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Electrochemical templating through porous membranes is applied to form arrays of micrometer long Ni nanowires (NWs). Detailed structural and electrochemical characterization, including electrochemi...

Energy storage using dielectric capacitors is a growing area of research and development. However, designing a highly performing dielectric capacitor is still a challenge. Despite the excellent results achieved in lead-based dielectrics, lead-free substitutes are essential because of the environmental concerns associated with lead-based products. The lead-free 1−x (0.94NaNbO3− 0.06SrZrO3)+ x Bi2O3 ceramics abbreviated NNSZ + xB for x = 0.0, 0.05, 0.1, 0.15, and 0.20 was fabricated via solid-state reaction. A recoverable energy density of 2.93 J cm−3 was obtained for NNSZ+0.1B, associated with high thermal stability (25–130 °C), excellent cycling (N = 105), and high efficiency (η) of 83.5%. Moreover, the introduction of Bi2O3 significantly improved the electrical insulation (ϵr at 1 kHz = 1608 and tan δ = 0.0038) and breakdown strength (380 kVcm−1) of NNSZ+0.1B by minimizing the formation of sodium, bismuth, and oxygen vacancies. The results obtained in this study provide a benchmark for further investigations on NaNbO3-based ceramics. More importantly, this study suggests that NNSZ + xB ceramics can be used in pulsed power technology.

The present study investigates the influence of two different manufacturing techniques on the mechanical behaviour of ZL111 aluminium expanded glass (EG) syntactic foam. Counter-gravity infiltration and stir casting methods were used to produce syntactic foams with 2–3 mm and 3–4 mm EG particles, as well as bulk samples. T6 heat treatment was used to alter the microstructure of the ZL111 alloy and, thus, to increase the strength of the specimens. All samples were tested using quasi-static compression and μCT analysis. The density of the produced foam samples varied from 1.03 g/cm3 to 1.33 g/cm3, while the 0.2 % offset yield strength varied between 18.83 MPa and 61.62 MPa. The stir casting technique yielded a closed-cell morphology and stronger syntactic foam samples overall. The metallic matrix of the infiltration casting samples exhibited open-cell morphology and the resulting foams had a decreased strength and density.

The 18CrNiMo7-6 steel billet was prepared by the process of EBT→LF→VD→die casting and forging. The position distribution, composition, type and cause of inclusions in the billet were statistically analysed by ASPEX and scanning electron microscopy. The results show that there are obvious distribution differences of inclusions in different parts of the steel billet. In contrast, the number density of inclusions in the billet corresponding to the ingot riser and the negative segregation zone is higher; the average composition point of the inclusions in the slow cooling zone tends to be distributed in the higher temperature zone of the MgO-Al2O3-CaO ternary phase diagram.

This study aims to compare the release profile of antibiotics when loaded onto a new mineralized collagen (MC) putty with conventional polymethyl methacrylate (PMMA) cement as well as their feasibility for clinical application for orthopaedic wounds. Two types of antibiotic-loaded implants were fabricated by physically mixing Imipenem or Vancomycin with either PMMA or MC in a quantifiable manner. Subsequently, the release profiles of antibiotics and their inhibitory effects on bacterial growth were evaluated both in vitro and in vivo. In comparison to PMMA, the antibiotic-loaded MC putty was easier to make with high flexibility of antibiotic selection based on drug sensitivity test, and surgeon friendly moldability. The inhibitory effects of bacterial growth lasted 24 h post-intramuscular implantation. The Imipenem-loaded MC putty was confirmed to be superior as a local drug delivery system (LDDS) over PMMA cement, the only type of antibiotics carrier orthopaedic clinics currently use.

Carbon/carbon (C/C) composites were doped by Zr and Zr2Cu respectively. The microstructures and ablation properties of two kinds of doped C/C composites were compared. The results indicate that the sweat cooling effect of Cu phase can improve the antiablation properties of the C/C–ZrC composites when Zr2Cu was used as the infiltrator.

