Abstract: This work explores from a theoretical viewpoint the mechanical properties of the most important hydration product present in cementitious environments, the so called C-S-H (calcium-silicate-hydrate) gel. The dependence of the bulk (K), shear (G) and Young's (E) modulus for the C-S-H crystals respect to its composition and the length of its silicate chains is analysed by lattice dynamic simulations with parameterised two-body and three-body potentials. Our simulations reveal that the mechanical properties of C-S-H crystals show a strong dependence on their composition. Nevertheless our calculated numbers systematically overestimate the experimental values for C-S-H gels. Only when the finite length of the silicate chains is taken into account this discrepancy disappears.

Abstract: We report the successful growth of quaternary Cu2ZnSnSe4 (CZTSe) thin films by pulsed laser deposition (PLD) using Nd:YAG laser. It was found that CZTSe films atomic ratios were close to target atomic ratios with a slight metal excess and selenium deficiency. Quaternary CZTSe films grew and crystallized as a stannite-type structure even at room temperature. All CZTSe films showed a p-type electrical conductivity with a high absorption coefficient of 104–105 cm–1, a bandgap of 1.5 eV and a carrier concentration of the order of 1017–1018 cm–3. These results show that pulsed laser deposition could be employed as a particularly effective deposition method for the preparation of quaternary compounds thin films. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Abstract: We fabricated three types of white light emitting diodes (LEDs). The first is the white LED, which has a high general color rendering index (R 0 ) of 97 and CRI-No. 9 of 96. The CRI-No. 9 denotes the color reproduction in the red region. These values are higher than those of a tri-phosphor fluorescent lamp (R a = 85 and CRI-No. 9 = 8). The second is the high efficiency white LED fabricated from the small-size high efficiency blue LED chip. The output power (P 0 ), the external quantum efficiency (η ex ) and wall-plug efficiency (WPE) of the small-size blue LED were 35.0 mW, 63.3% and 56.3%, respectively, at a forward-bias current of 20 mA. The luminous flux (Φ), luminous efficiency (η L ) and WPE of the second white LED are 8.6 lm, 138 Im/W and 41.7%, respectively. The luminous efficiency is 1.5 times greater than that of a tri-phosphor fluorescent lamp (90 lm/W). The third is the high power white LED fabricated from the larger-size blue LED chip. Po, η ex and W.P.E. are 458 mW, 47.2% and 39.7%, respectively, at 350 mA. Φ, η L and WPE of the third white LED are 106 lm, 91.7 Im/W and 27.7% at 350 mA, respectively. Moreover, Φ of 247 lm and 402 lm at 1 A and 2 A are obtained, respectively. Φ at 2 A is equivalent to the total flux of a 30 W incandescent lamp.

Abstract: In this paper we present our recent results on the production of primary particles of detonation diamond from strongly bound agglomerates using beads milling and the newly developed BASD (bead assisted sonic disintegration) method in various media. Additionally, the surface functionalisation starting from hydroxyl groups is discussed. These groups can be introduced by reductive surface homogenisation using borane. Further functionalisation includes the grafting of silanes and amino acids.

Abstract: Magnesium borate activated by dysprosium (MgB4O7:Dy) is a low-Zeff, tissue-equivalent material that is commonly used for medical dosimetry of ionizing radiations such as gamma and X-rays using the thermoluminescence (TL) technique. Nanocrystals of the same material are produced and their TL characteristics are studied. It is found that the nanocrystalline MgB4O7:Dy with a dopant concentration of 1000 ppm is the most sensitive amongst varying dopant concentrations, with its sensitivity equal to 0.025 times that of the standard phosphor CaSO4:Dy. The glow curve has two peaks at 154 °C and 221 °C. The nanophosphor has very poor sensitivity for low doses up to 10 Gy but beyond this dose the phosphor exhibits a linear response up to 5000 Gy. On increasing the dose further the response first becomes supralinear and then sublinear, finally resulting into saturation. Considering also its low fading particularly under post-irradiation annealing and excellent reusability features, this nanophosphor may be used for high dose (10–5000 Gy) measurements of ionizing radiations. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Abstract: The radiation hardness of silicon charged particle sensors is compared with single crystal and polycrystalline diamond sensors, both experimentally and theoretically. It is shown that for Si- and C-sensors, the NIEL hypothesis, which states that the signal loss is proportion al to the Non-Ionizing Energy Loss, is a good approximation to the present data. At incident proton and neutron energies well above 0.1 GeV the radiation damage is dominated by the inelastic cross section, while at non-relativistic energies the elastic cross section prevails. The smaller inelastic nucleon-Carbon cross section and the light nuclear fragments imply that at high energies diamond is an order of magnitude more radiation hard than silicon, while at energies below 0.1 GeV the difference becomes significantly smaller.

