Wire Direction Research Articles

Two-dimensional multiwire gas proportional detector for X-ray photon correlation spectroscopy of condensed matter

Details of a two-dimensional (2-D) multiwire gas proportional detector for X-ray photon correlation spectroscopy (XPCS) of condensed matter are described. The characteristics of the gas proportional detector at 8 keV, 0.3 pC anode charge, and 3 bar (absolute) of Xe/10%CO 2 are as follows: 8.5×10 −7 counts/s (100×100 μm 2) dark count rate, ∼μs time resolution, ∼48 and 73 μm position resolution (FWHM) along and across the anode wire direction, respectively, and ∼80% quantum efficiency. The effects of incident photon energy, anode charge (i.e., gain), gas drift depth, and gas pressure on position resolution are discussed. Static and dynamic speckle patterns, measured from disordered aerogel and polystyrene/polybutadiene blends by a partially coherent synchrotron X-ray source, demonstrate that a 2-D multiwire gas proportional detector is very suitable for the dynamic study of condensed matter with relaxation times in the order of μs to 10 3 s and atomic length scale.

Ultrafast carrier capture dynamics in InGaAs∕GaAs quantum wires

We use time-resolved terahertz-pulse spectroscopy to study the ultrafast carrier dynamics in InGaAs∕GaAs (311)A quantum wires. Anisotropy in the photoconductive dynamics is observed when aligning the terahertz probe polarization parallel versus perpendicular to the wire direction. The origin of this anisotropy is the carrier capture into localized quantum-wire states from delocalized wetting layer or barrier regions over time scales from 6to30ps. The capture efficiency is found to be strongly temperature dependent, with thermal emission dominating above 125K, while state-filling effects within the wires influence the capture rate below 125K. Transient spectroscopy reveals a Drude-like carrier conductivity.

Shielding Properties of a Wire-Medium Screen

The shielding performance of a planar metamaterial wire-medium (WM) screen under plane-wave illumination is studied. The screen consists of a finite number of periodic layers of thin conducting cylinders embedded in a dielectric matrix; in the low-frequency limit and for waves with the electric field polarized along the wire direction, such a screen can be modeled as a homogeneous slab with a plasma-like dispersive permittivity. In particular, well below the plasma frequency, the effective relative permittivity is negative and very large in absolute value, giving rise to high values of the shielding effectiveness. A comparison with a conventional planar metal screen is reported, showing how the proposed structure can be designed to be advantageous in terms of low density and weight saving. In order to be effective against arbitrarily polarized waves, the original structure is modified, adding a second WM screen with wires orthogonally oriented with respect to the first one. Numerical results are provided that illustrate the validity of the homogenized model in predicting field levels both near to and far from the screen and show the shielding performance attainable with the proposed metamaterial screen in both single- and double-layer configurations at normal incidence.

Highly anisotropic and electric field tunable Zeeman splittings in Mn-doped CdS nanowires

The electronic structure, Zeeman splitting, and $g$ factor of Mn-doped CdS nanowires are studied using the $k∙p$ method and the mean field model. It is found that the Zeeman splittings of the hole ground states can be highly anisotropic, and so can their $g$ factors. The hole ground states vary a lot with the radius. For thin wire, ${g}_{z}$ ($g$ factor when $B$ is along the $z$ direction or the wire direction) is a little smaller than ${g}_{x}$. For thick wire, ${g}_{z}$ is mcuh larger than ${g}_{x}$ at small magnetic field, and the anisotropic factor ${g}_{z}∕{g}_{x}$ decreases as $B$ increases. A small transverse electric field can change the Zeeman splitting dramatically, so tune the ${g}_{x}$ from nearly 0 to 70, in thick wire. The anisotropic factor decreases rapidly as the electric field increases. On the other hand, the Zeeman splittings of the electron ground states are always isotropic.

Measurement of Residual Stress in Thin-Sized Steel Wires by Using Focused Ion Beam and Digital Image Correlation Method

The residual stress in axial direction of the steel wires has been measured by using a method based on the combination of the focused ion beam (FIB) milling and digital image correlation (DIC) program. The residual stress is calculated from the measured displacement field before and after the introduction of a slot along the steel wires. The displacement is obtained by the digital correlation analysis of high-resolution scanning electron micrographs, while the slot is introduced by FIB milling with low energy beam. The experimental procedures are described and the feasibilities are demonstrated in steel wires fabricated with different conditions.

