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Ein 49-jahriger Patient stellt sich in einer Spezialklinik fur arthroskopische Chirurgie und Sportmedizin mit Schulterschmerzen vor. Dort gibt er an, dass ihn die rechte Schulter seit den fruhen 1980er-Jahren immer wieder schmerze. Da er nie korperlich gearbeitet habe und auch recht unsportlich sei, habe er sich mit der Situation lange Zeit arrangiert. Die Schulter fuhle sich nun aber schon seit Jahren „instabil“ an. Er habe sie jedoch nie ausgekugelt, noch sei er je in einer arztlichen Behandlung betreffend der Schulter gestanden. Da er seit einigen Monaten vermehrt eine schwere Aktentasche tragen musse, store ihn die Schulter nun aber im Alltag. Es stelle sich fur ihn die Frage, ob dies nicht behandelt werden konne.

Angle dependent X-ray emission spectroscopy (AXES) is introduced as a tool for depth dependent composition analysis. A controlled variation of the information depth is demonstrated by changing the geometry from grazing exit to grazing incidence geometry. First results are presented from Cu(In,Ga)Se 2 (CIGSe)-based polycrystalline thin film solar cell bi-layer components. A mathematical model explains changes in relative intensity due to the absorption and emission behavior of thin CdS and Zn(S,O) cover layers. The fact that the presented data can be modelled by ideal bi-layer structures, provides both, proof of concept in general and the proof of applicability to the relatively rough layered structures based on CIGSe. In bare CIGSe a homogeneous distribution of Cu and Ga is found in a depth range between 22 and 470 nm.

We investigated energy-transfer processes in a bridged organic donor–acceptor dyad system of triphenyldiamine and perylenebisimide using time-resolved and fluorescence emission spectroscopy. The fluorescence lifetimes of the isolated model components and their mixtures have been determined as a function of the concentration of the chromophores. Subsequently, energy-transfer experiments were conducted in solutions of free donors, free acceptors and their mixtures. The results of these experiments are in reasonable agreement with predictions based on Forster theory. Finally, experiments were performed on a donor–acceptor system covalently bound by a C12H24-linker.

We present a joint experimental and theoretical study of the electronic structure of the chain compounds A1 − xCuO2 (A=Ca,Sr,Ba) using O-K and Cu-L3 X-ray absorption spectroscopy. The doping-dependent behaviour in these systems differs from that of conventional 2D Cu-O networks formed by corner-shared CuO4 plaquettes. It follows from the strongly weakened inter-plaquette hybridisation due to the nearly 90deg Cu-O-Cu bond in the chains. Spectroscopically, this results in a) the different final states in the Cu-L3 spectra which can be used directly to "read-off" the Cu valency and b) a drastic reduction in the dynamic spectral weight transfer from the upper Hubbard band to the low-energy scale in the O-K spectra.

The electronic structure and the valency of the Sc ions in the endohedral dimetallofullerene ${\mathrm{Sc}}_{2}@{\mathrm{C}}_{84}$ with ${D}_{2d}$ symmetry are probed using high-energy spectroscopy. Comparison of the Sc $2\stackrel{\ensuremath{\rightarrow}}{p}3d$ x-ray-absorption spectrum with calculated ionic multiplet spectra shows that the Sc ions are trivalent. Detailed multiplet calculations including covalency indicate that the effective valency of the Sc(III) ions can be described by a formal charge transfer to the fullerene cage of $2.6\ifmmode\pm\else\textpm\fi{}0.1.$ This illustrates that a purely ionic picture is not valid for the electronic structure of ${\mathrm{Sc}}_{2}@{\mathrm{C}}_{84},$ and that a more complex picture including finite hybridization between the Sc and the fullerene cage has to be applied.

The microscopic structure of the P-rich (2×1)-like surfaces of InP(001) is investigated by soft X-ray photoemission spectroscopy (SXPS) and scanning tunneling microscopy (STM). The samples were grown by metal organic vapor phase epitaxy (MOVPE) and then transferred under ultra high vacuum (UHV) conditions to UHV analysis chambers. STM images show a P-rich as-grown surface after transfer and another less P-rich surface after prolonged annealing at 350°C. The In4d emission line is not affected by the change in surface reconstruction and shows a small surface component shifted by 0.48 eV towards higher binding energies. The line shape of the P2p core level, on the other hand, changes: On the as-grown surface, one surface component which is shifted by 0.98 eV towards higher binding energies is found after transfer, whereas two surface components shifted to higher and lower binding energies, respectively, appear after annealing at 350°C. These results are consistent with the structure models derived from STM for the different P-rich (2×1)-like surfaces.

