bluuebunny/crossref_metadata_2025 huggingface dataset:
Mask pattern interference in AlGaInAs selective area metal-organic vapor-phase epitaxy: Experimental and modeling analysis
Authors: Dupuis N. , Décobert J. , Lagrée P.-Y. , Lagay N. , Poingt F. , Kazmierski C. , Ramdane A. , Ougazzaden A.
Published: June 2008

We studied selective area growth modeling and characterization of the AlGaInAs material system. We used a three-dimensional vapor phase diffusion model to extract the effective diffusion lengths of Al, Ga, and In species from measured thickness profiles of the three binaries AlAs, GaAs, and InP. Our growth conditions yield to 50, 85, and 10 μm for Al, Ga, and In, respectively. Based on these values, we achieved a precise prediction of AlGaInAs thickness, composition, band gap, and biaxial strain variations in different selective area growth conditions. Particular attention was paid to the influence of neighboring cells in the case of high mask density. This configuration occurs in practical component mask layout. High mask density leads to interferences between masked cells and enhances the effect of the long diffusion length of aluminum and gallium species. Then, the biaxial strain is tensile shifted and the band gap is blue shifted in the vicinity of a mask, compared to reference material features grown away from the mask. High-resolution micro-photoluminescence and optical interferometer microscopy measurements confirmed the validity of simulated band gap and thickness variations for both bulk and multi-quantum well layers.
Texture of NiSi films on Si(001), (111), and (110) substrates
Authors: Detavernier C. , Jordan-Sweet J. , Lavoie C.
Published: June 2008

Synchrotron radiation was used to study the texture of poly-crystalline NiSi films that were formed by a solid state reaction between a 30 nm Ni film and Si(001), (111), and (110) substrates. All films were strongly textured, and the different texture components were identified. Apart from the spots and/or circles characteristic of epitaxy or fiber texture, the pole figures contained symmetrical, though complex, patterns of lines. These lines are characteristic of axiotaxy, whereby NiSi grains preferentially align their (211)- or (202)-type planes parallel to Si(110)-type planes in each of the substrates. Since the spacing between NiSi(211) or NiSi(202) planes is almost identical to the spacing of 1.920 Å between Si(220) planes, the alignment of these planes results in a boundary structure that is periodic along a single direction in the plane of the interface. Intensity variations along the lines on the pole figures are also explained by the degree of periodicity of the interface. The brightest spots on the lines correspond to interface structures for which periodicity is achieved along two independent directions within the plane of the interface.
Electron holography analysis of a shallow junction for planar-bulk metal-oxide-semiconductor field-effect transistors approaching the scaling limit
Authors: Ikarashi Nobuyuki , Ikezawa Takeshi , Uejima Kazuya , Fukai Toshinori , Miyamura Makoto , Toda Akio , Hane Masami
Published: June 2008

We investigated electrostatic potential distributions in source∕drain extensions (SDEs) in metal-oxide-semiconductor field-effect transistors (MOSFETs) fabricated using state-of-the-art junction formation technology. We first demonstrate that electron holography can directly reveal potential distribution in scaled MOSFETs when specimen preparation artifacts are reduced, which we did by using back side low-energy Ar ion milling. Second, we examine the potential distributions in SDEs in a scaled (30-nm-gate-length) MOSFET fabricated by using a combination of cluster B implantation, millisecond annealing, and multihalo implantation. The results show that these junction formation technologies enable fabrication of very abrupt and shallow (10-nm-deep) SDE junctions. In addition, our experimental analysis, in conjunction with a Monte Carlo doping-process simulation, indicates that B channeling along the ⟨110⟩ direction of the Si substrate during the implantation process significantly blurs the SD junction profiles and that multihalo implantation can increase junction abruptness. Third, we show that our experimental results describe well the roll-off characteristics of the MOSFETs.
Modeling self-annealing kinetics in electroplated Cu thin films
Authors: Stangl M. , Militzer M.
Published: June 2008

Electroplated Cu films exhibit a microstructure evolution at room temperature, called self-annealing. The kinetics of this recrystallization process is strongly influenced by plating conditions in the form of Cu film thickness, current density, and additive content in the electrolyte. Existing models have been used and improved to describe the kinetics of self-annealing. This gives the possibility to evaluate the influence of processing parameters and predict self-annealing behavior of electroplated Cu thin films.
Linear scaling multireference singles and doubles configuration interaction
Authors: Chwee Tsz S. , Szilva Andrew B. , Lindh Roland , Carter Emily A.
Published: June 2008

A linear scaling multireference singles and doubles configuration interaction (MRSDCI) method has been developed. By using localized bases to span the occupied and virtual subspace, local truncation schemes can be applied in tandem with integral screening to reduce the various bottlenecks in a MRSDCI calculation. Among these, the evaluation of electron repulsion integrals and their subsequent transformation, together with the diagonalization of the large CI Hamiltonian matrix, correspond to the most computationally intensive steps in a MRSDCI calculation. We show that linear scaling is possible within each step. The scaling of the method with system size is explored with a system of linear alkane chains and we proceed to demonstrate this method can produce smooth potential energy surfaces via calculating the dissociation of trans-6-dodecene (C12H24) along the central CC bond.
Effects of diffraction and dispersion on acoustic radiation-induced static pulses
Authors: Cantrell John H.
Published: June 2008