Quantum confinement effects on the spin splitting and polarization of quasi-1D holes

We study spin splitting and polarization of hole subband edges in nanowires with cylindrical and square cross-section in the presence of a magnetic field applied along the wire direction. A general feature of the interplay between quantum confinement and the strong spin–orbit coupling in the valence band is that the g-factors of the hole–wire bound states fluctuate strongly as a function of level index. In addition, they are suppressed in comparison to g-factors found in higher-dimensional systems. We analyze the hole–spin properties of the wire levels in terms of invariants of the spin- 3 2 density matrix and discuss effects of confinement and geometry on the hole–spin polarization and its correlation to the g-factor values.

Electronic structure of paramagnetic In1-xMnx As nanowires

The electronic structure, spin splitting energies, and g factors of paramagnetic In1-xMnxAs nanowires under magnetic and electric fields are investigated theoretically including the sp-d exchange interaction between the carriers and the magnetic ion. We find that the effective g factor changes dramatically with the magnetic field. The spin splitting due to the sp-d exchange interaction counteracts the Zeeman spin splitting. The effective g factor can be tuned to zero by the external magnetic field. There is also spin splitting under an electric field due to the Rashba spin-orbit coupling which is a relativistic effect. The spin-degenerated bands split at nonzero kz (kz is the wave vector in the wire direction), and the spin-splitting bands cross at kz = 0, whose kz-positive part and negative part are symmetrical. A proper magnetic field makes the kz-positive part and negative part of the bands asymmetrical, and the bands cross at nonzero kz. In the absence of magnetic field, the electron Rashba coefficient increases almost linearly with the electric field, while the hole Rashba coefficient increases at first and then decreases as the electric field increases. The hole Rashba coefficient can be tuned to zero by the electric field.

집속 이온빔과 디지털 화상 관련법을 이용한 고 탄소 미세 강선의 잔류 응력 측정

The residual stress in axial direction of the steel wires has been measured by using a method based on the combination of the focused ion beam(FIB) milling and digital image correlation(DIC) program. The residual stress is calculated from the measured displacement field before and after the introduction of a slot along the steel wires. The displacement is obtained by the digital correlation analysis of high-resolution scanning electron micrographs, while the slot is introduced by FIB milling with low energy beam. The experimental procedures are described and the feasibilities are demonstrated in steel wires fabricated with different conditions. It reveals that the tensile residual stress is formed in all steel wires and this is strongly influenced by the fabrication conditions.

Electron transport for a laser-irradiated quantum channel with Rashba spin–orbit coupling

We investigate theoretically the electron transport for a two-level quantum channel (wire) with Rashba spin-orbit coupling under the irradiation of a longitudinally-polarized external laser field at low temperatures. Using the method of equation of motion for Keldysh nonequilibrium Green function, we examine the time-averaged spin polarized conductance for the system with photon polarization parallel to the wire direction. By analytical analysis and a few numerical examples, the interplay effects of the external laser field and the Rashba spin–orbit coupling on the spin-polarized conductance for the system are demonstrated and discussed. It is found that the longitudinally-polarized laser field can adjust the spin polarization rate and produce some photon sideband resonances of the conductance for the system.

Hole Rashba effect and g-factor in InP nanowires

The hole Rashba effect and g-factor in InP nanowires in the presence of electric and magnetic fields which bring spin splitting are investigated theoretically in the framework of eight-band effective-mass envelop function theory, by expanding the lateral wave function in Bessel functions. It is well known that the electron Rashba coefficient increases nearly linearly with the electric field. As the Rashba spin splitting is zero at zero kz (the wave vector along the wire direction), the electron g-factor at kz = 0 changes little with the electric field. While we find that as the electric field increases, the hole Rashba coefficient increases at first, then decreases. It is noticed that the hole Rashba coefficient is zero at a critical electric field. The hole g-factor at kz = 0 changes obviously with the electric field.

Growth of ZnO Submicron Single-Crystalline Platelets, Wires, and Rods by Ultrasonic Spray Pyrolysis

Submicron single crystals of ZnO were grown by spray pyrolysis: the mist of an aqueous solution was generated by ultrasonic agitation and then pyrolyzed on a heated glass substrate. Hexagonal platelets of ZnO 10–90 nm thick were obtained when ammonium acetate was incorporated into the precursor solution of zinc acetate. Single-crystalline wires and rods, which were 50–150 and 300–4000 nm thick respectively, were obtained when indium nitrate was co-incorporated into the solution as a metal catalyst. The crystallographic direction of wires and rods was parallel to one of the [0001], [1010], or [1120] axis of wurtzite. As substrate temperature increased, the aspect ratio of the crystal thus tended to decrease. Structural and compositional analyses of these crystals were performed by scanning electron microscopy, scanning ion microscopy, transmission electron microscopy and electron diffraction, X-ray diffraction, X-ray photoelectron spectrocopy, and energy dispersive X-ray spectroscopy.