Abstract: In this paper we investigate cobalt doped ZnO thin films prepared via different sol-gel methods. XRD shows only the diffraction peaks from wurtzite ZnO without secondary phase, as widely reported in literature, for the Co contents of our samples of 3 to 12%. Raman spectroscopy reveals the existence of anti-ferromagnetic cobalt oxides like CoO and Co 3 O 4 already in intermediately doped samples. Furthermore, the Raman shifts of the doped samples exhibit a shift to higher energy with increasing Co doping content. Unfortunately, Raman spectroscopy is not sensitive to metallic Co and, therefore, cannot be employed to explore the presence of Co clusters. However, we demonstrate that XRD is not a suitable method to rule out the existence of magnetic secondary phases in ZnO doped with transition metals.

Abstract: EIS, CV and XPS experiments were carried out to address the evolution of H-terminated BDD electrochemical properties under intensive use and air aging. A drastic drop of apparent electron transfer rate k' 0 was thus recorded using Fe(CN 6 ) 3-/4- as the redox mediator by identifying components of the Randles equivalent circuit. Excellent agreement was observed between theoretical and experimental curves. The feasibility of recovering and stabilizing high reactivity and reversible behaviour by applying a suitable electrochemical post treatment was then demonstrated. Such a treatment was developed empirically and seemed to significantly improve the electrode performances. On the basis of our results, we claim that the electrochemical evolutions observed are strongly linked to chemical termination modifications and partial inactivation of the electrode surface. Further research on the mechanisms that govern electron mediation at the diamond surface would be of high interest for better control of diamond electrode stability and reactivity towards their applications for bio-electronic devices.

Abstract: The present work investigates lithium insertion into highly ordered nanotubular layers of TiO 2 and its electrochromic effects. The nanotubes were formed by anodization of titanium in 1 M (H 3 PO 4 ) + 1 M (NaOH) + 0.5wt% HF electrolyte at 20 V. This leads to nanotubular layers with a thickness of 1 ± 0.1 μm, individual tube diameter of 100 ± 10 nm and a tube wall thickness of 10 ± 2 nm. The cathodic behavior of tubes in the "as formed" amorphous phase and annealed to anatase were studied in a solution of 1 M LiCl0 4 in acetonitrile. Cyclic voltammograms and potential step experiments combined with reflectance measurements show for anatase nanotubes a well defined uptake potential for Li + and a very strong and reversible electrochromic effect, while on the other investigated TiO 2 structures the effects were much less pronounced.

Abstract: The understanding of blistering mechanisms at the fundamental, atomic-scale level is still not complete, but large strides towards that goal have been made in the last decade. In this issue's Review Article [1] Bernard Terreault gives a comprehensive survey of this progress, discussing the current questions as well as outlining suggestions for future work. The related cover picture shows atomic force micrographs of a variety of surface morphologies obtained by hydrogen ion implantation into silicon followed by rapid thermal annealing. In this particular case, the ions were implanted through PMMA masks of decreasing width (from left to right, 6 μm, 1 μm, 600 nm and 150 nm) [2]. This is but one application of blistering, the most common being ion-cutting and layer transfer as used in the commercial production of silicon-on-insulator wafers. The author is Honorary retired Professor at the EMT (Energy, Materials, Telecom) Center of the Institut National de la Recherche Scientifique (Universite du Quebec). Another feature included in the current issue is the Editor's Choice contribution ‘Optical and micro-analytical study of a copper–conjugated polymer composite’ by Kaushik Mallik et al. [3], where the authors investigate a nanoscale fiber network for potential application in microelectronic systems.