Rayleigh-B\'{e}nard convection in horizontal layers of binary fluid mixtures heated from below with realistic horizontal boundary conditions is studied theoretically using multi-mode Galerkin expansions. For positive separation ratios the main difference between the mixtures and pure fluids lies in the existence of stable three dimensional patterns near onset in a wide range of the parameter space. We evaluated the stationary solutions of roll, crossroll, and square convection and we determined the location of the stability boundaries for many parameter combinations thereby obtaining the Busse balloon for roll and square patterns., Comment: 19 pages + 15 figures, accepted by Journal of Fluid Mechanics

We investigate the lineshape of In4d and P2p core level emission spectra recorded with high spectral resolution on cleaved InP(110) surfaces for a wide range of photon energies. A curve fitting analysis with Voigt functions is used to decompose the spectra in surface and bulk core level emission lines. We find that an intrinsic broadening of approximately 250 meV limits the linewidth of the In4d and P2p emission components of both surface and bulk. We attribute the broadening to local band bending variations induced by surface inhomogeneities such as cleavage steps and atomic defects. Surface core level shifts of 320 meV for In4d and 305 meV for P2p are found, in excellent agreement with previously published data. The intensity of the surface components with respect to those of the bulk is found to deviate from the expectation based upon the electron escape depth due to photoelectron diffraction effects.

During the 1996 lead run time, CERES has accumulated 42 million events, corresponding to a factor of 5 more statistics than in 1995 and 2.5 million events of a special photon-run. We report on the results of the low-mass e$^+$e$^-$-pair analysis. Since the most critical item is the poor signal-to-background ratio we also discuss the understanding of this background, in absolute terms, with the help of a detailed Monte Carlo simulation. We show preliminary results of the photon analysis and summarize the results of the hadron analysis preliminarily reported on already at QM'97, 10 pages, 9 figures, Proceedings of the XIV Int. Conf. on Nucleus-Nucleus Collisions,Quark Matter 99, Torino, Italy, May 10 - 15, 1999

We present high-energy spectroscopy results on the occupied and unoccupied electronic structures of the strongly anisotropic compounds ${\mathrm{MoO}}_{3}$ and ${\mathrm{K}}_{0.3}{\mathrm{MoO}}_{3}$ near the Fermi level. X-ray photoemission reveals a close similarity of the valence-band spectra in both materials. The metal ${\mathrm{K}}_{0.3}{\mathrm{MoO}}_{3}$ shows an additional Mo $4d$-derived conduction band whose population is achieved by electron transfer from K to Mo. This is concluded from studies on intentional surface doping of insulating ${\mathrm{MoO}}_{3}$ which leads to the occurrence of Mo $4d$-like defect states near the Fermi level. Information on the unoccupied states and their orbital symmetries was obtained by polarization-dependent x-ray absorption spectroscopy. These experiments confirm previous descriptions of the electronic structure in terms of a molecular-orbital picture. For ${\mathrm{K}}_{0.3}{\mathrm{MoO}}_{3},$ strong local Mo $4d\ensuremath{-}\mathrm{O}$ $2p$ bonding is not only found along the chain direction but also perpendicular to it. This finding is reminiscent of earlier band calculations, which found the chains to form pairs by pronounced transverse hybridization, with the overall bandwidth remaining one dimensionally anisotropic. This adds an important aspect to the discussion on possible Luttinger-liquid physics in the low-dimensional Mo bronzes.

The CERES/NA45 experiment at the CERN-SPS is dedicated to study the production of e + e − -pairs in ultrarelativistic heavy ion collisions. Compared to extrapolations from results obtained in proton-induced reactions, it has previously observed an enhanced production in S-Au [1] and Pb-Au [2] collisions. To verify this enhancement and to study its properties, higher statistics were accumulated during a runtime in 1996. We report here, for the first time, on the results of this analysis (for details see ref. [3]).