It is shown that the shapes of acoustic radiation-induced static strain and displacement pulses are defined locally by the energy density of the generating waveform and that diffraction and attenuation produce dramatic changes in the shape of static displacement pulses when using laser detection. The effects of dispersion on static pulses are obtained by including a dispersive term in the phase of the particle velocity solution to the nonlinear wave equation. The dispersion causes an evolutionary change in the shape of the energy density profile that leads to the generation of solitons experimentally observed in fused silica.
Non-imprisonment conditions on spacetime
Authors: Minguzzi E.
Published: June 2008

The non-imprisonment conditions on spacetimes are studied. It is proved that the non-partial imprisonment property implies the distinction property. Moreover, it is proven that feeble distinction, a property which stays between weak distinction and causality, implies non-total imprisonment. As a result the non-imprisonment conditions can be included in the causal ladder of spacetimes. Finally, totally imprisoned causal curves are studied in detail, and results concerning the existence and properties of minimal invariant sets are obtained.
Three-band quantum well infrared photodetector using interband and intersubband transitions
Authors: Alves F. D. P. , Amorim J. , Byloos M. , Liu H. C. , Bezinger A. , Buchanan M. , Hanson N. , Karunasiri G.
Published: June 2008

This paper presents the design, fabrication, and characterization of a quantum well infrared photodetector capable of detecting near infrared (NIR), midwavelength infrared (MWIR), and long wavelength infrared (LWIR) simultaneously. The NIR detection was achieved using interband transition while MWIR and LWIR were based on intersubband transition in the conduction band. The quantum well structure was modeled by solving self-consistently the Schrödinger and Poisson equations with the help of the shooting method. Intersubband absorption in the sample was measured for the MWIR and LWIR using Fourier transform infrared spectroscopy, and the measured peak positions were found at 5.3 and 8.7 μm, respectively, which are within 5% of the theoretical values, indicating the good accuracy of the self-consistent model. The photodetectors were fabricated using a standard photolithography process with exposed middle contacts to allow separate bias and readout of signals from the three wavelength bands. The background limited infrared performance for the LWIR quantum wells shows an upper operating temperature of about 70 K, limiting the overall device. Photocurrent spectroscopy was performed and gave three peaks at 0.84, 5.0, and 8.5 μm wavelengths with approximately 0.5, 0.03, and 0.13 A/W peak responsivities for NIR, MWIR, and LWIR bands, respectively. These results demonstrate the possibility of detection of widely separated wavelength bands, in a single pixel device, using interband and intersubband transitions in quantum wells.
Magnon drag effect as the dominant contribution to the thermopower in Bi0.5−xLaxSr0.5MnO3 (0.1≤x≤0.4)
Authors: Kim Byung Hoon , Kim Jun Sung , Park Tae Hoi , Lee Dea Su , Park Yung Woo
Published: June 2008

The temperature-dependent thermopower S(T) of Bi0.5−xLaxSr0.5MnO3 (0.1≤x≤0.4) (BLSMO) has been investigated in this study. The density of state at the Fermi level as a function of the La concentration is obtained via the equation for the diffusion thermopower (TEP) in the low-temperature regime. An equation that takes into account the diffusion, phonon drag, and magnon drag contributions to the TEP was established. With this equation, each component of the TEP is extracted and compared in the intermediate temperature regime. It was determined that the phonon drag contribution of the TEP is closely related to the La concentration dependence of the lattice parameters and that the magnon drag component contributes predominantly to the thermopower of BLSMO in the intermediate temperature regime.
Metal-semiconductor-metal photodetectors based on single-walled carbon nanotube film–GaAs Schottky contacts
Authors: Behnam Ashkan , Johnson Jason , Choi Yongho , Noriega Leila , Ertosun M. Günhan , Wu Zhuangchun , Rinzler Andrew G. , Kapur Pawan , Saraswat Krishna C. , Ural Ant
Published: June 2008

We demonstrate the Schottky behavior of single-walled carbon nanotube (CNT) film contacts on GaAs by fabricating and characterizing metal-semiconductor-metal (MSM) photodetectors with CNT film electrodes. We extract the Schottky barrier height of CNT film contacts on GaAs by measuring the dark I-V characteristics as a function of temperature. The results show that at temperatures above ∼260 K, thermionic emission of electrons with a barrier height of ∼0.54 eV is the dominant transport mechanism in CNT film–GaAs junctions, whereas at lower temperatures, tunneling begins to dominate suggested by the weak dependence of current on temperature. Assuming an ideal MS diode, this barrier height corresponds to a CNT film workfunction of ∼4.6 eV, which is in excellent agreement with the previously reported values. Furthermore, we characterize the effect of device geometry on the dark current and find that dark currents of the MSM devices scale rationally with device geometry, such as the device active area, finger width, and finger spacing. Finally, we compare the dark and photocurrent of the CNT film-based MSM photodetectors with standard metal-based MSMs. We find that MSM devices with CNT film electrodes exhibit a higher photocurrent-to-dark current ratio while maintaining a comparable responsivity relative to metal control devices. These results not only provide valuable information about the fundamental properties of the CNT film–GaAs interface but also open up the possibility of integrating CNT films as transparent and conductive Schottky electrodes in conventional semiconductor electronic and optoelectronic devices.
Type II transition in InSb-based nanostructures for midinfrared applications
Authors: Intartaglia R. , Rainó G. , Tasco V. , Della Sala F. , Cingolani R. , Baranov A. N. , Deguffroy N. , Tournié E. , Satpati B. , Trampert A. , De Giorgi M.
Published: June 2008