Abstract: Synchrotron-radiation computed laminography (SRCL) is developed as a method for high-resolution three-dimensional (3D) imaging of regions of interest (ROIs) in all kinds of laterally extended devices. One of the application targets is the 3D X-ray inspection of microsystems. In comparison to computed tomography (CT), the method is based on the inclination of the tomographic axis with respect to the incident X-ray beam by a defined angle. With the microsystem aligned roughly perpendicular to the rotation axis, the integral X-ray transmission on the two-dimensional (2D) detector does not change exceedingly during the scan. In consequence, the integrity of laterally extended devices can be preserved, what distinguishes SRCL from CT where ROIs have to be destructively extracted (e.g. by cutting out a sample) before being imaged. The potential of the method for three-dimensional imaging of microsystem devices will be demonstrated by examples of flip-chip bonded and wire-bonded devices.

Abstract: In the upper part of block-cast multicrystalline silicon one often finds silicon carbide and silicon nitride precipitates and inclusions. These contaminants can cause severe ohmic shunts in solar cells and thus decrease the efficiency of the solar cells very strongly. It is well known that the silicon carbide precipitates cause the ohmic shunts. However, the electrical properties of the silicon carbide was unknown so far. To study the electrical properties of these silicon carbide particles we isolated them from the silicon bulk material and performed different electrical measurements on them. The measurements show that the silicon carbide precipitates are highly conductive. An investigation of the heterojunction silicon – silicon carbide was also performed and a simulation of this heterojunction leads to a new model of the ohmic shunt mechanism. It is concluded that the shunt current flows inside of the filaments.

Abstract: Gate and drain-lag effects are studied in (GaN)/InAlN/GaN and InAlN/AlN/GaN HEMTs grown on sapphire. Electron trapping on the surface states between the gate and the drain forming the net negative charge up-to similar to 2 x 10(13) cm(-2) is found to be responsible for the gate-lag effect in the (GaN)/InAlN/GaN HEMTs. If the polarization charge at the device surface is decreased by GaN capping, then density of the trapped charge is not changed, however the electron de-trapping process becomes faster. The drain-lag effect is caused by electron injection and trapping in the source-gate area reaching similar to 1 x 10(13) cm(-2) of the trapped charge in the steady state. In the studied voltage range the InAlN/AlN/GaN HEMT is shown to be gate-lag-free suggesting that this parasitic transient can be avoided if thin AlN is used in the epi-layer growth sequence. It is assumed that this breakthrough quality relates to the decreased or even reverted electric field in the MAIN layer if AlN is inserted. Surface states need not to be generated in this case. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Abstract: Ba-hexaferrite and Ni 0.5 Zn 0.5 ferrite nano composites have been successfully fabricated by a self-propagating combustion method. Transmission electron microscopy and X-ray diffractometer analysis showed that two ferrite phases were homogeneously distributed and the measured grain size of them around 20nm. The saturation magnetizations of the composites were revealed to be increased compared with the theoretical values. These increments of the saturation magnetization values could be explained by the exchange spring interaction between soft and hard magnetic phases.

Abstract: This paper reports the successful deposition of Cu3SnS4 thin films using a spray pyrolysis technique. These films were deposited on glass substrates using a solution containing CuCl2 · 2H2O, SnCl2 · 2H2O and SC(NH2)2 as precursors with appropriate chemical compositions of elements ([Sn] = 10–2 M and [Cu]/[Sn] = 2 × 2.2) at a substrate temperature of 360 °C. X-ray diffraction analysis show that unannealed and annealed Cu3SnS4 thin films under sulphur atmosphere crystallise in the tetragonal structure and the crystallites exhibit preferential (112) orientation of the grains. Optical measurements show that Cu3SnS4 sprayed thin film annealed at 500 °C has a direct band gap of about 1.22 eV. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Abstract: Surface plasmon (SP) coupling technique was used to enhance blue and green light emissions from InGaN/GaN quantum wells (QWs). Large enhancement of photoluminescence (PL) of both blue and green emissions was observed with silver coated samples, whereas the enhancements were not so effective for the gold coated samples. We could obtain well enhanced green emission by tuning the matching condition of QW-SP coupling with nano-grating structures at gold layers. This method should be useful to design even more efficient structures and to fabricate super bright light emitting devices.