The fifteenth conference in the Vacuum Ultraviolet Radiation Physics series (VUV XV) took place in Berlin, Germany, from July 29th to August 3rd, 2007. This conference series began in 1962 in Los Angeles with the aim of encompassing theoretical as well as experimental studies of the interaction of ultraviolet and soft X-ray radiation with matter. In this year's VUV conference, more than 520 participants from 32 countries gathered in the Konzerthaus am Gendarmenmarkt, a famous concert hall right in the historic center of Berlin, to report on their scientific results and to meet old friends. The conference program consisted of 89 plenary, invited and contributed talks. Since young scientists are the target audience of the VUV-series, more than 450 contributions were presented as posters.

Normal-emission photoelectron spectra were recorded from W(110) using photons in the energy-range $11\mathrm{}\mathrm{eV}l~\mathrm{\ensuremath{\Elzxh}}\mathrm{\ensuremath{\omega}}l~30\mathrm{}\mathrm{eV}.$ The results are discussed in comparison to available band-structure calculations and experimental data obtained in earlier studies. We find reasonable overall agreement and summarize a set of ``best'' critical-point energies along the $\ensuremath{\Gamma}\ensuremath{-}\ensuremath{\Sigma}\ensuremath{-}N$ direction of the bulk Brillouin zone, both below and above the Fermi energy.

Convection structures in binary fluid mixtures are investigated for positive Soret coupling in the driving regime where solutal and thermal contributions to the buoyancy forces compete. Bifurcation properties of stable and unstable stationary square, roll, and crossroll (CR) structures and the oscillatory competition between rolls and squares are determined numerically as a function of fluid parameters. A novel type of subharmonic bifurcation cascade (SC) where the oscillation period grows in integer steps as $n (2\pi)/(\omega)$ is found and elucidated to be an entrainment process., Comment: 7 pages, 4 figures

Hadronic spectra from interactions of Pb on Au at 158 AGeV/c have been measured by the CERES experiment at the CERN SPS. We report on preliminary results on transverse mass spectra of identified pions and negative hadrons as well as spectra of the positive charge excess obtained by subtracting the negative particle distribution from that of positive tracks. We have also performed a study of the event azimuthal anisotropies which give evidence for directed and elliptic flow in non-central collisions.

The CERES/NA45 collaboration measured, at the CERN SPS, low-mass electron pair production in Pb Au collisions at 158 A GeV/c incident momentum. In this paper we present an analysis of the data taken during the SPS Pb-beam period in the fall of 1995. The results confirm previous findings of CERES showing that the pair production in the mass range 0.2 ee 2 , when scaled to the ion case with the event multiplicity, is enhanced over the expected yield from the known hadronic sources in pp collisions. A comparison of the results for different multiplicity bins indicates that the excess increases faster than linearly with charged-particle multiplicity. We also present the transverse-momentum distributions of the observed pairs.

The carbon $1s$ core levels of diamond (100) and (111) surfaces were investigated using high-resolution photoelectron spectroscopy. The surfaces were prepared in a hydrogen plasma, which is known to result in atomically flat surfaces. From the signature of the C $1s$ core-level spectra, four different surface terminations can be distinguished. The as-prepared surfaces exhibit a surface component shifted by $+0.5$ to $+0.8\mathrm{eV}$ toward higher binding energy, which we assign to multiple termination of carbon atoms by hydrogen. Annealing these surfaces first results in the development of the surfaces terminated monoatomically by hydrogen. A small chemical shift of $\ensuremath{-}0.15\mathrm{eV}$ was deduced for the hydrogen-terminated surface atoms of the (111):H surface with respect to the bulk carbon atoms. Further annealing leads to spectra characteristic for hydrogen-free, reconstructed diamond surfaces. This process is shown to be thermally activated with an activation energy of $3.4\ifmmode\pm\else\textpm\fi{}0.4\mathrm{eV}.$ The corresponding chemical shifts between surface and bulk components vary between $\ensuremath{-}0.78$ and $\ensuremath{-}1.15\mathrm{eV}$ depending on surface orientation and surface treatment. Finally, annealing at $T\ensuremath{\approx}1250\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ leads to a partially graphitized surface for diamond (111) while on the diamond (100) surface a $4\ifmmode\times\else\texttimes\fi{}1$ reconstruction is observed. The sign and magnitudes of the chemical shifts are discussed.

