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Thermal and cold neutrons are a perfect tool to investigate massive and large (several cm3) samples by means of computerized tomography (CT). The main interaction to visualize structures in samples is absorption, similar to x-rays in medicine or material research. Based on absorption new techniques such as energy dependent CT or real time CT have gained importance within the last years and were used to show e.g. the movement of pistons in engines. Absorption, however, is not the only interaction that can be used for computerized tomography. Other interactions such as interference effects, so-called phase based interactions, were exploited for CT to visualize details in samples that could not be detected by absorption. Phase contrast imaging was first applied to x-ray CT, but soon it was also applied to neutron CT. Based on the same interaction, refraction and ultra small angle scattering of neutrons were studied and successfully applied to neutron tomographic investigations of samples. These new imaging signals (refraction and ultra small angle scattering) require entirely different techniques, different experimental set ups (high resolution double crystal diffractometer) and special data evaluation, to detect these signals and separate them from absorption and noise. Using absorption and phase-based signals the length scale of tomography with neutrons is more than five orders of magnitude, which covers a large field of non-destructive testing in material research and fundamental physics. [ABSTRACT FROM AUTHOR]

Similar to the imaging with X-ray, neutron imaging systems have been shifted more and more from film exposure towards direct digital detection in the last decade. This approach enables the option for tomography because the image content is measured and understood as dataset now. With the help of mathematical algorithms it becomes possible to derive the necessary information about the full three-dimensional volume of an object from a set of projections from different viewing angles. Neutron tomography (NT) with best performance requires a strong and well collimated neutron beam. Such beam lines for either thermal or cold neutrons are available at reactor based sources (FRM-2, HMI, ILL) or at spallation neutron sources (PSI). The beam geometry for neutrons is in the best case a parallel one, delivering a sharp 1:1 transmission image of the object under investigation. Therefore, the limited detector resolution is responsible for the tomography resolution generally. In practical reality, objects with outer dimensions up to 40 cm can be inspected with a nominal resolution of up to 0.1 mm. This compares well with similar X-ray tomography systems used in non-destructive testing (NDT) tasks. However, the application fields in neutron tomography are different, given by the different interaction probability with matter. Neutrons have the advantage to penetrate most metals (especially heavy ones) very efficiently and to detect hydrogenous compounds very sensitively. Therefore, neutron tomography has application fields in moisture detection, test of adhesive connections, structure analysis for soil and geologic samples and the non-invasive investigation of objects from our cultural heritage. Based on some practical applications, the paper describes the present state of the art of this technique and gives a prospect for further improvement. [ABSTRACT FROM AUTHOR]

For semiconductor industry, the challenges to future process technology and advanced materials are outlined in the International Technology Roadmap for Semiconductors (ITRS) [1]. Microelectronic and further nanoelectronic products of the next technology generations will need advanced materials particularly for device structures since the traditional shrinking of feature sizes is reaching fundamental physical limits. Currently, leading-edge microprocessor (MPU) technology is pushing material innovations in the gate stack of metal-oxide-semiconductor field effect transistors (MOSFETs). [ABSTRACT FROM AUTHOR]

AlGaN/GaN electrolyte gate field-effect transistors are assessed as a transducer device for biosensor applications. Their low-frequency noise power spectral density exhibits a 1/f characteristic with a dimensionless Hooge-parameter of 5×10-3. The equivalent gate-input noise under operation conditions has a peak-to-peak amplitude of 15 μ V, one order of magnitude smaller than for common silicon-based devices. The untreated GaN device surface showed a high linear pH response of 56 - 57 mV/pH, whereas the sensitivity to other ions is comparably low. Arrays of these transistors have been used for monitoring of action potentials from a confluent layer of rat heart muscle cells cultivated directly on the non-metallized gate surfaces and signals with an amplitude of 1.2 mV were recorded. [ABSTRACT FROM AUTHOR]