We present a study of the structural and optical properties of a heterostructure emitting in the midinfrared. The structure consists of monolayerlike InSb quantum wells inserted in an InAs∕GaSb superlattice (SL) matrix. X-ray diffraction and transmission electron microscopy analyses show a high structural quality of the structure. A strong emission line with a peak energy near 0.30eV (3.5μm) is observed from the monolayerlike InSb. In order to identify the physical origin of this transition, excitation density and temperature dependent photoluminescence experiments have been performed on samples with different nominal InSb thicknesses and SL designs. The experimental results suggest a type II band alignment, with electrons localized in the conduction miniband of the InAs∕GaSb SL matrix and holes localized in the monolayerlike InSb. This assignment is supported by the shift of InSb layer emission to lower energies when the SL design is changed, and by tight-binding calculations.
Hopping approach towards exciton dissociation in conjugated polymers
Authors: Emelianova E. V. , van der Auweraer M. , Bässler H.
Published: June 2008

By employing random walk an analytic theory for the dissociation of singlet excitons in a random organic solid, for instance, a conjugated polymer, has been developed. At variance of conventional three-dimensional Onsager theory, it is assumed that an exciton with finite lifetime can first transfer endothermically an electron to an adjacent site, thereby generating a charge transfer state whose energy is above the energy of that of the initial exciton. In a second step the latter can fully dissociate in accordance with Onsager’s concept Brownian motion. The results indicate that, depending of the energy required for the first jump, the first jump contributes significantly to the field dependence of the dissociation yield. Disorder weakens the temperature dependence of the yield dramatically and precludes extracting information on the exciton binding energy from it.
Thermal conduction in molecular chains: Non-Markovian effects
Authors: Segal Dvira
Published: June 2008

We study the effect of non-Markovian reservoirs on the heat conduction properties of short to intermediate size molecular chains. Using classical molecular dynamics simulations, we show that the distance dependence of the heat current is determined not only by the molecular properties, rather it is also critically influenced by the spectral properties of the heat baths, for both harmonic and anharmonic molecular chains. For highly correlated reservoirs the current of an anharmonic chain may exceed the flux of the corresponding harmonic system. Our numerical results are accompanied by a simple single-mode heat conduction model that can capture the intricate distance dependence obtained numerically.
Path integral Monte Carlo study of CO2 solvation in He4 clusters
Authors: Li Zheng , Wang Lecheng , Ran Hong , Xie Daiqian , Blinov N. , Roy P.-N. , Guo Hua
Published: June 2008

We present a finite temperature quantum mechanical study of the dynamical and structural properties of small HeN4–CO2 clusters (N⩽17) using a path integral Monte Carlo (PIMC) method. The simulations were based on a He–CO2 interaction potential with explicit dependence on the asymmetric stretch of the CO2 molecule obtained at the CCSD(T) level. The shift of the CO2 antisymmetric stretching (ν3) band origin and effective rotational constant were calculated as a function of the cluster size. In excellent agreement with experimental observations, the CO2 vibrational band origin shifts and rotational constant show a turnaround near N=5, corresponding to a donut structure with the He atoms in equatorial positions of the linear dopant molecule.
Density functional study of CO adsorption on Scn (n=2–13) clusters
Authors: Wu Guangfen , Wang Jinlan , Lu Yiming , Yang Mingli
Published: June 2008

The adsorption properties of a single CO molecule on Scn (n=2–13) clusters are studied by means of a density functional theory with the generalized gradient approximation. Two adsorption patterns are identified. Pattern a (n=3, 4, 6, 8, 11, and 12), CO binds to hollow site while Pattern b (n=5, 7, 9, 10, and 13), CO binds to bridge site accompanied by significantly lengthening of the Sc–Sc bond. The adsorption energy exhibits clear size-dependent variation and odd-even oscillation for n<10 and reach the peak at n=5, 7, and 9, implying their high chemical reactivity. Similar variations are noted in C–O bond length, vibrational frequency, and charge transferred between CO and the clusters. This can be understood in light of the adsorption pattern, the atomic motif, and the relative stability of the bare Sc clusters. Compared with the free Sc clusters, the magnetic nature remains upon adsorption except n=2, 4, 12, and 13. Particularly, the moments of n=13 reduce significantly from 19 to 5μB, implying the adsorption plays an attenuation influence on the magnetism of the cluster.
Block correlated coupled cluster method with a complete-active-space self-consistent-field reference function: The formula for general active spaces and its applications for multibond breaking systems
Authors: Fang Tao , Shen Jun , Li Shuhua
Published: June 2008

The block correlated coupled cluster (BCCC) theory is developed for a general complete-active-space (CAS) self-consistent-field reference function. By truncating the cluster operator up to the four-block correlation level, we derive the spin orbital formulation of the CAS-BCCC4 approach. The CAS-BCCC4 approach is invariant to separate unitary transformation within active, occupied, and virtual orbitals. We have implemented the approach and applied this approach to describe the potential energy surfaces for bond breaking processes in C2 and N2 and for a simultaneous double bond dissociation in H2O. Numerical results show that the CAS-BCCC4 approach provides quite accurate descriptions for the entire dissociation process in each of the studied systems. The overall performance of the present approach is found to be better than that of the internally contracted multireference configuration interaction singles and doubles or complete-active-space second-order perturbation theory. The size-extensivity error is found to be relatively small for N2.
A newab initiopotential-energy surface for NH2(XA″2) and quantum studies of NH2 vibrational spectrum and rate constant for the N(D2)+H2→NH+H reaction
Authors: Zhou Shulan , Xie Daiqian , Lin Shi Ying , Guo Hua
Published: June 2008