We present a detailed joint experimental and theoretical investigation of the valence band electronic structure of single crystals of the model cuprate Ba2Cu3O4Cl2. This oxychloride system possesses a Cu3O4 plane which can be regarded as a superposition of two subsystems: a Cu AO 2 cuprate plane and an extra Cu B site, and thus represents an ideal trial system for assessing the impact of deviations from the CuO2 plane stoichiometry upon the electronic structure in cuprate materials. From polarization-dependent, k-resolved photoemission measurements the dispersion relations and symmetry of a number of the observed valence band features are determined and compared with the results of band structure calculations carried out within the LSDA1U formalism, which include a detailed analysis of the character and symmetry of the individual bands. Upon electron removal, the extra copper site makes its presence felt via the formation of a second Zhang-Rice singlet located on the Cu B subsystem, in addition to that originating from the CuAO2 subsystem. The main valence band edge at ;2 eV binding energy is shown to be mainly due to bands involving combinations of O 2px ,y orbitals, some of which exhibit essentially pure O 2p character. These low-lying oxygen bands are different in origin from the nonmixing O 2p states observed, for example, at (p ,p) in Sr2CuO2Cl2, as the orbital combination responsible for the latter is involved in Ba2Cu3O4Cl2 in the formation of the Zhang-Rice singlet state on the CuB sublattice. @S0163-1829~98!00717-6#

using photoemission and electron energy-loss spectroscopy in transmission. In particular, the impact of the isomer symmetry of the C82 cage (Cs or C3v) on the electronic structure and on the optical properties is analysed in detail. For both isomers, combined XPS and XAS measurements of the Tm 4f and 4d states offer conclusive proof of a divalent encaged Tm ion. No significant change of the valence of the rare earth ion upon changes in the cage symmetry is observed. From the C 1s excitation spectra we find a more pronounced LUMO for the C3v(8) isomer, as is expected for the higher symmetry of the cage. Additional information about the optical properties was obtained from the low-energy loss function. With use of a Kramers–Kronig analysis, the dielectric function, e, and the optical conductivity, σ, have been derived. e(0) and the onset of the spectral weight are found to be 7.7 [12.8] and 0.6 eV [0.8 eV] for the Cs(6) {C3v(8)} isomer, respectively.

The interface formation of Zn/CdTe(100) has been investigated using synchrotron and Mg $K\ensuremath{\alpha}$ x-ray photoelectron spectroscopy. We identify five distinct phases of the interface formation process, including the passivation of surface defects by small amounts of adsorbed Zn $(l~$ 0.1 \AA{}), diffusion of Zn into Cd vacancies and lattice-site defects, and a Cd-Zn exchange, thus forming the ternary compound ${\mathrm{Cd}}_{1\ensuremath{-}x}{\mathrm{Zn}}_{x}\mathrm{Te}$ in a near-surface region. In the final stage of the indiffusion, we find significant Cd segregation and also, to a smaller extent, Te segregation. The formation of a metallic Zn overlayer for high Zn coverages is associated with a surface photovoltage effect at room temperature. The results derived from the investigation of Zn-induced band bending, surface core-level shifts, and peak area evaluations are discussed, and a model based on the variation of the photoemission information depth is given. We also present a simple method to determine the onset of Cd segregation in order to identify the ternary ${\mathrm{Cd}}_{1\ensuremath{-}x}{\mathrm{Zn}}_{x}\mathrm{Te}$ surface-alloy with maximum Zn content.

We report preliminary results of the first measurement of low-mass electron pairs in 160 GeV/nucleon PbAu collisions at central rapidities in a wide multiplicity range. This work is the continuation of our systematic studies on pair production in p-Be, p-Au and SAu interactions. The motivation for this effort derives from a new source of lowmass dileptons recently observed in SAu and S-W collisions by CERES and HELIOS/3, respectively. The results obtained in the analysis of the PbAu data confirm our previous finding that pair production in the mass range 0.2 < mee < 1.5 GeV/c2 is enhanced over the contributions from hadron decays while no significant excess could be observed for mee ≲ 2mπ. A comparison of the results for different multiplicity bins favours a non-linear dependence of the e+e−-yield on the accompanying charged particle densities.