Abstract: This work demonstrates a method for non-invasively monitoring the growth and Φ6 virus infection of Pseudomonas syringae bacteria using a 1-D porous silicon photonic crystal and a white-light source coupled to a CCD spectrometer. Bacteria growth on porous Si leads to increased scattering efficiency that can be measured as a change in intensity of light reflected from a 1-D porous Si photonic crystal. A linear relationship between bacteria concentration and intensity of light at the photonic resonance is observed, and detection limits are similar to those obtained from optical density measurements. Upon infection with virus, decreases in scattered light intensity are observed at times that correlate with cell lysis caused by viral replication and subsequent bursting of bacteria cells. It is shown that measurements can be performed in real-time and in an incubator where cells remain in their ideal environment throughout the experiment. This method is well-suited for cell-based biosensing, because bacteria cells can be monitored remotely without the need for sampling cells for plating or optical density measurements.

Abstract: A three-dimensional p-n diode structure is presented for the generation of energy via photovoltaic and betavoltaic modes of operation. Macroporous Silicon (MPS) has a large degree of internal surface area and its vertically oriented pores, which extend deep into the bulk of the Si substrate, allow for the creation of three-dimensional structures. In this device the MPS will not only serve as a means for creating 3D diode structures, it will also serve as a host matrix for a tritium isotope which emits energetic beta particles. By varying electrochemical etching conditions and using a prepatterning technique, 1.1 μm diameter pores with a spacing of 2.5 μm were achieved. The p-n junction was created using a rapid thermal process (RTP) which relies on the diffusion from an n-type solid source into the MPS. To ensure the quality of the diode structure, devices were tested using a light source which resulted in a photovoltaic response. Finally, betavoltaic operation was demonstrated by exposing devices to a tritium gas source. The average energy conversion efficiency of the first generation 3D diode was one order of magnitude higher than that of a similar planar device.

Abstract: We report on optical orientation experiments in undoped GaAsN epilayers and InGaAsN quantum wells (QW), showing that a strong electron spin polarisation can persist at room temperature. We demonstrate that the spin dynamics in these dilute nitride structures is governed by a spin-dependent recombination process of free conduction electrons on deep paramagnetic centres.

Abstract: Porous silicon (p-Si) has been investigated as a novel delivery system for protein therapeutics. The loading of a model hydrophilic protein, Papain into anodised and stain etched p-Si powders has been investigated using X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy (FTIR) and correlations made with the release kinetics. Variation in specific Papain (Amide I/II) and p-Si (Si–Hx) functional group absorbances with Papain loading level was characterised using FTIR, while the surface chemical distribution was assessed using XPS. A combination of burst release and sustained release of Papain was observed from p-Si powders; this was dependent on p-Si type and the Papain loading level. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Abstract: InGaN photovoltaic structures with p-n junctions have been fabricated by metal organic chemical vapour deposition. Using double-crystal X-ray diffraction measurements, it was found that the room temperature band gaps of p-InGaN and n-InGaN films were 2.7 and 2.8 eV, respectively. Values of 3.4 x 10(-2) mA cm(-2) short-circuit current, 0.43 V open-circuit voltage and 0.57 fill factor have been achieved under ultraviolet illumination (360 nm), which were related to p-n junction connected back-to-back with a Schottky barrier and many defects of the p-InGaN film. 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Abstract: New conditions for one-step ELO were implemented to grow coalesced (1120) non-polar and (1122) semi-polar GaN layers starting, respectively, from R- and M-plane sapphire A great part of the stacking faults (SFs) and dislocations are filtrated resulting in GaN material with better structural and optical properties In the ELO-like (1120) and (1122) films, the near band edge emission dominates photoluminescence spectra and is in the range 345-348 eV depending on lattice deformation The strongest emission is met for the semi-polar (1122) ELO When mask stripes are not normal to the c-axis, a singular ELO is developed with inclined coalescence facets However, in this case, SFs overgrow above the mask and so lead to poor optical properties, dominated by SF and dislocation related peaks In any case, the internal electric field reduction in (Al,Ga)N/GaN non- or semi-polar quantum-wells stacks is better viewed when the heterostructures are grown on ELO with stripes normal to the c-axis