A new global potential-energy surface for the ground electronic state of NH2(XA″2) has been constructed by three-dimensional cubic spline interpolation of more than 20 000 ab initio points, which were calculated at the multireference configuration-interaction level with Davidson correction using the augmented correlation-consistent polarized valence quadruple-zeta basis set. The new potential is shown to yield better overall agreement with the experimental vibrational frequencies of NH2 and its isotopomers. In addition, the rate constant for the N(D2)+H2(XΣg+1)→NH(XΣ−3)+H(S2) reaction was calculated up to 600K and the agreement with experimental data is substantially improved over previous results.
The LaFe11.2Co0.7Si1.1Cx carbides for magnetic refrigeration close to room temperature
Authors: Balli Mohamed , Fruchart Daniel , Gignoux Damien
Published: June 2008

The influence of carbon on the structural, magnetic, and magnetocaloric properties of LaFe11.2Co0.7Si1.1Cx compounds was investigated. The Curie temperature increases with increasing the carbon content. The maximum magnetic entropy changes under a magnetic field change of 5T are about 14.5, 9.8, and 8.3J∕kgK for x=0.1, 0.2, and 0.3, respectively. A composite material based on LaFe11.2Co0.7Si1.1Cx was proposed for magnetic systems using Ericsson cycle for refrigeration close to room temperature. The obtained entropy change of the composite remains approximately constant in this temperature range.
First-principles study for transport properties of armchair carbon nanotubes with a double vacancy under strain
Authors: Li Zi , Wang Chong-Yu , Zhang Xu , Ke San-Huang , Yang Weitao
Published: June 2008

Vacancies are one of the most important defects in carbon nanotubes (CNTs). Vacancies could affect the mechanical, chemical, and electronic properties of CNTs. In this study, we first use first-principles plane-wave calculation to optimize the structure of single-walled CNTs with a double vacancy under 0%, 3%, and 6% strains, respectively. Then, we use the single-particle Green function method to calculate their transport properties. It is found that different strains cause different local structures near the defect, which change the transmission function around the Fermi energy, and the conductance tends to be maximized under ∼3% strain.
Nonstandard analysis and jump conditions for converging shock waves
Authors: Baty Roy S. , Farassat F. , Tucker Don H.
Published: June 2008

Nonstandard analysis is an area of modern mathematics that studies abstract number systems containing both infinitesimal and infinite numbers. This article applies nonstandard analysis to derive jump conditions for one-dimensional, converging shock waves in a compressible, inviscid, perfect gas. It is assumed that the shock thickness occurs on an infinitesimal interval and the jump functions in the thermodynamic and fluid dynamic parameters occur smoothly across this interval. Predistributions of the Heaviside function and the Dirac delta measure are introduced to model the flow parameters across a shock wave. The equations of motion expressed in nonconservative form are then applied to derive unambiguous relationships between the jump functions for the flow parameters.
Hydrogen plasma and atomic oxygen treatments of diamond: Chemical versus morphological effects
Authors: Shpilman Z. , Gouzman I. , Grossman E. , Akhvlediani R. , Hoffman A.
Published: June 2008

Chemical bonding and morphology of chemical vapor deposited diamond films were studied using high resolution electron energy loss spectroscopy and atomic force microscopy, following hydrogen plasma and atomic oxygen exposures. The hydrogen plasma exposure resulted in preferential etching of nondiamond carbon phases, selective etching of diamond facets, and termination of the diamond surfaces by sp3-C–H species. Exposure to atomic oxygen, on the other hand, produced significant chemical changes resulting in oxidized hydrocarbon ill defined top layer, while the morphology of the surface remained almost unchanged.
Magnetostatic interactions between carbon nanotubes filled with magnetic nanoparticles
Authors: Kornev Konstantin G. , Halverson Derek , Korneva Guzeliya , Gogotsi Yury , Friedman Gary
Published: June 2008

The magnetostatic interactions between carbon nanotubes filled with magnetic particles have been experimentally and theoretically studied. By making nanotubes uniformly magnetized, one eliminates the attraction caused by periodicity of nanoparticles in magnetic chains. The discreteness of individual nanoparticles in the nanoneedles is not observed and these nanoneedles interact by their magnetic poles. Since the attraction/repulsion events are predictable, the suspensions of magnetic nanotubes are attractive candidates for active elements in changeable diffraction gratings, filters, and polarizers.
Effect of electron energy distribution function on the global model for high power microwave breakdown at high pressures
Authors: Nam Sang Ki , Verboncoeur John P.
Published: June 2008

A global model (GM) was developed to investigate the effect of reaction kinetics and plasma parameters on high power microwave (HPM) breakdown time for multiple species. However, the GM requires specification of the electron energy distribution function (EEDF); the common assumption of a Maxwellian EEDF results in incorrect plasma parameters since the electrons are not in equilibrium. We examine the effect of the EEDF on the GM and develop a method to obtain a better EEDF to improve the fidelity of the prediction of HPM breakdown at high pressures.
Observation of giant photocurrent gain in highly doped (In,Ga)N∕GaN multiple-quantum-well-based photodiodes
Authors: Rivera C. , Muñoz E.
Published: June 2008