Angle resolved photoemission spectroscopy with synchrotron radiation was used to study the valence band structure of InSb (100). Normal emission energy distribution curves exhibit direct transitions from the valence band maximum Γ8 at the Γ-point of the Brillouin zone and along the [100] direction (Δ). The splitting of the valence band maximum along Δ into a heavy hole band Δ5(hh) and a light hole band Δ5(lh) is clearly resolved. The amount of the splitting is found to be < 200 meV. In addition, we find transitions from the spin-orbit split valence band Γ7. The valence band spin-orbit splitting at the Γ-point is determined to be (750 ± 50) meV. The dispersion behaviour of light and heavy hole bands and the spin-orbit split valence band as well as the resulting data for spin-orbit and light-hole/heavy-hole-band splitting of the topmost valence bands are compared to band structures calculated by nonlocal pseudopotential and self-consistent local-density approximations.

Carrier generation and multiplication processes in ZnS:Mn are investigated by synchrotron radiation luminescence experiments. Within the interband region ( E g ≤ hv ≤ 11 eV), radiationless recombinations of photogenerated carriers at surface states control the luminescence yield η( hv ) of both self-activated centres and Mn 2+ in ZnS:Mn. We present the results of excitation spectroscopy in the UV range and a quantitative description of η( hv ). η( hv ) depends on the absorption constant, the surface layer and the diffusion length of free carriers. Within the multiplication range (13 ≤ hv ≤ 30 eV) η( hv ) raises in good approximation to a parabolic band structure with the square of photon energy up to 25 eV. In addition a superposition of steps at well-defined energies is observed. This step-like increasing of the yield is explained by the specific band structure of ZnS.

The decay of the integral band-to-band photoluminescence (PL) at (100) orientated n-doped GaAs (Te; n0 = 5×1017 … 1×1018cm3) in contact with aqueous 1 M HCl was investigated with the time-correlated single photon counting technique. The PL-decay was measured at various externally applied potentials, at constant and low density of injected carriers (pi≪n0), and at an excitation wavelength of λexc = 647.1 nm. The studies included electrodes modified by dipping in a solution of 5×10−3 M RuCl3 in 1 M HCl for 20 minutes. It was observed that the PL-decay measured at low injection level shows a reproducible and characteristic dependence on the externally applied potential. Within the accuracy of our time-correlated single photon counting equipment, the PL-decay time remains nearly constant and short in the range of potential U = (−0.3 … −0.9) V(Ag/AgCl). For the nonmodified electrodes the PL-decay time increases with increasing cathodic polarization in the range of potential U = (-0.9 … −1.1) V(Ag/AgCl) up to a maximum at U ≈ −1.1 V(Ag/AgCl), which corresponds to the (Mott-Schottky) flatband potential in the dark. At further cathodic polarization the cathodic current (due to the evolution of hydrogen) during the measurements becomes significant and it was observed that the PL-decay time decreases. After a treatment with Ru3+, the behaviour in the range of potential on the cathodic side of U = −0.9 V(Ag/AgCl) is different. The experimental observations could be confirmed qualitatively by results of computer simulations based on the Two-dimensional Semi-Conductor Analysis Package (TOSCA). At potentials on the anodic side of the flatband potential (depletion range) the decay times are short as well as independent of the degree of the band bending, of the surface recombination velocity, and of the photocurrent, respectively. This observation will be interpreted qualitatively by including the diffusion of the minority carriers toward the (dark) depletion layer as a competitive process for the radiative recombination in the bulk. Near the flatband potential the decay time of PL increases within a potential range of ΔU ≈ 200 mV depending on the density of injected carriers as well as on the rates of the surface recombination and of the minority carrier transfer (photocurrent). Based on a qualitative explanation for this characteristic dependence of the PL-decay time on the potential, the values of the surface recombination velocity and of the exchange photocurrent density are estimated to be S0

High resolution reflectance spectroscopy experiments were performed to study the Zn 3d states of Zn 1- x Mn x S over the whole concentration range (0≤ x ≤0.56). For zincblende-type samples ( x 5 state due to spin-orbit interaction is Δ so =251 meV. For the core exciton binding energy, a value of 517 meV is determined. For wurtzite-type samples ( x >0.05), the core exciton derived structures are broadened, reflecting the tenfold splitting of the 3d states under C 6v symmetry.

We report on synchrotron radiation reflectance spectroscopy experiments on the interband transitions of Zn 1− x Mn x Se for concentrations 0 ≤ x ≤ 0.4 within the energy range from 2 to 15 eV at a temperature of 30 K. By use of Kramers-Kronig transformation, the dielectric function was calculated, the imaginary part of which was analysed. In addition to the well-known anomalous concentration dependence of the band gap, the same anomaly is found for the critical point transitions E 1 and E 1 + Δ 1 and for the Zn 3d core level transitions. For all other critical point transitions we find a linear concentration dependence. The anomalous behaviour is discussed by means of sp-d exchange interaction, assuming that this interaction influences mainly s-like conduction states but that the influence vanishes for mainly p-like conduction states.