The aim of the present paper is to study the influence of the particle size on the properties of BaTiO3 and PbTiO3 materials by means of a NMR and EPR spectroscopy. Mn2+ EPR and 137Ba NMR measurements were performed on BaTiO3 particles with average diameters between 15 nm and 255 nm. Cr3+ EPR spectra were measured on PbTiO3 fine powders with mean particle diameters ranging from 6 nm to 210 nm. Typical changes in the fine structure and the quadrupole coupling tensors are observed in the ferroelectric tetragonal phase which allow information about the structure model for the nanoparticles and the critical particle size. [ABSTRACT FROM AUTHOR]

We discuss the atomic and electronic structures and energetics of native point defects and of impurities (Si, Ti, B, moisture) in PrO1.5 and, to some extent, also in PrOx and in PrSiO3.5, as obtained from ab initio total energy calculations. We introduce the concept of Silicon-related Nitrogen-Coordinated Oxygen (SiNCO) which we then use to explain the origin of fixed charge in classical SiO2 films thermally grown on Si substrates and in high-k dielectrics deposited on Si substrates. [ABSTRACT FROM AUTHOR]

Ion beams provide unique opportunities for modifying thin film structural and mechanical properties on length scales ranging from several nanometers to macroscopic dimensions. In a variety of materials, including polycrystalline and amorphous metals and semiconductors, plastic effects can dominate, which originates from processes in the small volumes of materials affected by a single ion impact. The underlying atomic-scale kinetics as well as its applications for self-organized structuring are investigated using a combination of experiments and molecular-dynamics (MD) computer simulations: We report experiments, that illustrate the impact of radiation induced viscous flow on morphology and stresses, such as interface smoothing, stress relaxation, radiation induced sintering or self-organized pattern formation. Using MD simulations we study the underlying atomic-scale mechanisms for the two energy regimes, where local melting along the ion track is either dominant or not. We show, that macroscopic plastic flow does not require melting, indicating, that defect-like entities are sufficient to mediate plastic flow. [ABSTRACT FROM AUTHOR]

Metal contacts to organic semiconductors play a decisive role for the performance of organic based devices such as organic light emitting diodes, organic field effect transistors or organic solar cells. In particular when a metal is deposited onto an organic substrate, severe disruption of the interface may occur as a result of chemical reactions of the metal with organic molecules and/or diffusion of the metal into the organic layer. Here, the interaction of metals of different reactivity (Ag, In, Mg) with a variety of perylene derivatives as model molecules is probed employing in situ Raman spectroscopy. The results reveal that this technique allows an extreme interface sensitivity to be achieved via surface enhanced Raman scattering. The degree of reactivity and indiffusion can be derived from the analysis of the evolution in scattering by internal vibrational modes of the molecules and phonon-like external modes of the molecular crystal. [ABSTRACT FROM AUTHOR]

Surface as well as interface properties are crucial for tailoring advanced materials, especially if the structure size in one or more dimensions approaches the nanoscale regime. Thus, analysis and modification of the last atomic layer is of crucial importance. Optical probes for analysis offer the advantage of high spectral resolution and the possibility to analyze under liquid, vapor and vacuum environments. With emphasis on Raman spectroscopy various examples of analysis of structural and binding properties of such monolayers are presented. Especially materials used in electronic applications are addressed. Examples are determination of the surface reconstructions of II-VI semiconductors and overgrowth analysis by Raman spectroscopy and the modification of bonding properties of organic molecules, i.e. 3,4,9,10-perylene-tetracarboxylic-dianhydride (PTCDA), at metallic surfaces. [ABSTRACT FROM AUTHOR]

In the first chapters we give some short comments on the history of ZnO research and on growth, doping, transport, and deep centers, topics which will be covered in more detail by other contributions to this symposium "ZnO-rediscovered". Then we concentrate in a first main chapter on the band-structure, excitons, and polaritons in the regime of linear optics. The second main chapter deals with many particle effects and lasing. It is followed by a short conclusion and outlook. [ABSTRACT FROM AUTHOR]

