaxed by the nucleation of misfit dislocations during growth. This relaxation process depends on layer thickness and growth conditions. We determine the residual strain for different layer thicknesses and growth processes with X-ray diffractometry. Furthermore, the created misfit dislocations give rise to a luminescence at 2.6 eV, the so-called Y line. We found that its behaviour in ZnSe is analogous to that of Y lines in epitaxially grown ZnTe GaAs layers. An excitation of the Y luminescence is only possible with photon energies higher than the recombination energy of free excitons. Its intensity decreases with increasing impurity concentration. It also decreases strongly for a steady state excitation at 2 K. A recovery effect of luminescence intensity is observed, if the sample is heated to room temperature. Furthermore, the strain dependence of the Y luminescence in ZnSe is compared with the maxima of bound exciton luminescence from shallow donors and acceptors.

Single-crystalline ZnSe layers were grown by metal-organic vapour phase and molecular beam epitaxy on (001) oriented GaAs substrates. The lattice mismatch between layer and substrate at growth temperature causes a strain in the layer material, which is relaxed by the nucleation of misfit dislocations. The relaxation process starts at the critical thickness, which depends on the growth conditions. The crystalline quality and the residual strain of the epilayers were investigated with a high-resolution X-ray diffractometer. Additionally, the intensity distribution of the scattered X-rays in the directions perpendicular and parallel to the reciprocal lattice vector (004) was observed by a two-reflection analyser crystal. For the system ZnSe/GaAs, this intensity distribution depends on the degree of strain relaxation, which is dependent on the layer thickness. The results are compared with transmission electron microscopy results.

The properties of ZnSe-based heterostructures on (001) GaAs substrates grown by metalorganic vapor phase epitaxy (MOVPE) are compared with those grown by molecular beam epitaxy (MBE). The structural and optical properties are examined with high-resolution X-ray diffraction (HRXRD) and photoluminescence (PL). Furthermore the results of C–V measurements of p-ZnSe layers doped with nitrogen are discussed and I–V characteristics and electroluminescence (EL) spectra of LEDs grown with both techniques are presented. ZnSe/Zn(SSe) MQWs are prepared with MOVPE and (ZnCd)Se/ZnSe MQWs with MBE to improve the optical efficiency of the diodes.

The crystalline structure, surface morphology, optical properties and purity of ZnTe layers grown by MOVPE were investigated. Various substrates, different combinations of metalorganics and various growth conditions were studied. The results of three different MOVPE growth systems and reactor cells are compared. A variety of methods were used to study the structure and morphology (e.g. TEM, HRTEM, X-ray diffraction, Nomarski microscopy, photo reflection, Raman scattering). The preparation of the GaAs and ZnTe surfaces is well advanced but problematic for GaSb. For heterostructures like ZnTe on GaAs (001) with about 7% mismatch, the crystalline structure is mainly dominated by interfacial misfit dislocations and threading dislocations penetrating about 300 nm into the ZnTe layer. With better matched substrates (GaSb or ZnTe) or different orientations (GaAs (111)), the threading dislocations can nearly be eliminated. The comparison of growth studies with MOVPE, MBE and ALE reveals that the initial growth of ZnTe on GaAs (001) is mainly determined by the misfit and its relaxation. The first ≈4 monolayers are characterized by a pseudomorphous, 2D growth mode. The following surface roughening is caused by a relaxation through a 3D growth mode with islands. Once the relaxation is completed, the surface smoothens and recovers the 2D growth mode. The initial growth stages, representing the Stranski-Krastanov mechanism, are dependent on the surface termination of the substrate and on the growth method and parameters. The surface morphology of thicker ZnTe layers (>0.1 μm on GaAs (001)) grown by MOVPE is solely determined by the conditions at the growing interface (adsorption and decomposition of the precursors, desorption of undesired species, quantities of released Zn and Te, surface stoichiometry). These interface conditions are dependent on the precursor combination, the kinetic or mass transport limitation and the reactor hydrodynamics. The studies of the layer properties were sometimes bothered by a thin native oxide with the structure ZnTe/Te/ZnO. Purity and optical quality were tested by low temperature PL. The strain induced by the cooling of the ZnTe/GaAs structures grown at 300–400°C renders the identification of the radiative transitions difficult. However, many transitions and radiative centers are now identified. Under many growth conditions, the (A0Asl, X1) transition which is due to As from substrate autodoping, dominates the spectra. Hence, stoichiometry and inhomogeneity of the GaAs substrates are reflected in the spectra. But also precursor combination, partial pressures and growth temperatures have a significant influence on the PL spectra. The substrate type (GaAs, GaSb, ZnTe) is reflected in the spectra by transitions due to outdiffusion and by the Y-lines which are related to the misfit dislocations. Transitions induced by layer contaminations like Cu, Li, O and N were found. With the alkyl combination DEZn/DIPTe, reproducible growth of samples is possible showing PL spectra dominated by free excitons. The frequently appearing I1c and I'1c transitions might be due to a VZn vacancy or a vacancy donor complex. Complex relations to the growth stoichiometry were found. SIMS measurements helped to further identify the layer impurities. The layer purity is affected by extrinsic impurities due to substrate outdiffusion (As, Ga), contaminations from growth system (O, Cu) and precursors (Li). Impurities like H and C (and N) which are intrinsic to the MOVPE process, depend on the dissociation kinetics of the precursors which are themselves dependent on the growth parameters (e.g. temperature, carrier gas). The origins of the extrinsic impurities are identified as far as possible.