Reflectance spectroscopy experiments have been carried out to investigate the behaviour of the fundamental transition of Zn1-xMnxTe as a function of Mn mole fraction x and temperature: Eg=f(x, T). For the first time a nonlinear composition dependence is reported. The overall composition dependence can be approximated by two linear functions for the concentration ranges 0 0.1, respectively. This bandgap anomaly can be explained within the framework of the exchange interaction. The temperature dependence for small amounts of manganese can be approximated satisfactorily by Varshni's formula, but for manganese concentrations x>0.1 an additional blue shift of Eg is observed.

The time-resolved decay of band-to-band photoluminescence for n-GaAs (n 0 =5×10 17 cm -3 and 1×10 18 cm -3 ) in contact with aqueous electrolyte was investigated both experimentally (by a sampling technique) and theoretically (by computer simulation) by varying the excitation intensity with an externally applied potential near the point of zero photocurrent under steady state illumination (-0.5 V (SCE)). The band-to-band luminescence decay was observed experimentally at an excitation wavelength of 636 nm in a range of excitation intensity between 1440 and 0.49 kW cm -2 corresponding to initial excess carrier densities p i between 5.5×10 19 and 2×10 16 cm -3

We present the first experimental data obtained from the new microfocus beamline U41-PGM recently put into operation. The optical layout of the beamline has been designed to conserve the high spectral brillance of the undulator source. The beamline consists of a collimated plane grating monochromator (PGM) and a subsequent refocusing stage. A toroidal mirror is used for refocusing onto the sample surface. With the 600 1/mm grating an absolute photon flux between 10 12 and 10 13 photons per second has been recorded over the whole energy range. Although the monochromator is not designed to deliver highest energy resolution, a resolving power of up to 6000 at the nitrogen K-edge has been obtained recently. The fixfocus constant c ff is variable in a wide range. According to the experimental requirements it can be set to select either high photon flux or energy resolution.

The electronic structures of free and hydrogen covered As-terminated GaAs(100) surfaces were calculated using a selfconsistent local-density functional LCAO-method with a minimal basis set of optimized atomic orbitals. Comparison with experimental and other theoretical results for the bulk electronic structure prove the realiability of this non-empirical method for electronic states in the valence band region. Surface calculations using the slab model with 1 × 1 geometry give hydrogen-induced and GaAs surface states within those energy regions where they have been found with angle-resolved photoemission.

Results of local density first principles LCAO calculations for a 13 layer slab of free and modified As-terminated (1 × 1) GaAs(001) surfaces are presented. The surfaces are covered by a monolayer of hydrogen, copper, or ruthenium. The surface calculation for the hydrogen covered surface gives hydrogen-induced and GaAs surface states in agreement with angle-resolved photoemission results within the energy range where they are found. For the systems GaAs(001):Cu and GaAs(001): Ru metal induced gap states are predicted with a density of 2 × 1015 cm−2. The calculated surface states indicate a higher Schottky barrier for the ruthenium than for the copper covered surface. Ergebnisse nichtempirischer LCAO-Berechnungen auf lokaler Dichtenaherung fur die Elektronenstruktur freier und modifizierter (1 × 1) GaAs(001)-Oberflachen werden vorgestellt. Die Oberflachen werden durch 13 Atomlagen dicke Slabs modelliert und sind mit einer kompletten Monolage Wasserstoff, Kupfer bzw. Ruthenium bedeckt. Fur die mit Wasserstoff bedeckte GaAs(001)-Oberflache stimmen die Ergebnisse gut mit experimentellen, aus winkelaufgeloster Photoemission stammenden Befunden uberein. Fur die Systeme GaAs(001): Cu und GaAs(001): Ru werden durch das Metall induzierte Gap-Zustande mit einer integrierten Zustandsdichte von 2 × 1015 cm−2 erhalten. Die energetische Lage der berechneten Oberflachenzustande erklaren die hohere Schottkybarriere der Ru-bedeckten Oberflache gegenuber der Cu-bedeckten.