Co ions with 100 keV energy with a fluence of 1 × 10(15) cm(-2) are implanted into ZnO(0001) single crystals at 300 °C under vacuum. The resulting Co-implanted ZnO single crystals and the subsequent 750 °C and 900 °C annealed samples are analysed with respect to their structural, optical, electronic, magnetic and ac electrical properties. Photoluminescence and X-ray photoelectron spectroscopy results indicate the signatures of the Co(2+) state and its substitution at the tetrahedrally coordinated Zn-sites. X-ray diffraction and X-ray photoelectron spectroscopy identify the presence of the ZnCo2O4 and Co3O4 phases in the 900 °C annealed sample. By comparing the resistance response of the identified phases towards different magnetic environments, the impedance spectroscopy results successfully identify two magnetic phases (ZnCo2O4 and Co3O4) and a paramagnetic (CoZn) phase for the 750 °C and 900 °C annealed samples, implying the extrinsic nature of room temperature ferromagnetism. The observed ferromagnetism in each sample is not of single origin, instead the mutual effects of the secondary phases embedded in the paramagnetic host matrix are in competition with each other.

Chromium slag is a hazardous waste, and its high-value-added comprehensive utilisation would be advantageous. High refractive index thin films were prepared on glass substrates by a hydrothermal method from chromium slag with different mineralisers. The samples were characterised by inductively coupled plasma, X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, an atomic force microscope, a transmission electron microscope and by film thickness and refractive index. The results show that a few Fe2O3, FeOOH, Al2O3, AlOOH or MgO crystals are formed, and most compounds of iron, aluminium, magnesium and chromium are still in amorphous state. The film materials are combined with a glass substrate by a chemical bond. The coordination ability of mineraliser anion and metal ion affects the sediment reaction rates. With NaClO3 or NaHCO3 as a mineraliser, the film surface is a perfect three-dimensional space orientation network sediment with fine twines and small pores. The thinner the film, bigger the refractive index will be. The films’ refractive index is mainly related to the film structure and non crystalline phase.

Using experiments and numerical simulations, we investigate the dewetting of thin liquid films on chemically patterned substrates. The patterns consist of long and narrow hydrophobic stripes, separated by larger hydrophilic domains. We characterize the morphology and dynamics of the dewetting front starting from an initially present dry-spot. Moreover, we study the distortion of the liquid film on the adjacent hydrophilic domains as a function of film thickness, hydrophobic contact angle and pattern dimensions. Implications of our results on the solution processing of organic electronic devices on chemically patterned surfaces are discussed.

With device dimension downscaling, the oxide thickness reduction less than 3 nm in a metal–oxide–semiconductor structure has led to important changes in degradation mechanisms and failure modes. After the first breakdown event of ultrathin gate oxides, the leakage current presents a less dramatic and noisy continuous breakdown mode called progressive breakdown. In this article, we characterize the overall breakdown process of ultrathin gate oxides as a randomized logistic degradation process with a random onset time. The explicit result of the lifetime distribution is derived on the basis of this logistic degradation model. A numerical example is provided to calculate the lifetime distribution. The simulated lifetime data of our model fits lognormal distribution better than the Weibull distribution, which agrees with the experimental work in literature. Copyright © 2012 John Wiley & Sons, Ltd.

This study is devoted to developing a numerical model of aluminium melt added as a gassing agent and then heated to a certain temperature to obtain metallic foam. First, a powerful data processing method, i.e. the lattice Boltzmann method on network, is studied. This model considers the variety of complex boundary conditions, the simple and multiphase fluid flow in complex geometries, the stabilisation of the foams, the influence of the parameters depending on the local fluctuations of the metal foam pressure and the mutual interactions between the bubbles inside this foam. Second, the Navier–Stokes equation is applied to elucidate the fluid flows in the liquid. In addition, the diffusion equation for the hydrogen transport, the distribution of temperature, the density and the kinetic equations are studied as well. The Boltzmann algorithm on network is applied to solve the incompressible Navier–Stokes equations. Finally, a three-dimensional simulation method and calculation algorithm to discretise the com...

Nanocrystalline supersaturated solid solutions were formed by mechanically alloyed Fe-28Al (in atom percent) from the elemental powder of iron and aluminum. Phase evolution, grain size and lattice strain of these powders were determined and discussed. A thermodynamic model was developed based on semi-experimental theory of Miedema to calculate the chemical driving force for phase evolution. The influence of thermodynamic driving forces, namely the Gibbs free energy of mixing, for the solid solution and the amorphous was discussed and corresponded to the sequence of phase formations during mechanical alloying.