The authors report on the observation of a giant photocurrent gain (>106) in highly doped (In,Ga)N∕GaN multiple-quantum-well-based photodiodes, which decreases with temperature. This large photocurrent gain appears at low forward bias and strongly depends on the current transport mechanism. Results of capacitance-voltage measurements show that the photocurrent gain is related to the screening of the built-in electric field by charge accumulation. The role of the (Al,Ga)N electron blocking layer in current transport has been studied by comparing samples nominally identical except for the existence of this layer.
Enhanced performance of organic light-emitting diodes with an air-stable n-type hole-injection layer
Authors: Chu Ta-Ya , Kwong C. Y. , Song Ok-Keun
Published: June 2008

An air-stable n-type organic semiconductor, N,N-bis(4-trifluoromethoxybenzyl)-1,4,5,8-naphthalene-tetracarboxylic di-imide (NTCDI-OCF3), can function as an excellent hole-injection layer to improve the hole injection from an indium tin oxide (ITO) anode to a hole-transporting layer (HTL). Significantly improved hole injection was achieved by introducing an ultrathin layer of NTCDI-OCF3 between ITO and HTL, leading to a lower operational voltage and relatively less power consumption. The results can be attributed to the reduced hole-injection energy barrier from ITO to HTL, as shown by x-ray photoelectron spectroscopy measurements, due to the surface dipole that is formed by the NTCDI-OCF3. The thickness dependence of NTCDI-OCF3 was also examined.
Rashba spin-orbit effect on the zero conductance and the magnetoresistance of a quantum ring
Authors: Dong Yan-Kun , Li Yu-Xian
Published: June 2008

Using a mode matched scattering matrix method, we study the effect of Rashba spin-orbit coupling and a tunnel barrier on the zero conductance and the tunnel magnetoresistance (TMR) in a one-dimensional conducting Aharonov–Bohm ring symmetrically coupled to two ferromagnetic leads. It is found that the conductances of spin-up and spin-down electrons show periodic variations as the ring’s length changes. The conductance amplitude in antiferromagnetic alignment is very different from that in ferromagnetic alignment. The lifting of the real zero conductance is changed by the spin-orbit interaction and the tunnel barrier. The numerical results also show that this structure can provide a large TMR. When the ring’s length is increased, the TMR varies its period.
Neutron diffraction study of hexagonal manganite YMnO3, HoMnO3, and ErMnO3 epitaxial films
Authors: Gélard I. , Dubourdieu C. , Pailhès S. , Petit S. , Simon Ch.
Published: June 2008

The antiferromagnetic phase transition in epitaxial RMnO3 (R=Y,Ho,Er) films of thickness 450–500nm was investigated by neutron diffraction by recording the intensity variation of magnetic reflections as a function of temperature. For YMnO3 and ErMnO3, the Néel temperature for the Mn3+ ions ordering is of 66 and 68K, respectively. For HoMnO3, the magnetic 011 reflection, which normally appears in bulk, is very weak and thus the onset of the Mn3+ ordering is not clearly observed; at 50K there is a magnetic phase transition, which temperature corresponds to the reorientation temperature in bulk HoMnO3.
Segregation of oxygen vacancy at metal-HfO2 interfaces
Authors: Cho Eunae , Lee Bora , Lee Choong-Ki , Han Seungwu , Jeon Sang Ho , Park Bae Ho , Kim Yong-Sung
Published: June 2008

We perform first-principles calculations on metal-HfO2 interfaces in the presence of oxygen vacancies. Pt, Al, Ti, and Ag are considered as electrodes. It is found that oxygen vacancies are strongly attracted to the interface with binding energies of up to several eVs. In addition, the vacancy affinity of interfaces is proportional to the work function of metals, which is understood by the transition level of the vacancy and metal-Hf bonding. Interfacial segregation of vacancies significantly affects effective work functions of p metals. Our results are consistent with flatband shifts in p-type field effect transistors employing high-k dielectrics and metal gates.
Epitaxial MgO as an alternative gate dielectric for SiC transistor applications
Authors: Posadas A. , Walker F. J. , Ahn C. H. , Goodrich T. L. , Cai Z. , Ziemer K. S.
Published: June 2008

Power transistor applications require alternative gate dielectrics on SiC that can operate at high fields without breaking down, as well as provide a high quality interface in order to minimize mobility degradation due to interface roughness. We have grown epitaxial MgO (111) crystalline layers on 6H-SiC (0001) substrates and characterized their structural and electrical properties. Measurements of gate leakage, breakdown fields, and dielectric properties make epitaxial MgO a potential candidate gate dielectric for SiC-based transistors.
Characteristics and mechanism of conduction/set process in TiN∕ZnO∕Pt resistance switching random-access memories
Authors: Xu Nuo , Liu Lifeng , Sun Xiao , Liu Xiaoyan , Han Dedong , Wang Yi , Han Ruqi , Kang Jinfeng , Yu Bin
Published: June 2008