The subbandgap photocurrent dependence on electrode potential and light energy has been investigated for the n-GaAs(100) | 1 M HCl junction after surface modification by electroless deposition of ruthenium. A pronounced peak in the photocurrent-potential curve was found for Ru-treated electrodes between −0.6 and −0.1 V/SCE. This behaviour is explained in a model simulation for the photocurrent which takes into account the hole generation in a Ru-induced surface state by absorption of subbandgap light.

High resolution reflectance spectroscopy experiments were performed on Zn 1- x Mn x S , Zn 1- x Mn x Te and Cd 1- x Mn x Te within the energy range of cation d-level transitions. By use of a Kramers-Kronig transformation the dielectric function is calculated, the imaginary part of which is being analyzed. For the zinc-based SMSCs core level excitons are observed, having a binding energy of 332 ± 47 meV for Zn 1- x Mn x Te and 519 ±17 meV for zincblende-type Zn 1- x Mn x S , respectively. For wurtzite-type Zn 1- x Mn x S the binding energy is 793±78 meV. From the core level excitons the spin-orbit splitting of the cation d-levels is derived. For pure ZnS having zincblende structure it is determined to be (262±8) meV. In the wurtzite-type modification for manganese concentrations above x = 0.05, the splitting increases to (387±56) meV due to the change in crystal structure.

Resonant photoemission spectroscopy (RPES) is used as a probe for manganese derived features in photo-electron energy distribution curves (EDCs) of semimagnetic semiconducting (SMSC) thin films of ZnMnS. Photoemission spectra, taken in the range of the Mn 3p-3d and 2p-3d thresholds, show a resonant enhancement at 3.3 eV binding energy (BE), which represents a localized Mn 3d contribution. Its dependence on photon energy reveals a Fano line shape. The partial density of Mn states in ZnMnS is compared to results obtained for CdMnTe and ZnMnSe. Additional information on the initial state configuration of Mn is delivered by RPES in the range of 2p-3d transitions.

Linear, weakly nonlinear, and strongly nonlinear pattern forming properties of binary fluid convection and of systems with throughflow are elucidated with a broad spectrum of numerical and analytical methods and reviewed in comparison with experimental and other theoretical work. Growth dynamics, spatiotemporal behavior, stability, scaling properties, and bifurcation behavior of spatially extended stationary, traveling wave, and standing wave convective roll structures are presented. Also pulselike spatially localized traveling wave convection is investigated. The Dufour effect in gas mixtures is reviewed. 3D square and crossroll patterns and oscillations between them which occur in liquid mixtures are analyzed. In the second part the influence of an externally imposed shear flow on structure formation is investigated. The unique selection of a self sustained forwards bifurcating pattern in the absolutely unstable parameter regime is shown to be a nonlinear eigenvalue problem. Noise sustained pattern growth in the convectively unstable regime is analyzed as a result of bulk thermal fluctuations and of perturbations that are swept by the throughflow into the system via the inlet. Finally, the influence of a lateral flow on linear and nonlinear properties of binary mixture convection is studied with special emphasis on the symmetry breaking of Hopf degenerate traveling waves and their sub critical bifurcation topology.

The system CuGaSe2–CuGa3Se5 in thin films has been investigated. Layer synthesis was carried out by chemical close-spaced vapour transport (CCSVT) using Cu precursors on Mo/soda-lime glass substrates. The extension of deposition times in a two-step process led to final film compositions with [Ga]/[Cu] ratios ranging from 1 to 3, allowing the study of the phase transition mentioned above. Films showing chalcopyrite (1:1:2), OVC (1:3:5) and both phases were grown. X-ray emission spectroscopy and X-ray diffraction (XRD) techniques have been combined for a compositional and structural study of this material system probing both bulk and near surface properties of the films. This analysis was also extended to the rear-surface investigation of selected two-phase thin films and complemented with surface sensitive photoelectron spectroscopy (PES). From these results a growth model is presented for CuGa3Se5 formation in gallium rich, CCSVT-grown CuGaxSey-films.

Polar (100) surfaces of commercial CdTe and Cd(Zn)Te single crystals were prepared by ion sputtering and annealing at different temperatures and under Te flux, Cd flux, or in ultrahigh vacuum. Various surface reconstructions with high structural order were obtained. Soft x-ray photoemission investigations of the Cd and Te 3d surface core-level shifts were employed to derive the surface termination, revealing Cd-terminated surfaces for most preparations and various reconstructions. The results suggest that sputter/annealing cycles are suitable for the preparation of highly ordered and uniformly terminated substrates for semiconductor heterojunctions on CdTe and Cd(Zn)Te without the need of an additional buffer layer.