Efficient plasmon-mediated excitation energy transfer between the CdSe/ZnS semiconductor quantum dots (QDs) across the silver nanowire array up to 560 nm in length is observed. The subwavelength imaging and spectral response of the silver nanowire arrays with near-field point-source excitations are revealed by theoretical simulations. Our studies demonstrate three advantages of the nanosystem: efficient exciton-plasmon conversion at the input side of the array through near-field strong coupling, directional waveguidance and resonant transmission via half-wave plasmon modes of the nanowire array, and subwavelength imaging at the output side of the array. These advantages allow a long-range radiative excitation energy transfer with a high efficiency and a good directionality.

The effect of CaF2–4LiF (1–5 mol.-%) on the phase structure, microstructure and dielectric properties of 0·9BaTiO3–0·1BiScO3 (0·9BT–0·1BS) ceramics has been investigated. The 0·9BT– 0·1BS with CaF2–4LiF dopant ceramics sintered at 1100°C show a pure perovskite structure. Results show that CaF2–4LiF dopant can improve the sintering ability of 0·9BT–0·1BS ceramics when CaF2–4LiF content is below 3 mol.-%. The ceramics with 3 mol.-%(CaF2–4LiF) sintered at 1100°C exhibit a high permittivity, low dielectric loss as well as flat ϵ′ v. temperature curve indicating a favourable temperature stability, which are listed as follows: ϵ′25 °C=1483, tan δ 25 °C=0·00309, Δϵ′/ϵ′25 °C ≤ ± 13% at 100 kHz, in the temperature range from –55 to 150°C. This low sintering temperature allows using relatively inexpensive internal electrodes in the production of future capacitors.

Cu pumping is a potential reliability issue for through silicon via (TSV) based 2.5D and 3D integration, due to the CTE mismatch between silicon and copper. In this paper, we report the reliability assessment of Cu pumping treated at different annealing conditions. Cu pumping is simulated by finite element method to compare the effect of the overburden layer. The pumping of TSVs having a diameter of 10 μm and a depth of 100 μm has been fabricated and characterized using a white light optical profiler. According to the thermal budget evaluation and TC, HTS and HAST test results, higher annealing temperature is beneficial to control the Cu pumping and improve the TSV reliability.

A mathematical model of the direct chill (DC) casting process for magnesium billets has been developed to predict the temperature in the billet, dummy block, and center pin using the commercial finite-element (FE) package, ABAQUS. Boundary conditions used for primary and secondary cooling and interfacial cooling between the billet and dummy block were defined based on the literature and knowledge of the physical phenomena occurring during the process. Temperatures in the billet, mold, and dummy block, as well as sump depth, were measured for a series of casting conditions during a plant trial conducted at Timminco Metals. The data obtained during the plant trial were used to “fine-tune” and validate the model for a variety of industrial casting conditions.

A new type of polyester polyol dispersion with good storage stability was prepared based on a hydrophilic monomer 5-sodium sulfodimethyl isophthalate (5-SIPM), and frequently-used monomers such as neopentyl glycol (NPG), dimethyl terephthalate (DMT), dimethyl phthalate (DMP) and trimethylolpropane (TMP) by the transpolycondensation and polycondensation method. The polyester polyol dispersion was characterized by FTIR and GPC. The proper content of these monomers were determined by the performance of polyester dispersion: the content of TMP was 15wt%, the content of NPG was 7.5wt% and the hydrophilic monomer 5-SIPM content was 5wt%. Two-component waterborne polyurethane (2K-WPU) coatings were prepared by Bayhydur® XP2487/1 and polyester polyol dispersions, which were stored before and after at 40 ° for 6 weeks, the prepared films have no differences in drying time, adhesion, pencil hardness, gloss and chemical resistance, the result also reveals that the polyester polyol dispersion have excellent storage stability resistance.