Impurity‐related optical properties in rectangular‐transverse section GaAs–Ga1–xAlxAs quantum well wires: Hydrostatic pressure and electric field effects

AbstractUsing a variational procedure within the effective mass approximation, we have calculated the influence of an applied electric field and hydrostatic pressure on the shallow‐impurity‐related optical properties in a rectangular‐transverse section GaAs–Ga1–x Alx As quantum well wire. The electric field is applied in the plane of the transverse section of the wire and different angular directions have been considered. The results presented are for the impurity binding energy, its corresponding density of impurity states, and impurity‐related transition energy and polarizability. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Study on the Wear of Diamond Beads in Wire Sawing

Diamond wire sawing has been used for many applications in stone industries and civil engineering several decades ago. The wear of bead is a major factor that affects wire-sawing performance in machining process. In this paper, seven diamond wires with different matrix system and different structures are taken from the factory. The diameters in the front, middle and end of bead along the moving direction of diamond wire, are measured respectively. The wear of diamond grits is also observed using a digital video microscope system. It is show that the wear of bead varies along the moving direction of diamond wire. The wear in the front of bead is greater than the others. The diameter gaps are associated with the type of matrix and the wear of diamond grits. The diameter gaps keep constant in the smooth sawing process.

Synthesis and Characteristics of Fe Nanowires

Arrays of 60-nm-diameter pores are synthesized by the electrochemical anodization of an aluminum substrate. Fe is electrodeposited in the pores to obtain the nanowire arrays. X-ray diffraction patterns and energy dispersive X-ray spectroscopy (EDS) show that the deposited material is pure iron. The Fe nanowire arrays possess a body-centered-cubic structure, and the wire direction of the nanowire arrays is orientated along the [110] direction. In the present study, we report the preferred [110] orientation along Fe nanowires with a diameter of 60 nm with values of parallel and perpendicular remanent magnetization of 0.4 and 4 memu, respectively.

Erfolgs- und Komplikationsrate der CT-gesteuerten Markierung pulmonaler Rundherde mittels Spirale vor videoassistierter thorakoskopischer chirurgischer Resektion (VATS)

To assess the success and complication rate of the CT-guided marking of pulmonary nodules for video-assisted thoracoscopic surgery (VATS). Pulmonary nodules (mean diameter 9 +/- 5 mm, mean pleural distance 7 +/- 5 mm) were marked with a coil wire in 30 patients (20 males, mean age 57.6 +/- 15.5 years, 22 patients with a history of malignancy). The intended coil-nodule distance was < or = 10 mm. 81 % of nodules were not visible by thoracoscopy. The technical success rate of CT-guided marking was 86.7 %. The projected nodule-coil distance was achieved in 90 % of cases. The procedure had to be changed from thoracoscopy to thoracotomy in 4 patients due to coil wire marking problems: 2 x coil displacement, 1 x coil-nodule distance > 10 mm, unfavorable direction of wire. Histology was determined in all patients (70 % malignant, 30 % benign). Complications requiring therapy were not observed. The CT-guided marking of pulmonary nodules is a precondition for VATS if the nodule does not involve the visceral pleura in the majority of cases. The success rate is high with a low complication rate.

Inverse dielectric function of a lateral quantum wire superlattice parallel to the interface of a plasma-like semiconductor

The dynamic, nonlocal, and spatially inhomogeneous polarizability and dielectric function are discussed in this paper for a Coulomb-coupled system of a periodic lateral superlattice array of one-dimensional quantum wire plasmas in the vicinity of a semi-infinite bulk plasma. The space-time matrix inverse of the dielectric function, i.e., the dynamic, nonlocal, inhomogeneous screening function of this system, is determined analytically here in closed form solving a random-phase-approximation type integral equation in position representation. We treat both cases wherein the lateral quantum wire superlattice is outside the semi-infinite plasma as well as inside. We also determine the exact coupled plasmon dispersion relation for the combined system for both the ``outside'' and ``inside'' cases: in this, we examine the band and gap structure of the spectrum due to periodicity of the quantum wire superlattice in the first Brillouin zone as a function of reciprocal-lattice wave number $p$, and also as a function of wave vector ${q}_{x}$ along the wire direction of full translational invariance. Furthermore, we analyze the spectrum of the combined system as a function of the period of the superlattice, showing that the detailed variation of the band-structure spectrum and gaps reflects on the period of the superlattice, opening the possibility of using surface plasmon resonance as a mechanism for optical sensing of nanostructure geometry. We also determine the dependence of the spectrum on distance of the superlattice from the bounding surface of the semi-infinite plasma, for both outside and inside cases. In the outside case, we show that at large distances the surface plasmon decouples from the superlattice plasmon band, while for short distances the two are fully coupled. For the inside case, they are similarly fully coupled for short distances, but for large distances, the surface plasmon decouples while the wire-superlattice plasmon band couples to the bulk plasmon deep in the semi-infinite medium.