For chalcopyrite-based solar cells with conventional CdS buffers (prepared in a chemical bath), the Cd/sup 2+//NH/sub 3/-treatment can be used as a tool to visualize the processes during the initial stages of interface formation in the chemical bath. For high-gap CuGaSe/sub 2/ (CGSe) - an absorber material which has not yet shown its full potential in terms of solar cell performance - a CdSe surface compound was recently identified at the CGSe absorber surface after this kind of simple surface conditioning. In this contribution, we will clarify whether the [Ga]/[Cu]-ratio of the CGSe absorber has an impact on the formation of this non-abrupt interface. In addition, the lateral variation of the observed absorber surface modification will be investigated. Thus, as-deposited and Cd/sup 2+//NH/sub 3/-treated CGSe surfaces were characterized by X-ray excited Auger and photoelectron spectroscopy using Mg K/spl alpha/ and/or tuneable monochromatized synchrotron radiation.

Zinc-based buffer layers like ZnSe, ZnS, or wet-chemically deposited ZnO on Cu(In, Ga)(S, Se)2 absorber materials (CIGSSe) have yielded thin film solar cell efficiencies comparable to or even higher than standard CdS/CIGSSe cells. However, little is known about surface and interface properties of these novel buffer layers. In this contribution we characterize the specific chemical environment at the absorber/buffer-interface using X-ray Emission Spectroscopy (XES) and Photoelectron Spectroscopy (PES) in a complementary way. Evidence of intermixing and chemical reactions is found for different buffer materials and deposition methods.

A systematic analysis of the embedded atom EXAFS (AXAFS) effect is presented. This effect is explained by the backscattering of the photoelectron at interstitial charge densities. The reconstructed (2 × 1)O/Cu(110) system is an ideal prototype system in which to study the angular dependence of the AXAFS because oxygen–copper rows are formed resulting in a C2 symmetry. The scattering potential is non-spherical because of the high directionality of the O–Cu bonds. The high signal-to-noise ratio of the experimental data enables us to clearly identify the AXAFS contribution. Here we present the definite angular dependence of the experimental AXAFS for the first time, giving a unique opportunity to measure the anisotropy of the local embedded atom potential. The angular dependence demonstrates that the AXAFS effect cannot be mimicked by multi-electron excitations or experimental artifacts for this system. We compare our experiments to theoretical calculations within the muffin-tin approximation and show that future full-potential calculations are needed to model the angular dependence determined.

Investigating LaNi(1-x)M(x)O3 (M = Mn and Fe), we identify a characteristic evolution of the spectral function with increasing disorder in presence of strong interaction effects across the metal-insulator transition. We discuss these results vis-a-vis existing theories of electronic structure in simultaneous presence of disorder and interaction., Revtex, 4 pages, 3 postscript figures (To appear in Phys. Rev. Lett)

From x-ray absorption spectroscopy at the C K edge we show that interface effects in C60-Al multilayers give rise to a predominantly covalent interaction between the fullerene molecules and the metal, with minimal ionic charge transfer. In addition, an anomalous q-dependence of the spectral weight of the Al charge carrier plasmon is observed in electron energy-loss measurements, which could be related to the confinement of the Al layers between the fullerene dielectric.

Film formation of decanethiol [CH3(CH2)9SH], didecyl disulfide [CH3(CH2)9S−S(CH2)9CH3], and didecyl sulfide [CH3(CH2)9−S−(CH2)9CH3] on polycrystalline gold from ethanol solutions was studied in situ by second harmonic generation. The completed films were characterized by X-ray photoelectron spectroscopy and voltammetry. Film formation is described by Langmuir adsorption kinetics and is found to be fastest for the thiol. Referenced to the number of thiolate units the disulfide adsorbs about 40% more slowly. In sharp contrast, the rate of alkyl sulfide adsorption is smaller by more than 3 orders of magnitude. Films formed from the thiol and disulfide are indistinguishable and virtually free of contaminations. In contrast, the maximum coverage achieved with the sulfide is considerably lower and substantial amounts of contamination remain on the substrate. Differences between thiol/disulfide films and sulfide films are also indicated by their electrochemical behavior.