Diffusion experiments of N, Li, and Na into single-crystal substrates of ZnO were performed. The diffused layers were studied using mass spectroscopy and low temperature photoluminescence. Based on earlier investigations Li and Na produce deep acceptor states which participate in shallow donor to deep acceptor recombinations in the visible spectral region. We will demonstrate that in the case of group-I elements also shallow acceptors are introduced having binding energies around 300 meV. The corresponding donor-acceptor pair recombinations have weak electron-phonon coupling analogous to the "edge" emissions in other II-VI compounds. With 160 meV nitrogen so far has the smallest ionisation energy. We compare our results with ZnO epitaxial films where the respective elements are incorporated during growth. [ABSTRACT FROM AUTHOR]

We have investigated and compared the electrical properties of ZnO grown by four different methods. From temperature dependent resistivity and Hall measurements the parameters of the dominant donors are obtained. Deep level transient and thermal admittance spectroscopy have been applied to study deep states in ZnO. The energetic position of deep donors has been identified for ZnO thin films for the first time. We have found the levels E1 (Ed = 110 meV) and E3 (Ed = 290 meV). Semi-insulating ZnO thin films grown by PLD have been demonstrated by three methods: avoiding the incorporation of shallow donors, compensation with acceptors, and co-doping. Further we report a Schottky diode structure enabling the use of ohmic back contacts for ZnO grown on insulating substrates with cut-off frequencies > 10 MHz. Schottky contacts on ZnO thin films are characterized by current voltage measurements for temperatures ranging from 210 K to 293 K and the results are evaluated considering the lateral fluctuations of the barrier height. The Schottky barrier height of Pd/ZnO has been determined to be 1.1 eV with a standard deviation of the lateral fluctuations of 130 meV. [ABSTRACT FROM AUTHOR]

We review recent progress in the understanding of electron spin relaxation mechanisms in zinc-blende semiconductors. Increased spin lifetimes are obtained in structures with special orientation of crystal axes making them suitable for room temperature spintronic devices. In such structures the electron spin lifetime is found to critically depend on spin orientation, which directly affects the design rules for spin devices. We present new calculations concerning the recently introduced intersubband spin relaxation (ISR) mechanism. The mechanism becomes effective at elevated temperatures as scattering between higher electronic subbands starts to occur. [ABSTRACT FROM AUTHOR]

It is by now generally accepted that the recently discovered superconductor MgB2 is a superconductor with two energy gaps. Here we discuss how this happens and address some of its unusual implications. The anisotropy ratio of the upper critical field in MgB2 single crystals shows an unusual strong temperature dependence. Measurements of the microwave conductivity on MgB2 thin films have shown an anomalous coherence peak appearing at significantly lower temperatures than in conventional superconductors. We argue that both of these observations are natural consequences of the existence of the two gaps, if the special Fermi surface structure of MgB2 is taken into account. We also examine consequences for the expected intrinsic nonlinear microwave response in MgB2. Calculations including impurity scattering indicate that under certain circumstances impurity scattering might improve the microwave properties of this material. [ABSTRACT FROM AUTHOR]

Results of light-scattering experiments in Bi2Sr2CaCu2O8+δ (Bi-2212), La2-xSrxCuO4 (LSCO), and YBa2Cu3O6+x (Y-123) single crystals are presented. The emphasis is placed on the low doping range where the evolution of the metallic state from the antiferromagnetic one is studied. Along the diagonals of the CuO2 planes the response is metallic even at small doping levels well below p = 0.05 where superconductivity disappears. In contrast, along the principal axes the carriers exhibit insulator-like characteristics up to approximately p=0.21. In the underdoped range charge-ordering fluctuations are observed manifesting themselves as quasielastic peaks at low temperatures. The symmetries at which the new response is found are compatible with the neutron results on the spin system. Possible connections between the localization phenomena, the pseudogap and the charge and spin-ordering instabilities as well as the implications for superconductivity are discussed. [ABSTRACT FROM AUTHOR]