The characteristics and mechanism of conduction/set process in TiN∕ZnO∕Pt-based resistance random access memory devices with stable and reproducible nanosecond bipolar switching behavior were studied. The dependencies of memory behavior on cell area, operating temperature, and frequency indicate that the conduction mechanism in low-resistance states is due to electrons hopping through filament paths. We also identify that the set process is essentially equivalent to a soft dielectric breakdown associated with a polarization effect caused by the migration of space charges under a low electric field stress. The generation/recovery of oxygen vacancies and nonlattice oxygen ions play a critical role in resistance switching.
Anomalous magnetoresistance oscillations and enhanced superconductivity in single-crystal Pb nanobelts
Authors: Wang Jian , Ma Xu-Cun , Lu Li , Jin Ai-Zi , Gu Chang-Zhi , Xie X. C. , Jia Jin-Feng , Chen Xi , Xue Qi-Kun
Published: June 2008

Using atomically flat single-crystal Pb ultrathin films grown on Si(111) substrate by molecular beam epitaxy, we fabricated Pb nanobelts of 28 atomic monolayers thick, 285nm wide, and 10μm long by focus ion beam technique. The transport property is measured and the results are compared to the Pb films. We find that below the superconducting transition temperature TC, the resistance of the nanobelts exhibits clear and reproducible oscillations as a function of perpendicular magnetic field, which are not observed in the Pb films. In addition, TC enhancement was also observed in the nanobelts. The results suggest that the single-crystal Pb nanobelts prepared on Si semiconductor substrate offer a great opportunity for integrating superconducting circuits in a single Si chip.
Room-temperature ferromagnetism in the Co-doped Ba0.5Sr0.5TiO3 thin films
Authors: Luo L. B. , Zhao Y. G. , Tian H. F. , Yang J. J. , Zhang H. Y. , Li J. Q. , Ding J. J. , He B. , Wei S. Q. , Gao C.
Published: June 2008

The authors report the room-temperature ferromagnetism in the epitaxial thin films of 3% Co-doped Ba0.5Sr0.5TiO3 (CBSTO) grown by pulsed laser deposition. These films show the single phase character with Co dopants in the +2 state. More interestingly, ferromagnetic and ferroelectric transitions were observed at 570 and 150K, respectively. The CBSTO films also show the exchange bias effect manifested by the negative shift and training effect of the hysteresis loops at 5K. This work demonstrates that ferromagnetism can be induced in the ferroelectric materials, which is significant for shedding light on the mechanism of dopant induced ferromagnetism in insulators and applications.
Unusual strain dependence of tunability in highly (100)-oriented Mn-doped barium strontium stannate titanate thin films
Authors: Lu Shengbo , Xu Zhengkui
Published: June 2008

Highly (100)-oriented (Ba0.7Sr0.3)(Sn0.2Ti0.8−xMnx)O3 (Mn-BSSnT) (x=0%, 0.2%, 0.4%, 0.6%, and 1%) thin films were fabricated on (La0.7Sr0.3)CoO3∕LaAlO3 substrates by pulsed laser deposition. Both elastic residual strain and inhomogeneous strain were measured by x-ray diffraction techniques. The effect of strain on dielectric properties of the Mn-BSSnT thin films was investigated as a function of the Mn content. It was found that inhomogeneous strain has a greater effect on the tunability than the elastic residual strain does. The tunability decreases with increasing inhomogeneous strain and can be manipulated by changing Mn doping content, which is beneficial to real tunable device applications.
Growth of highly strain-relaxed Ge1−xSnx/virtual Ge by a Sn precipitation controlled compositionally step-graded method
Authors: Takeuchi Shotaro , Shimura Yosuke , Nakatsuka Osamu , Zaima Shigeaki , Ogawa Masaki , Sakai Akira
Published: June 2008

We have investigated Sn precipitation and strain relaxation behaviors in the growth of Ge1−xSnx layers on virtual Ge substrates (v-Ge) for strain engineering of Ge. By varying misfit strain at Ge1−xSnx∕v-Ge and Ge1−ySny∕Ge1−xSnx interfaces, we found that a critical misfit strain controls the onset of Sn precipitation at a given thickness of the Ge1−xSnx layer. A compositionally step-graded method, in which the critical misfit strain is taken into account, was applied to the growth of strain-relaxed Ge1−xSnx layers on v-Ge. Postdeposition annealing at each growth step led to lateral propagation of threading dislocations preexisting in the layer and originating from v-Ge, which resulted in high degree of strain relaxation. An epitaxial Ge layer was grown on the strain-relaxed Ge1−xSnx layer and an in-plane tensile strain of 0.68% was achieved.
Single-crystalline B12As2 on m-plane (11¯00) 15R-SiC
Authors: Chen Hui , Wang Guan , Dudley Michael , Xu Zhou , Edgar J. H. , Batten Tim , Kuball Martin , Zhang Lihua , Zhu Yimei
Published: June 2008

Single crystal, heteroepitaxial growth of icosahedral B12As2 (IBA, a boride semiconductor) on m-plane 15R-SiC is demonstrated. Previous studies of IBA on other substrates, i.e., (111)Si and (0001)6H-SiC, produced polycrystalline and twinned epilayers. In contrast, single-crystalline and untwinned IBA was achieved on m-plane 15R-SiC. Synchrotron white beam x-ray topography, Raman spectroscopy, and high resolution transmission electron microscopy confirm the high quality of the films. High quality growth is shown to be mediated by ordered nucleation of IBA on (474) substrate facets. This work demonstrates that m-plane 15R-SiC is a good substrate choice to grow high-quality untwinned IBA epilayers for future device applications.
Effect of gate bias sweep rate on the electronic properties of ZnO nanowire field-effect transistors under different environments
Authors: Maeng Jongsun , Jo Gunho , Kwon Soon-Shin , Song Sunghoon , Seo Jaeduck , Kang Seok-Ju , Kim Dong-Yu , Lee Takhee
Published: June 2008