Abstract: The total structural energy per primitive lattice cell, density of electron states, spatial distribution of electrons and elastic modulus in fcc Fe–H solid solutions are studied using the density functional theory and Wien2k program package. It is shown that hydrogen increases the density of electron states at the Fermi level. The density of conduction electrons is increased in the vicinity of hydrogen atoms, which suggests that the latter migrate over the crystal lattice surrounded by the clouds of conduction electrons. Calculations of elastic modulus show that hydrogen decreases the shear modulus c44. The consequences for mechanical properties of hydrogen-charged austenitic steels are analysed taking into account the stress for activation of dislocation sources, the line tension of dislocations and the distance between dislocations in pile-ups. It is concluded that hydrogen-induced brittleness of austenitic steels can be satisfactorily interpreted in terms of the hydrogen effect on the electronic structure. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Abstract: Detailed data about deoxyribonucleic acid (DNA) attachment, arrangement, density and functionality on mono-crystalline diamond surfaces are obtained by direct measurements in electrolytic solutions using fluorescence microscopy and atomic force microscopy in various regimes (oscillating, contact, phase, and surface potential imaging) and by fitting the data into a microscopic geometrical model of DNA. DNA is immobilized on undoped and boron-doped diamonds with hydrogen and oxygen surface terminations which were functionalized by aminodecene and nitrofenyl linker molecules. The data show that, except photochemically processed oxidized diamond surfaces, the DNA molecules are covalently linked to diamond in a 65-92 angstrom thin and highly dense layers (6 x 10(12) molecules/cm(2)) with sub-nanometer intermolecular spacing and a strong tilt of 31 degrees with respect to the surface. Ordering of these DNA layers shows only a weak (< 10%) response to a change of buffer salinity in the range of 1-300 mM. The data are discussed with view to biosensor applications. (C) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Abstract: Chemically modified Field Effect Transistor (ChemFET) sensor for ammonium (NF 4+ ) ions was developed from AlGaN/GaN High Electron Mobility Transistor (HEMT) structures (NH + 4 -ChemHEMT). The sensor consists of a HEMT device with non-metallized gate, which was coated with a polyvinyl chloride (PVC) membrane enriched with ammonium ionophore (Nonactin). The AlGaN/GaN -CNH + 4 -ChemHEMT with gate width of 100 μm and gate length of 100 μm exhibited a constant sensitivity of 55.5 mV/pNH + 4 for NH + 4 concentration in the range from 10 -5 M to 10 -2 M. The NH + 4 concentration detection limit was 5.4 x 10 -6 M, which is approximately one order of magnitude lower compared to Si based insulator gate ChemFETs. The sensor exhibited also sufficiently long storage lifetime, indicating the strong adhesion of the PVC membrane to the GaN(0001) surface.

Abstract: We report on three new types of nanoelectromechanical systems based on carbon nanotubes: an electromechanical nanothermometer, a nanorelay and a nanomotor. The nanothermometer can be used for accurate temperature measurements in spatially localized regions with dimensions of several hundred nanometers. The nanorelay is a prototype of a memory cell, and the nanoactuator can be used for transformation of the forward force into the relative rotation of the walls. Relative motion of the walls in these nanosystems is defined by the shape of the interwall interaction energy surface. Ab initio and semi-empirical calculations have been used to estimate the operational characteristics and dimensions of these nanosystems.

Abstract: We report on a scaleable synthesis route for highly luminescent silicon nanocrystal assemblies and demonstrate that their emission properties are identical to those known for other systems containing silicon nanocrystals. Structural investigations confirmed that chemically porosified metallurgical grade silicon powder consists of silicon nanocrystal assemblies having nanometer sizes characterized by very high total internal surface area. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Abstract: In this work, integration on the same chip of porous silicon gas sensors along with their driving/readout electronic circuits by using an industrial microelectronic process is demonstrated. To ensure maximum compatibility, the porous silicon formation is performed after the integrated circuit fabrication flow is completed. The chip contains three CMOS operational amplifiers, a band-gap voltage reference, an integrated temperature sensor and several porous silicon-based NO 2 sensors. The simultaneous functionality of the electronics and the sensor is demonstrated by using various circuit blocks to implement a simple driving/readout electronic interface for the sensor.

Abstract: Optical devices with micro- and nanooptical elements using polymers and, in particular nano-scaled organic–inorganic hybrid materials such as ORMOCER®s, will be beyond of the next generation of optical components. For the generation of photonic elements, 3D photonic bandgap materials have been proposed as the basis of many devices. In order to create complete 3D photonic bandgaps, materials enabling high refractive index contrast are needed. Combining suitable materials with highly sophisticated processing methods such as two-photon polymerization (2PP) using femtosecond lasers is a step towards novel photonic elements. The materials and the patterning process will be discussed with respect these applications. In order to demonstrate the potential of the 2PP method, different classes of materials are investigated. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)