Single phase AlN nanowires are fabricated by a sublimation method. They were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), typical selected area electron diffraction (SAED) and high-resolution transmission electron microscopy (HRTEM). The SEM and TEM images show that most of the nanowires have diameters of about 10–60 nm. The crystal structure of AlN nanowires revealed by XRD, SAED and HRTEM shows the AlN nanowires have a wurtzite structure.

Microwave assisted molten salt synthesis (MAMSS) method was employed to synthesised Bi4Ti3O12 (BTO). The MAMSS can produce the anisotropic BTO grains at 600°C for 30 min. The increase in temperature and soaking time can make a plate-like grain of BTO more distinct. There are not obvious changes of the particles size when the salt content continues to increase. The anisotropy of the grain produced by NaCl–KCl chlorate is much more distinctive than that by Na2SO4–K2SO4 sulphate.

Void shape changes induced by electromigration pose reliability problems in Al-based interconnects. Recent observations have shown that a rounded void sometimes collapses to a transverse slit in an interconnect with bamboo-like grain structure. This article provides a linear stability analysis for a circular void that is only partially conductive in an otherwise infinite conductive medium. The relation between the inner conductivity (i.e., the conductivity of the medium in the void) and the critical remote electric field intensity, Ecr, for the linear stability of the void is established. It is proven that when the inner conductivity becomes zero, Ecr goes to infinity, and we can look upon the inner conductivity of a vacuum void as zero. That is why the vacuum circular void is linearly stable. It is also shown that when the inner conductivity is very small, the stability of a void is sensitive to it. From the computational results, we know that if the inner conductivity is 0.1% of that outside the void, t...

Si/Pd‐based contact schemes based on the solid‐phase regrowth (SPR) process have been developed to form low‐resistance ohmic contacts to n‐Al0.5In0.5P (Eg=2.3 eV) with a minimum contact resistivity of about 6×10−6 Ω cm2. The SPR process responsible for the ohmic contact formation was verified using cross‐sectional transmission electron microscopy. The contact resistivity of the Si/Pd‐based contacts remained in the range of 2–3×10−5 Ω cm2 after aging at 400 °C for 25 h. Furthermore, a lateral modulation disordering phenomenon as a result of the SPR process in the regrown AlInP layer has been observed. These ohmic contacts may be useful in some novel Al0.5In0.5P‐related device fabrication schemes.

An on‐chip aluminum interconnect carries an intense electric current at an elevated temperature, motivating atoms to diffuse in the solid state, and inducing voids that may cause an open failure. Recent observations have shown that a void sometimes collapses to a slit running nearly perpendicular to the electric current direction. Such a slit often lies inside a grain rather than along a grain boundary. An earlier calculation showed that diffusion on the void surface, driven by the electric current, can cause a circular void to translate in an infinite, isotropic interconnect. It was suggested recently that this solution may be unstable, and that two forces compete in determining the void stability: surface tension favors a rounded void, and the electric current favors a slit. A linear perturbation analysis, surprisingly, revealed that the translating circular void is stable against infinitesimal shape perturbation. Consequently, the slit instability must have resulted from finite imperfections. This article reviews the experimental and theoretical findings, and describes a numerical simulation of finite void shape change. We determine the electric field by a conformal mapping of complex variables, and update the void shape for a time step by a variational method. The simulation shows that a finite void shape imperfection or surface tension anisotropy can cause a void to collapse to a slit.

We report the observation of weak magnetism in superlattices of LaAlO3/SrTiO3 using beta-detected nuclear magnetic resonance. The spin lattice relaxation rate of Li-8 in superlattices with a spacer layers of 8 and 6 unit cells of LaAlO3 exhibits a strong peak near similar to 35 K, whereas no such peak is observed in a superlattice with spacer layer thickness of 3 unit cells. We attribute the observed temperature dependence to slowing down of weakly coupled electronic moments at the LaAlO3/SrTiO3 interface. These results show that the magnetism at the interface depends strongly on the thickness of the spacer layer, and that a minimal thickness of similar to 4-6 unit cells is required for the appearance of magnetism. A simple model is used to determine that the observed relaxation is due to small fluctuating moments (similar to 0.002 mu(B)) in the two samples with a larger LaAlO3 spacer thickness. DOI: 10.1103/PhysRevLett.109.257207

In this paper, a constitutive model of elasticity coupled with damage suggested by Lemaitre et al, [1] is used. The macroscopic stress-strain response of the model includes two stages: strain hardening and strain softening. The basic equation is derived for the anti-plane shear problem. Several lowest order asymptotic solutions are obtained, and assembled for the crack-tip fields.