Two strong emission bands (Y1 and Y2), 210 and 250 meV lower than Egap of ZnTe, have been studied in heteroepitaxially grown ZnTe layers. The phonon coupling and the thermalization energy of these emissions are usually small, similar to those of the Y band in ZnSe and CdTe layers. The Y luminescence in ZnTe is emitted above all near the ZnTe/GaAs interface which contains a high density of lattice defects (mainly misfit dislocations). An increasing concentration of point defects leads to a strong decrease of the Y emission. The observation of this luminescence in ZnTe bulk material or in homoepitaxially grown ZnTe is not possible because of a strong dependence of the intensity on the defect concentration and the dislocation density. Both bands are excited only by laser light resonant to or higher than the free exciton energy. The strain dependent energy shift behaves similar to that of bound excitons. The intensity of the Y bands observed at liquid helium temperature decreases under strong laser excitation. A recovery effect of both lines is observed when the sample is heated to liquid nitrogen or room temperature.

The near-gap photoluminescence (PL) of MOVPE ZnTe epilayers grown on (0 0 1) GaAs substrates has been extensively studied using resonant-excitation methods. Heteroepitaxial ZnTe layers show a small biaxial strain which splits excitonic transitions. We obtained the Luttinger parameter γ1 = 3.8 from transition of the split free exciton 1s and 2s levels. Shallow acceptor states were observed in free standing As- and P-doped ZnTe layers and the Luttinger parameters γ2 = 0.72 and γ3 = 1.3 were derived. The magnetic field splitting of the 1S 3 2 acceptor ground state unambiguously identifies the acceptor bound exciton line I1a as double light-hole state (A0a1, X1). Furthermore the magnetic parameters κA = -0.27 and qA = -0.015 were determined.

Two new strong deep emission bands with a weak phonon coupling were observed in heteroepitaxial ZnTe layers. The study of PL, PLE spectra in the layers with different thicknesses has shown that these emissions are produced in the ZnTe/GaAs interface region. It is suggested that the observed luminescence is related to the recombination of excitons bound to some extended structural defects, probably misfit dislocations. An unusual behavior of these bands - PL ‘fatigue’ effect - was observed under the strong laser excitation.

We analysed 20 boxes of, frozen imported bait-shrimp (China: Parapenaeopsis sp. and Metapenaeopsis sp.) and 8 boxes of native, frozen bait-shrimp (Gulf of Mexico: Litopenaeus setiferus and Farfantepenaeus duorarum) by RT-PCR or PCR for Taura syndrome virus (TSV), yellowhead virus/gill-associated virus (YHV/GAV), white-spot syndrome virus (WSSV) and infectious hypodermal and hematopoietic necrosis virus (IHHNV). All 28 boxes of shrimp were negative for TSV, YHV/GAV and IHHNV; 2 boxes of imported bait-shrimp were WSSV-positive by 3 different PCR assays. Intramuscular injection of replicate groups of SPF (specific pathogen-free) L. vannamei juveniles with 2 different tissue homogenates prepared from the 2 WSSV-positive bait boxes resulted in 100% mortality of the test shrimp within 48 to 72 h post-injection. No mortality occurred among injected negative control groups. Histological and in situ hybridization analyses of 20 moribund treatment-shrimp demonstrated severe WSSV infections in each sample. Oral exposure of SPF L. vannamei postlarvae, PL (PL 25 to 30 stage; approximately 0.02 g) to minced tissue prepared from the 2 WSSV-positive bait-lots did not induce infection, possibly because of an insufficient infectious dose and/or viral inactivation resulting from multiple freeze-thaw cycles of the bait-shrimp during PCR testing. Use of an electric drill and collection of drill-tailings (tissue from approximately 20 to 30 shrimp) from frozen blocks of shrimp was successfully employed as an alternate tissue-sampling method without thawing. Our findings indicate that imported WSSV-infected bait shrimp, originating from China, are being sold in Texas for the purpose of sport fishing and represent a potential threat to freshwater and marine crustacean fisheries, as well as to coastal US shrimp farms.