Dynamic Intradigital External Fixation for Proximal Interphalangeal Joint Fracture Dislocations

Dynamic Intradigital External Fixation for Proximal Interphalangeal Joint Fracture Dislocations

Hydrostatic pressure and electric-field effects on the shallow donor impurity states in GaAs-Ga0.7Al0.3As quantum-well wires

Using a variational procedure within the effective-mass approximation, we have made a theoretical study of the effects of hydrostatic pressure and applied electric fields on the binding energy of a shallow-donor impurity in square-transversal section GaAs-Ga0.7Al0.3As quantum-well wires. The electric field is applied in a plane of the transversal section of the wire and many angular directions are considered. The hydrostatic pressure has been considered both in the direct and indirect gap regime for the Ga0.7Al0.3As material. For the potential barrier that defines the wire region, we consider an x-dependent finite and y-dependent infinite model. The results we present are for the impurity binding energy and considering different values of the wire dimensions, hydrostatic pressure, applied electric field, and the impurity position in the transversal section of the wire.

Rashba spin-orbit coupling in InSb nanowires under transverse electric field

We investigate the Rashba spin-orbit coupling brought by transverse electric field in InSb nanowires. In small ${k}_{z}$ (${k}_{z}$ is the wave vector along the wire direction) range, the Rashba spin-orbit splitting energy has a linear relationship with ${k}_{z}$, so we can define a Rashba coefficient similarly to the quantum well case. We deduce some empirical formulas of the spin-orbit splitting energy and Rashba coefficient, and compare them with the effective-mass calculating results. It is interesting to find that the Rashba spin-orbit splitting energy decreases as ${k}_{z}$ increases when ${k}_{z}$ is large due to the ${k}_{z}$-quadratic term in the band energy. The Rashba coefficient increases with increasing electric field, and shows a saturating trend when the electric field is large. As the radius increases, the Rashba coefficient increases at first, then decreases. The effects of magnetic fields along different directions are discussed. The case where the magnetic field is along the wire direction or the electric field direction are similar. The spin state in an energy band changes smoothly as ${k}_{z}$ changes. The case where the magnetic field is perpendicular to the wire direction and the electric field direction is quite different from the above two cases, the ${k}_{z}$-positive and negative parts of the energy bands are not symmetrical, and the energy bands with different spins cross at a ${k}_{z}$-nonzero point, where the spin splitting energy and the effective $g$ factor are zero.

Electronic structure and g factors of narrow-gap zinc-blende nanowires and nanorods

The Hamiltonian in the framework of eight-band effective-mass approximation of the zinc-blende nanowires and nanorods in the presence of external homogeneous magnetic field is given in the cylindrical coordinate. The electronic structure, optical properties, magnetic energy levels, and g factors of the nanowires and nanorods are calculated. It is found that the electron states consist of many hole-state components, due to the coupling of the conduction band and valence band. For the normal bands which are monotone functions of |kz|, long nanorods can be modeled by the nanowires, the energy levels of the nanorods approximately equal the values of the energy band E(kz) of the nanowires with the same radius at a special kz, where kz is the wave vector in the wire direction. Due to the coupling of the states, some of the hole energy bands of the nanowires have their highest points at kz≠0. Especially, the highest hole state of the InSb nanowires is not at the kz=0 point. It is an indirect band gap. For these abnormal bands, nanorods can not be modeled by the nanowires. The energy levels of the nanorods show an interesting plait-like pattern. The linear polarization factor is zero, when the aspect ratio L/2R is smaller than 1, and increases as the length increases. The gz and gx factors as functions of the kz, radius R and length L are calculated for the wires and rods, respectively. For the wires, the gz of the electron ground state increases, and the gz of the hole ground state decreases first, then increases with the kz increasing. For the rods, the gz and gx of the electron ground state decrease as the R or the L increases. The gx of the hole ground state decreases, the gz of the hole ground state increases with the L increasing. The variation of the gz of the wires with the kz is in agreement with the variation of the gz of the rods with the L.