The synthesized Nd fluoride nanocrystals exhibited different upconversion behaviors as dispersed and aggregated samples due to the different energy transfer mechanisms. When they were dispersed in water, the NaNdF(4) nanocrystals exhibited approximately 400 times stronger upconversion fluorescence than the NdF(3) nanocrystals. Remarkable upconversion behaviors were found when the nanocrystals were aggregated in the films. For the NdF(3) nanocrystals, the energy transfer processes (4)I(13/2)--(4)F(3/2)--(4)G(7/2) in the films generated avalanche upconversion emissions with a high slope of approximately 12.0, which could be due to the large avalanche cross relaxation rates and spectral broadening effect. In contrast, the spectral broadening effect in the NaNdF(4) NCs films increased the energy transfer (4)I(15/2)--(4)F(3/2)--(4)G(5/2) of the Nd(3+) ions, and induced a new upconversion emission at approximately 680 nm with the slope increased from 1.0 to 3.2.

The preparation of improved catalytic materials based on natural diatomite is reported. Aluminum incorporation by an atomic implantation methods yields supports with enhanced acidity. Nano-zeolite Y supported diatomite composite materials with a multimodao distribution of interconnected micro- meso- and macro pores were obtained by in situ crystallization. Materials were characterized by XRD, TEM, NH 3 -TPD and textural studies using nitrogen adsorption / desorption measurements. The catalytic performance was tested in the cracking of a heavy petroleum residue. The results show, that diatomite due to its large pores is a superior support for the preparation of supported catalysts for the cracking of heavy oil fraction containing bulky molecules. Atomic implantation of aluminum yields catalysts of the same catalytic performance as loading with acidic nano-sized zeolite HY.

In this paper, an asymptotic finite-deformation approach is made to the stress singularity at the tip of a crack for a particular class of harmonic materials. The stresses at the tip of a crack are derived.

A Ni/GaAs/Si(001) structure was used to investigate solid-phase reactions of Ni with GaAs and Si. Cross-sectional transmission electron microscopy and secondary-ion-mass-spectrometry depth profile data reveal that a Ni/GaAs/Si(001) structure converts to a crystalline GaAs/amorphous NiSi/Si(001) after low temperature (⩽350 °C) annealing. We demonstrate that the reaction is driven by the decomposition of a NixGaAs intermediate which is induced by the proximity of the Si substrate. Two models are suggested to explain the mechanism of a crystalline GaAs layer nucleated from NixGaAs on the amorphous NiSi layer.

We report the fabrication and characterization of well-defined gated Si microtip arrays with diamond-like carbon (DLC) apexes. It was found that for a 40/spl times/40 gated Si tip array with DLC apexes, an emission current density up to 0.23 A/cm/sup 2/ can be obtained at an applied gate voltage of 200 V. The turn-on gate voltage of the devices is fall in a range of 38-50 V.

We have developed low resistance (ρc∼1×10−6 Ω cm2) Ge/Pd‐based (the Au/Ge/Pd and the Ag/Ge/Pd contacts) Ohmic contact schemes processed at temperatures 150–175 °C to n‐GaAs (n∼1×1018 cm−3). The Ohmic contact formation mechanism can be rationalized in terms of the solid phase regrowth (SPR) principle and the interdiffusion between Au (or Ag) and Ge.

Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 – August 2, 2012.

By observing the luminescence micrographic images and measuring the decay behaviors of photoluminescence spectra, it is found that the blue light‐emitting porous silicon obtained by boiling water treatment behaves very similarly to the red light‐emitting sample. It is thus believed that the blue light emission is originated from the porous silicon skeleton rather than impurity contaminations. The achievement of blue light emission requires the proper control of the size of the Si nanostructures, effective passivation of the internal surfaces of porous silicon layer, and keeping a mechanically strong Si skeleton. A theoretical estimation and the experiments show that the simultaneous fulfillment of these conditions is quite critical, which explains the poor reproducibility of achieving blue emission experimentally.