We report the effects of gate bias sweep rate on the electronic characteristics of ZnO nanowire field-effect transistors (FETs) under different environments. As the device was swept at slower gate bias sweep rates, the current decreased and threshold voltage shifted to a positive gate bias direction. These phenomena are attributed to increased adsorption of oxygen on the nanowire surface by the longer gate biasing time. Adsorbed oxygens capture electrons and cause a surface depletion in the nanowire channel. Different electrical trends were observed for ZnO nanowire FETs under different oxygen environments of ambient air, N2, and passivation.
Ar gas discharge lamp with heated LiF window: A monochromatized light source for photoemission
Authors: Budke M. , Donath M.
Published: June 2008

We present a simple, inexpensive, and highly effective method for monochromatizing the vacuum ultraviolet light emitted from an Ar gas discharge for use, e.g., in photoemission experiments. By using a slightly heated window of LiF acting as low-pass filter, the emission spectrum of the Ar gas discharge is reduced to the Ar line at 11.62eV (106.7nm). The performance of the low-pass filter is demonstrated by photoemission measurements on Cu(111). Furthermore, we compare our light source with an unmonochromatized He gas discharge, which represents the most widely used laboratory photon source in photoemission.
Angular emission and self-absorption studies of a tin laser produced plasma extreme ultraviolet source between 10 and 18nm
Authors: Morris O. , O’Reilly F. , Dunne P. , Hayden P.
Published: June 2008

Extreme ultraviolet spectra from a tin laser produced plasma have been recorded over a range of angles between 20° and 90° from the target normal. Absolute intensity measurements are presented of both the 2% band centered on 13.5nm and the total radiation emitted by the plasma between 10 and 18nm. The in-band intensity is seen to be relatively constant out to an angle of 60° from the target normal, beyond which it drops off quite steeply. The spectra at wavelengths greater than 13.5nm are strongly influenced by self-absorption by ions ranging from 6+ to 10+.
Are the cost-benefits of grazing perennial ryegrass cultivars related to preference?
Authors: Bryant R. H. , Nicol A. M. , Edwards G. R.
Published: June 2008

Housed sheep (n = 6) were offered pairs of turves of 10 cultivars of perennial ryegrass extracted from pure sward plots over three 12-day experiments. Bite rate, bite mass and DM intake from each turf were recorded and preference was determined as the proportion of total DM removed. The ‘force to break leaves’ (FTB) and the metabolisable energy content were also measured and the marginal energy return (MER) of grazing each cultivar was calculated. Cultivars differed in preference (P < 0.01) and FTB (P < 0.05) in each experiment but MER only tended towards significance (P < 0.10) in the first experiment. There was no direct relationship between MER and preference. In one experiment sheep showed a preference for cultivars with lower FTB.
Smart Foods from the pastoral sector - implications for meat and milk producers
Authors: Bermingham E. N. , Roy N. C. , Anderson R. C. , Barnett M. P. G. , Knowles S. O. , McNabb W. C.
Published: June 2008

Smart Foods, or foods with functions that confer health benefits, are the future of the food and nutrition sectors. Pastoral products such as milk and meat are easily manipulated to improve the health benefits of these products. Therefore, there is the potential for farmers to add value to their current products. Additionally, the identification of key nutrients for health and the prevention of disease using nutrigenomic and nutritional epigenetic approaches may identify new ways to manipulate milk and meat products. However, consumer perceptions of product efficacy and the marketing of foods with health claims will be drivers behind the uptake of Smart Foods in the future.
Strategic use of sheep coats can improve your economic return
Authors: Hatcher S. , Atkins K. D. , Thornberry K. J.
Published: June 2008

Merino wethers from a mixed bloodline flock in western New South Wales were coated for varying periods of time after shearing between August 1999 and August 2000. The coated and a similar number of uncoated control wethers from each of nine bloodlines (three fine and six superfine) were grazed together as part of a larger mob. Dyebands were placed in the fleeces of each wether before fitting of the coats and were removed before shearing when a midside sample was taken and several subjective assessments and objective measurements were made of each fleece. It was concluded that coating sheep for 6 months after shearing is as effective in improving the quality of the Merino fleece as coating for the entire 12 month period between annual shearings. Strategic coating of sheep after shearing is a viable option for wool producers to both reduce some of the management implications of coating and extend the useful life of sheep coats. Importantly, the magnitude of the net financial gain will vary according to the prevailing micron premium and premiums and discounts applied to style and vegetable matter. A software tool is described that allows producers to identify the potential financial gain in any market scenario.
Validating the benefits of a medium voltage electrical stimulation unit at an abattoir in Western Australia
Authors: Jacob R. H. , Pearce K. L. , Smith N.
Published: June 2008