In the past decades it has become evident that a growing number of metals exhibit exotic types of superconductivity as manifested by their thermodynamic and transport properties. Multi-band superconductivity has attracted renewed interest triggered by experimental results on MgB2 and Nb3Sn. Unconventional superconductivity is observed in many U- and Ce-based heavy-fermion superconductors as well as in the oxide superconductors. Among other methods, point-contact spectroscopy is an important tool to study the symmetry and the nodal structure of the energy gap Δ. Andreev reflection of charge carriers at the normal metal/superconductor interface leads to minima at V≈ ± Δ /e in the differential resistance dV/dI as a function of applied bias V and thus allows determination of the gap size. In addition, Andreev reflection causes an excess current through metallic (low-barrier) point contacts and the temperature dependence of the excess current can be analyzed with respect to the order-parameter symmetry. Here, recent developments in this field will be reviewed with a particular focus on investigations of the heavy-fermion superconductor CeCoIn5, a possible d-wave superconductor, and the oxide superconductor Sr2RuO4, a candidate for p-wave superconductivity. [ABSTRACT FROM AUTHOR]

A brief review is given on a spin Hall effect, where an external electric field induces a transverse spin current. It has been recognized over 30 years that such effect occurs due to impurities in the presence of spin-orbit coupling. Meanwhile, it was proposed recently that there is also an intrinsic contribution for this effect. We explain the mechanism for this intrinsic spin Hall effect. We also discuss recent experimental observations of the spin Hall effect. [ABSTRACT FROM AUTHOR]

The analysis of network models - either directly or by numerical studies of related quantum spin chains with super group symmetry - allows to gain insights into the delocalization transition of non-interacting two-dimensional electrons with disorder. Critical exponents determined this way are an important step towards the identification of the conformal field theory (CFT) describing the universal physics at the transition. To collect more information on the universal properties integrable versions of the corresponding superspin chains have been proposed. A simplified version avoiding some of the technical problems of the original problem is the sl(21) superspin chain related to the so-called spin quantum Hall transition. Analyzing the ground state and some low-lying excitations of this integrable chain we determine the central charge of the underlying CFT and obtain evidence for an infinite degeneracy of the finite size gaps that are possibly related to a continuous spectrum of the CFT. Finally, we compare our findings for the integrable chain with known properties of the (non-integrable) network model for the spin QHE. [ABSTRACT FROM AUTHOR]

In a single self-assembled InGaAs quantum dot, the one exciton ground state transition defines a two-level system, which appears as an extremely narrow resonance of only a few μeV width. The resonant interaction of this two-level system with cw laser fields can be studied in detail by photocurrent spectroscopy, revealing the fine structure of the excitonic ground state as well as the effects of nonlinear absorption and power broadening. For the case of pulsed laser fields and in the absence of decoherence, the two-level system represents a qubit. Excitations with ps laser pulses result in qubit rotations, which appear as Rabi oscillations in photocurrent experiments. Double pulse experiments further allow us to infer the decoherence time and to perform coherent control on a two-level system. [ABSTRACT FROM AUTHOR]

The theory of surface optical properties is reviewed. The use of Many-Body Perturbation Theory, with Density Functional Theory calculations as zero order approximation, is now the state of the art to obtain quasi-particle excitation energies and optical spectra of surfaces. In this paper we will present the current status of theoretical and computational approach. Realistic calculations of surface optical properties within the single-particle approximation and within the Many-Body Perturbation Theory are discussed; as examples, results for InAs(110) and C(100) surfaces are given. [ABSTRACT FROM AUTHOR]

A prerequisite for an efficient "molding the flow of light" by photonic crystals is the molding of materials in desired nanostructures. Very often, conventional materials and processing techniques cannot fulfill the theoretical requirements for the materials and structures. Sol-gel methods enable material processing in opal pores and the controlled introduction of sub-wavelength pores into the materials by the use of molecular or supramolecular templates. The porosity can be used for lowering the refractive index, for soft processing of the materials and for stress relaxation. Examples for this approach are ultra-low refractive index films used as support for 2D photonic crystals, inverse opals with a skeleton-like unit cell filling and ferroelectric films with high transparency. In detail, we describe mesoporous silica films with a refractive index of 1.14 for use in 2D photonic crystal waveguide systems and the structure tuning possibilities of inverse opals. [ABSTRACT FROM AUTHOR]