We report that the intraspecific structural colouration variation of the beetle Torynorrhina flammea is a result of diffraction shifting manipulated by a multilayer sub-structure contained in a three-dimensional (3D) photonic architecture. With a perpendicularly 2D quasiperiodic diffraction grating inserted into the multilayer, the 3D photonic structure gives rise to anticrossing bandgaps of diffraction from the coupling of grating and multilayer bands. The angular dispersion of diffraction induced by the multilayer band shift behaves normally, in contrast to the 'ultranegative' behaviour controlled by the quasiperiodic grating. In addition, the diffraction wavelength is more sensitive to the multilayer periodicity than the diffraction grating constant, which explains the 'smart' biological selection of T. flammea in its intraspecific colouration variation from red to green to blue. The elucidated mechanism could be advantageous for the potential exploration of novel dispersive optical elements.

In this work, based on wide bandgap Ga2O3 films, we demonstrated a fully transparent bipolar resistive random access memory (RRAM) device with very high average transmittance of 91.7% in the visible region. The semiconducting In-Ga-Zn-O (IGZO) films were used as symmetric electrodes to reduce sneak current. Different I-V performance will introduce a change in the overall oxygen vacancy distribution by an opposite polarity of electroforming voltage. The temperature dependent of I-V characteristics will be fitted to the hopping conduction mechanism for both of the high-resistance states (HRS) and low-resistance states (LRS) with semiconducting nature. The activation energy and trap spacing of LRS were lower and shorter than that of HRS. A model of resistive switching mechanism related to correlated barrier hopping theory has been proposed for the fully transparent IGZO/Ga2O3/IGZO RRAM device.

BiFeO3 thin films were epitaxially grown on (001) GaAs substrate by pulsed laser deposition with Nb doped SrTiO3 as a buffer layer. Piezoresponse force microscopy images exhibit effective ferroelectric switching of the heterostructure. The temperature-dependent current-voltage characteristics of the heterostructure reveal a resistance switching phenomenon and diode-like behavior with a rectifying ratio of 2 × 102 at the applied voltage of ±13.4 V. The electrical transport mechanism in the heterostructure has been illustrated by constructing the energy band structure. In addition, the resistance switching behavior in the heterostructure could be explained by the polarization modulation of the depletion region at the interface of the semiconductor and the ferroelectric layers.

The modified Peirel–Nabarro model of dislocations is not valid for the superdislocation bounded by the antiphase domain boundaries in long-range ordered intermetallic. In this work, a new Peirel–Nabarro Stress model is developed to take into account the critical resolved shear stress of antiphase domain boundary (APDB). Based on it, the Peirel–Nabarro Stress of DO3 structure and B2 structure in iron aluminides are calculated. Comparing the Peirel–Nabarro Stress of dislocations and the crystal theoretical yield strength, the results demonstrate B2-type crystal has good plasticity. It coincides with the experimental results well.

An aluminum interconnect can fail by a transgranular slit. We show how a rounded void collapses to such a slit, as atoms diffuse on the void surface, driven by electric current, thermal stress, and surface energy. We use a variational principle to simulate the shape evolution, and identify the critical conditions to trigger the shape instability.

Through a post treatment of light emitting porous silicon in boilingwater, a large blue shift of its photoluminescence (PL) spectrum hasbeen observed and a stable blue-green light emission at the peak wavelength down to 500 nm is achieved. The effect of boiling water treatment is suggested to be a kind of oxidation, which could reduce thesize of the Si column, fill up some micropores and strengthen the Siskeleton. The photoluminescence microscopic observation shows that the surface of blue light emitting porous silicon is composed of manysmall uniformly light-emitting domains at the size of several tens of μm. Fourier transform infrared reflection (FTIR) measurements show that the formation of Si-H bonds is not responsible for the visible luminescence in the very thin Si wires.