Under an excitation density of 0.4 W/cm2, a strong biexcitonic peak was observed in the photoluminescence (PL) spectrum of a single quantum well which was grown in submonolayer deposition mode. Its intensity was found to increase superlinearly with excitation density. The shape of the biexcitonic peak was found to be similar to that of biexcitons in CuCl and CdS crystal and a binding energy of 9.8 meV was obtained. When the temperature increased from 10 to 31 K, the biexcitonic peak decreased considerably whereas the excitonic peak increased slightly.

Interference pattern due to standing polariton waves have been observed in thin planparallel ZnSe layers. The samples consist of pseudomorphic ZnSe/ZnCdSe quantum well structures grown by molecular beam epitaxy with cap layers of various thicknesses. The interference pattern appearing in reflectance and photoluminescence excitation spectra were fitted to calculated spectra applying a simple theoretical model. This fit results in the determination of the deadlayer thickness and the evaluation of the Luttinger parameter γ1 and γ2.

A single-chip CCD image sensor captures >100 successive images at >1 Mframes/s. The pixel count of the test chip is 312/spl times/260 (=81,120) pixels. Charge handling capacity is 40 k electrons. Grey levels are 10 b. Fill factor is 13%. An on-chip overwriting mechanism makes possible continuous recording of the latest image signals, draining the old ones to the substrate.

Two sharp and intense emission bands with the maxima of 2.185 and 2.150 eV and a weak phonon coupling were investigated in the heteroepitaxial ZnTe layers. The study of the ZnTe layers grown on different substrates with thicknesses of 0.5–3.2 μm has shown that this luminescence is produced in the interface region that contains a high density of structural defects. The temperature dependence of these bands reveals the excitonic character of the recombination. We propose that the observed bands originate from the recombination of excitons localized at structural defects such as dislocations and associated defects.

This paper gives an overview of advanced scheduling and dispatching policies for WIP (work in process) management within the wafer fabrication process. Additionally, the pros and cons of general WIP control philosophies are opposed. Several control policies are evaluated for the application in complex make-to-order environment such as ASIC production. Based on the real shop floor environment of Philips SMST and the currently used control policies a proposal is presented answering the following two questions: what are the requirements of tomorrow's WIP control systems applied in make-to-order wafer fabrication; and how can these control policies be implemented and introduced on the shop floor using existing WIP control and scheduling systems?.

We report on the experimental and theoretical study of the strain splitting of nitrogen acceptor levels in epitaxially grown ZnSe on GaAs substrate. The crystal strain is due to the different lattice constants and thermal expansion coefficients and is determined by x-ray diffractometry. The binding energies of the acceptor ground and excited states have been determined by temperature-dependent and resonant photoluminescence measurements involving two-hole transitions for three differently strained levels. A consistent theoretical description of the experimental data is given in terms of the model of Baldereschi and Lipari, augmented by the Bir-Pikus Hamiltonian to account for the strain splitting of the valence-band edge. An empirical ansatz for the central-cell correction is used in order to reproduce the chemical shift of the nitrogen acceptor.

We report on reflected high‐energy electron‐diffraction and transmission electron microscopy plane‐view investigation of the dislocation structure in doped and undoped ZnSe/GaAs(001) grown by molecular‐beam epitaxy and metal‐organic vapor‐phase epitaxy. The thicknesses of the investigated layers vary between 60 and 900 nm. Several stages of dislocation formation are found which occur at distinct layer thicknesses. Frank partial dislocations (up to 500 nm), Shockley partial dislocations (between 130 and 400 nm) with a maximum density at 300 nm, and perfect 60° dislocations (above 300 nm) are observed in samples with perfectly smooth surface. The formation of Shockley partial dislocations is strongly anisotropic which might be due to the higher mobility of α‐type dislocations. An increased roughness of the growing surface yields a suppression of Shockley partial dislocations and an irregular dislocation network with dislocations inclined to the 〈110〉 directions. A regular dislocation network with straight dislocations is found in Cl‐doped samples.

We investigate the transient four-wave mixing (FWM) response of wide ZnSe/Zn 1- xMg xSe single quantum wells in a two-beam self-diffraction configuration. The spectrally resolved FWM signals show excitonic transitions which are essentially homogeneously broadened, and show dephasing times between 1 and 2 ps at a lattice temperature of 10 K. Simultaneous excitation of several exciton states leads to pronounced quantum beats in the FWM signal. The formation of heavy-hole biexcitons with binding energies of E bXX = 3.5 ± 0.5 meV is identified by polarization-dependent measurements. These measurements also indicate that excitation-induced dephasing gives the main contribution to the FWM process.