The self-energy-functional approach (SFA) is discussed in the context of different variational principles for strongly correlated electron systems. Formal analogies between static and dynamical variational approaches, different types of approximation strategies and the relations to density-functional and dynamical mean-field theory are emphasized. The discussion elucidates the strengths of the SFA in the construction of new non-perturbative approximations but also the limitations of the approach and thereby opens up future perspectives. [ABSTRACT FROM AUTHOR]

Full counting statistics aims at a complete characterization of the distribution of measurement outcomes. In this article I will demonstrate how this concept allows to investigate quantum correlations in a variety of mesoscopic systems. Three examples will be discussed: a) In analogy to Schottky's work on the current fluctuations in a vacuum diode, shot noise in superconducting contacts allows to identify the nature of the elementary charge transfer events. b) The Coulomb interaction in complex quantum dots or molecules leads to a strongly correlated current statistics. c) The density fluctuation statistics in a fermionic quantum gas reflects the crossover from a superfluid state to a molecular Bose-Einstein condensate. [ABSTRACT FROM AUTHOR]

Cold atoms in optical lattices offer an exciting new laboratory where quantum many-body phenomena can be realized in a highly controlled way. They can serve as quantum simulators for notoriously difficult problems like high-temperature superconductivity. This review is focused on recent developments and new results in multi-component systems. Fermionic atoms with SU(N) symmetry have exotic superfluid and flavor-ordered ground states. We discuss symmetry breaking, collective modes and detection issues. Bosonic multi-flavor ensembles allow for engineering of spin Hamiltonians which are interesting from a quantum computation point of view. Finally, we will address the competition of disorder and interaction in optical lattices. We present a complete phase diagram obtained within dynamical mean-field theory and discuss experimental observability of the Mott and Anderson phases. [ABSTRACT FROM AUTHOR]

Recent research on the non-stationary nature of the dynamics of complex systems is reviewed through three specific models. The long time dynamics consists of a slow, decelerating but spasmodic release of generalized intrinsic strain. These events are denoted quakes. Between the quakes weak fluctuations occur but no essential change in properties are induced. The accumulated effect of the quakes, however, is to induce a direct change in the probability density functions characterizing the system. We discuss how the log-Poisson statistics of record dynamics may be an effective description of the long time evolution and describe how an analysis of the times at which the quakes occur enables one to check the applicability of record dynamics. [ABSTRACT FROM AUTHOR]

An overview on a new operational method is given which disentangles deterministic dynamical evolution laws from the impact of fluctuating forces for nonlinear Langevin equations. An important extension is also reported. The extension overcomes possible problems which may arise for data sets sampled at low frequencies, and data sets which do not contain sufficient amount of data. [ABSTRACT FROM AUTHOR]

Fluid lipid membranes, which, together with filamentous proteins like actin, form the basic structural component of cells, have been a central topic of biological physics for the last twenty years. Traditionally, soft matter research has mainly focused on equilibrium or near equilibrium properties. In this respect, we review our work on the dynamics of simple model membranes, which are mechanically or chemically perturbed. We consider both lipid as well as diblock-copolymer membranes. Future opportunities for physics are opening up in the study of active biological systems using a modular approach. We summarize our recent work on the spreading dynamics of mouse embryonic fibroblast cells on adhesive substrates. In a somewhat reductionistic approach such an advancing cell can be considered to consist of a few main modules. An active motile gel wrapped by a membrane relaying environmental information is coupled to the cellular signaling network and the reproductive machinery. We monitored the dynamics of the leading membrane edge reflecting dynamic phase transitions of the enclosed active gel. We argue that observing cellular modules and phases will provide a powerful tool for quantitative cell biology. Physics must formulate new general concepts for interacting active modules and protein networks. [ABSTRACT FROM AUTHOR]