Spherical phosphors BaWO4 doped with rare-earth ions (RE = Eu, Tb, Tm) were prepared by the polyol method. The crystal structure and morphology of the powders were investigated using X-ray diffraction, field emission scanning electron microscopy and Fourier transform spectroscopy. The as-prepared BaWO4-based phosphors processed as low as 160 ?C show mono-dispersive and highly crystalline nanostructure. The optical characteristics of the phosphors were investigated using low-voltage cathodoluminescence. Efficient energy transfer between the host and RE ions were revealed in the spectra. Red, green and blue cathodoluminescence were observed corresponding to sharp dominant emission peaks located at 616 nm, 545 nm and 473 nm for Eu3+, Tb3+ and Tm3+ doped phosphors, respectively. Those peaks are attributed to the characteristic emission from Eu3+ (5D0 ? 7FJ transitions), Tb3+ (5D3 ? 7FJ and 5D4 ? 7FJ transitions) and Tm3+ (1D2 ? 3F4 and 1D2 ? 3H4 transitions) under low-voltage (?5 kV) excitation of electron beam. Luminescent intensities in the annealed BaWO4-based phosphors were significantly enhanced. The characteristics of the phosphors are investigated in terms of luminance, chromaticity and color purity. Fundamental mechanisms responsible for the low-voltage cathodoluminescence of BaWO4-based phosphors are discussed.

The authors report the fabrication and characterization of vacuum microdiode arrays using Si microtip with uniform diamondlike-carbon (DLC) apexes. The technique is based on the mass production procedure of integrated circuit devices. The typical turn-on voltage of the microdiode arrays is 50V, and it can provide emission current density up to 0.24A∕cm2 at 210V. The developed diodes with coated apexes considerably surpass the diodes with virgin Si tip (98V∕0.058A∕cm2) in their performance. Thus, the microdiode with DLC coatings on Si tip apexes are attractive for applications in charge neutralizers and microwave amplifiers. The underlying physics responsible for the device operation is discussed.

The mechanical behavior of rock mass is affected strongly by its material properties. This paper carries out statistical analyses of the material properties of a rock mass. Statistical analyses of the material constants and the initial damage parameter of the rock mass are performed by using both field and laboratory test data. Based on the measured properties of rock specimens, the elastic modulus, uniaxial compressive strength, and the Poisson's ratio of rock are each found to have normal distributions and the tensile strength to have the gamma distribution. By using Monte Carlo simulation, the equivalent critical tensile strain is found to have the normal distribution. The initial damage of the rock mass, which describes the effects of naturally existing geological discontinuities in a rock mass, is estimated using the field-measured longitudinal and transverse elastic wave velocities. It is found to have the beta distribution. These distributions of rock properties can be used in statistical analyses of the rock mass responses to both static and dynamic loads.

A Au (1000 A)/Ge (100 A)/Pd (100 A) contact scheme has been investigated to form low resistance Ohmic contact to n‐Al0.5In0.5P (Eg=2.3 eV) with a minimum contact resistivity of about 1×10−6 Ω cm2. The surface morphology of this contact remained smooth after annealing at 425 °C for 1 min. Front side secondary ion mass spectrometry depth profiles of this contact structure under different annealing conditions were performed. It is found that the outdiffusion of indium due to the reactions between the metallization and the Al0.5In0.5P substrate in conjunction with the indiffusion of Ge into the substrate is responsible for the Ohmic contact formation. The germanide formation is believed to be responsible for the smooth surface morphology. The contact resistivity of this contact remained ∼2×10−6 Ω cm2 after aging at 350 °C for 31 h.

We report that a Au/Ge/Pd layered structure can result in low contact resistivities (∼10−6 Ω cm2) to n‐GaAs processed in three temperature ranges (175–200, 340–350, and 425–450 °C). The contacts processed below the Au–Ge eutectic temperature (361 °C) show good surface and interface morphology, thermal stability, Au wire bondability, and reproducibility. The ohmic contact formation mechanisms are also presented.

We report the ohmic contact formation mechanism of the low resistance (∼1×10−6 Ω cm2) Au/Ge/Pd contact to n‐GaAs annealed at 175 °C. Cross‐sectional transmission electron microscopy and Rutherford backscattering spectrometry were utilized in this study. It is found that the solid phase regrowth process, interdiffusion between Au and Ge, and the enhancement of the conductivity of the excess Ge layer are responsible for the observed low contact resistivity.