Two experiments were done following installation of a new generation medium voltage electrical stimulation unit at a commercial lamb abattoir in Western Australia. The first experiment was designed to optimise settings in relation to rate of pH decline post mortem. The second experiment was designed to investigate the eating quality and visual appearance effects of the optimal setting. In the first experiment, nine different settings were compared with a control using 60 lamb carcasses from each of 10 different consignments. The rate of pH × temperature decline was optimal with a pulse width of 2.5 ms and a current of 1.2 A.
In the second experiment, 80 lamb carcasses consisting of four carcasses from each of 20 consignments were examined for various eating quality parameters including sarcomere length, shear force, bloom colour and colour stability. Two of the lambs from each consignment were stimulated and two were not stimulated. Stimulation improved compliance with the Sheep Meat Eating Quality (SMEQ) pH × temperature ‘window’ for domestic and frozen product but not for long ship product. Colour was improved by electrical stimulation without changing colour stability. There was a small effect on sarcomere length and no effect of stimulation on shear force measured at day 1 and day 10 after slaughter.
Improving calf survival and performance by supplementation in Bali cattle
Authors: Jelantik I. G. N. , Mullik M. L. , Leo-Penu C. , Jeremias J. , Copland R.
Published: June 2008

An on-farm experiment was conducted in several villages in the district of Kupang, East Nusa Tenggara Province (NTT), Indonesia from June to October 2007. The experiment investigated the efficacy of a supplementation strategy to improve calf survival and performance during the dry season. A total of 258 Bali (Banteng, Bos javanicus) cow–calf pairs were used in the experiment. Calves from the 190 cow–calf pairs in the treatment groups were allocated grass hay + concentrate supplementation as follows: 1% (n = 98), 2% (n = 56) and 3% (n = 42) of calf bodyweight. There were 62 cow–calf pairs in the unsupplemented control group. The supplement consisted of grass hay and concentrate (rice bran, cornmeal, leucaena leaf and fish meal) containing 18% crude protein. The supplement was introduced to calves in the morning while confined to calf pens when the dams were grazing. Calves were reunited with the cows during the night. Parameters measured were calf mortality, calf and cow daily gain, and milk production. Supplementation tended to reduce calf mortality (P = 0.094) from 6.4% in control to 0% in calves receiving 2% and 3% supplement. Levels of supplementation significantly (P < 0.001) improved calf daily weight gain. Bodyweight changes and milk production of cows were unaffected by calf supplementation. It can be concluded that supplementation at 2% calf bodyweight reduces calf mortality and improves calf weight gain.
Intramuscular fat levels in sheep muscle during growth
Authors: McPhee M. J. , Hopkins D. L. , Pethick D. W.
Published: June 2008

A 5 × 4 factorial experiment was designed in which lambs representing five genotypes were slaughtered at four ages (110, 236, 412 and 662 days of age). The genotypes represented were Poll Dorsetgrowth × Border Leicester Merino, Poll Dorsetgrowth × Merino, Poll Dorsetmuscling × Merino, Merino × Merino and Border Leicester × Merino. Both sexes (ewes and wethers) were represented for each genotype and slaughter age combination. In total, 595 animals were slaughtered and the carcass composition and intramuscular fat were measured. Carcass composition [fat, ash and protein (lean)] was determined by dual energy X-ray absorptiometry, with the intramuscular fat percentage determined using near-infrared spectroscopy following removal and weighing of the entire longissimus thoracis et lumborum (LL) muscle. Analysis revealed that the proportion of intramusular fat in the loin relative to total carcass fat decreases as animals mature, thus indicating that intramusular fat deposition occurs early in the maturation of sheep. Furthermore, as animals became heavier and older the accretion rate of intramuscular fat in the LL muscle slowed down. Both genotype (P < 0.05) and sex (P < 0.001) were found to impact on this pattern, with Border Leicester × Merino animals exhibiting the largest increase in intramuscular fat proportion in the LL muscle (4.92 and 5.50% at 22 months of age for ewes and wethers, respectively). The Poll Dorsetgrowth × Border Leicester Merino animals were found to have the greatest absolute levels of intramuscular fat in the whole LL muscle (80.95 and 97.60 g at maturity for ewes and wethers, respectively). The amount of intramuscular fat significantly increased as the sheep became older and fatter; however, these differences were quantitatively small. As such, finishing prime lambs to high levels of total carcass fatness would have little effect on any eating quality benefits associated with increased intramuscular fat proportion.
Characterization of the pre-force-generation state in the actomyosin cross-bridge cycle
Authors: Sun Mingxuan , Rose Michael B. , Ananthanarayanan Shobana K. , Jacobs Donald J. , Yengo Christopher M.
Published: June 2008

Myosin is an actin-based motor protein that generates force by cycling between actin-attached (strong binding: ADP or rigor) and actin-detached (weak binding: ATP or ADP·P
i
) states during its ATPase cycle. However, it remains unclear what specific conformational changes in the actin binding site take place on binding to actin, and how these structural changes lead to product release and the production of force and motion. We studied the dynamics of the actin binding region of myosin V by using fluorescence resonance energy transfer (FRET) to monitor conformational changes in the upper-50-kDa domain of the actin binding cleft in the weak and strong actin binding states. Steady-state and lifetime data monitoring the FRET signal suggest that the cleft is in a more open conformation in the weak actin binding states. Transient kinetic experiments suggest that a rapid conformational change occurs, which is consistent with cleft closure before actin-activated phosphate release. Our results have identified a pre-force-generation actomyosin ADP·P
i
state, and suggest force generation may occur from a state not yet seen by crystallography in which the actin binding cleft and the nucleotide binding pocket are closed. Computational modeling uncovers dramatic changes in the rigidity of the upper-50-kDa domain in different nucleotide states, which suggests that the intrinsic flexibility of this domain allows myosin motors to accomplish simultaneous tight nucleotide binding (closed nucleotide binding pocket) and high-affinity actin binding (closed actin binding cleft).