We discuss molecular diffusion in nanopores with different types of roughness under the exclusion of mutual molecular collisions, i.e., in the so-called Knudsen regime, both, in d=2 and d=3. We show that the diffusion problem can be mapped onto Levy walks and discuss the roughness dependence of the diffusion coefficients Ds and Dt of self- and transport diffusion, respectively. We find that in d=2, the diffusion is anomalous with Ds~ln t and Dt~ln L, whereas in d=3, the logarithmic corrections are absent. Both diffusion coefficients decrease significantly when the roughness is enhanced, in remarkable disagreement with earlier findings. [ABSTRACT FROM AUTHOR]

Amongst biomolecules the DNA base molecules adenine, cytosine, guanine, and thymine may also find interesting applications in organic electronics. They have optical gaps in the near ultra-violet and have already been considered as charge transport molecules in organic field effect transistors. Still there is very little knowledge on their electronic and optical properties when deposited as layers on inorganic substrates. Here the optical properties of the DNA bases deposited on flat and vicinal, hydrogen passivated Si(111) substrates are studied using spectroscopic ellipsometry (SE) up to 9.5 eV photon energy employing synchrotron radiation and reflectance anisotropy spectroscopy (RAS). The results for the dielectric function reveal strong optical anisotropy for adenine and guanine while the other two molecules form layers with isotropic properties. The experimentally derived dielectric functions are compared to density functional theory calculations of the optical response. Particularly interesting is the RAS response of the DNA bases as a function of thickness when deposited on vicinal Si surfaces. Ordering in the layers is induced by the step and terrace structure of the vicinal Si substrates. Even though the molecular structure is not dramatically different the RAS response is very distinct and allows an unambiguous identification of the bases. [ABSTRACT FROM AUTHOR]

Recently we have shown how to tune length- and timescales in demixed colloid-polymer dispersions in such a way that thermal capillary waves at the free interface between demixed fluid phases can be studied directly by means of laser scanning confocal microscopy [Aarts, Schmidt and Lekkerkerker, Science 304, 847 (2004)]. Here, we focus on several static properties of the interface. We show that the probability of fluctuations of the local interface position around its equilibrium value is Gaussian. By comparing two-point correlations of these fluctuations as a function of distance with predictions from capillary wave theory, we obtain results for the interfacial tension and the capillary length. The presented technique enables us to measure also the probability distribution of the tilt angle of the local interface normal and the vertical direction. [ABSTRACT FROM AUTHOR]

The diffusion of polymers within heterogeneous media is strongly dependent on the structure of the medium. We review neutron reflectometry and ion beam analysis measurements on (crosslinked) polystyrene films. In particular we consider the diffusion of polymers into and within polymer networks, and consider experiments to determine information on the structure of networks by swelling in their own homopolymer. Finally, we discuss the interpenetration of networks by linear polymer and polymer brushes. [ABSTRACT FROM AUTHOR]

We begin with historical remarks on the basic contributions to thermodynamics and statistics with some bias to scientists working in Berlin as Helmholtz, Clausius, Nernst and Einstein. We underline the key role of thermodynamic ideas in the scientific revolutions in the 20th century. Further we discuss several recent applications to natural, evolutionary and informational systems, exotic applications as well as perspectives and open problems. [ABSTRACT FROM AUTHOR]

The present understanding of the physics of correlated electrons in quantum wires is summarized in terms of non-Fermi liquid collective excitations. The latter are determined within the Luttinger liquid model by using the bosonization technique. Charge and spin density modes are derived. Comparison with the data from resonant Raman scattering experiments indicates that interactions dominate the low-frequency collective excitations. The latter are determined within the Luttinger liquid model by using the bosonization technique. Charge and spin density modes are derived. Comparison with the data from resonant Raman scattering experiments indicates that interactions dominate the low-frequency collective modes in semiconductor quantum wires. Former "single particle excitations" in the resonant Raman spectra have been found to be due to higher-order spin modes that appear in both polarizations of incident and scattered light. The interplay in the non-linear DC-transport properties of a Luttinger liquid model with two impurities between interaction, spin, and backscattering by the impurities is discussed and compared with recent experiments. The results indicate that linear transport probes the global properties of the system, including the leads and the contacts. On the other hand, the non-linear differential conductance probes the local correlations near the electron island between the impurities. [ABSTRACT FROM AUTHOR]