Planar Wires Research Articles

Vortex Domain Wall Pinning Probability in Nanowires of Various Widths

We report the results of a micromagnetic simulation of vortex domain wall (VDW) dynamic pinning probability in 20-nm-thick planar permalloy wires with triangular notches and widths of 100, 200, and 300 nm. The notches have a fixed depth ratio of 30%, which is the depth divided by the wire width. Both the wire width and the applied field influenced the dynamic VDW pinning probability. The pinning probability decreased as the wire width increased. We observed a pinned domain wall (DW) structure around the notches and defined two types of pinning states, transverse DW pinning and VDW pinning. The 100-nm-wide wire had more transverse DW pinning–type events than did the 200- and 300-nm-wide wires. The 300-nm-wide wire had the lowest number of transverse DW pinning–type events. These results were caused by different wire widths having different DW energy densities and different pinning potential energy landscapes. When the applied field was larger than the Walker field, the wide wires easily led complex VDW motion.

Dependence of the three-phase transformers and reactors indicators from the steel filling of the circular and eight-plane contours of the rod of planar mixed magnetic wires

Purpose. The main elements of power transmission systems are transformers and reactors and the tasks of their improvement are especially relevant. The most common basis for these induction static devices are planar electromagnetic systems with rod magnetic circuits. Transformers and reactors with a capacity of over 16 kV A are made with circular generatrix circuits of the rods and winding coils. To ensure the filling of the sections of such rods with electrical steel with a coefficient of 0.851-0.931, 3-16 packets of various widths are placed in the halves of their cross sections, which significantly complicates the production of magnetic cores. Also, the circular configuration of the turns reduces the electrodynamic resistance of the windings. The aim of the work is to substantiate the advantages of replacing the traditional circular generatrix contours of active elements with octagonal ones. Methodology. A decrease in the main indicators (mass, cost, and loss) and an increase in the electrodynamic stability of transformers and reactors are achieved by using non-traditional designs with octagonal generatrix circuits of rods and winding coils, as well as a yoke with flat inner surfaces in lathing, butt and combined planar magnetic cores. An analysis of the effect of configuration changes and filling of the contours of the rods with steel on mass, cost and loss was performed by the method of target functions of an invariant design synthesis of electrical machines with optimized dimensionless parameters and relative controlled variables. Results. The extrema of the indicators of mass, cost and loss are calculated. It has been established that the use of octagonal generatrix circuits of cross-sections of rods and winding coils in an electromagnetic system leads to an improvement in mass-value indicators and a decrease in losses of three-phase transformers and reactors relative to analogues with circular generatrix circuits. The change in mass-value indicators depends on the fill factor of the circular contour of the rod with rectangular packages of electrical steel. Originality. Comparison of the values of dimensionless indicators gives an objective assessment of the advantages or disadvantages of the considered option of the electromagnetic system relative to the base analogue, regardless of the power, performance and cooling method. Practical value. Replacing in traditional systems of circular generatrix circuits with a jug with octagonal contours leads to an improvement in the extreme values of mass, cost, and loss indicators.

Negative refraction characteristics of a kind of concave metamaterial

This paper proposed a metamaterial with a high trough, high bandwidth, and high quality negative refraction band. It is composed of an axisymmetric concave sheet metal, an annular coil, and two parallel planar metal wires, and has passed the classical triangle verification. The influence of oblique incidence on the performance of the device was analyzed, and the relationship between plasma frequency and cell size was studied. By using an ingenious test scheme, the free space measurement of electromagnetic parameters was completed.

A Novel Three-Dimensional Electromagnetic Digital Actuator With 12 Discrete Positions

This paper presents a three-dimensional (3-D) digital electromagnetic actuator able to reach 12 discrete positions distributed in a 3-D space. The mobile part of this actuator includes a cuboid permanent magnet fixed in a hexagonal casing. The mobile part is able to reach six discrete positions in xy -plane at level z $_1$ and the remaining six discrete positions at level z $_2$ . The switching of the mobile part in xy -plane is achieved by injecting currents in the fixed planar wires situated beneath it. The actuator design integrates a coil to switch the mobile part between two predefined levels in z -axis. To maintain the mobile part at a discrete position without energy consumption, six fixed cylindrical permanent magnets are placed around the mobile part. To design the actuator, a model has been developed and is presented in this paper. Rapid prototyping approach (laser cutting) is used to fabricate the actuator prototype. The maximum and the minimum strokes in xy -plane are between 0.5 to 1.0 mm while along z -axis the actuator is able to perform a stroke of 1.0 mm. Experiments have been conducted on the prototype to validate the proposed design and the 3-D actuation. The performance characterization has been conduced and the experimental and the simulated results have been compared.

Comment on “Magnetic field calculation for arbitrarily shaped planar wires” [Am. J. Phys. 68(3), 254–258 (2000)

Comment on “Magnetic field calculation for arbitrarily shaped planar wires” [Am. J. Phys. <b>68</b>(3), 254–258 (2000)

High-Level Energy Estimation for Submicrometric TSV Arrays

The 3-D integration using through silicon vias (TSVs) is one of the most promising approaches to overcome the interconnect delay problem of current CMOS technologies. Nevertheless, the TSV energy consumption is not negligible due to the high capacitive coupling. This paper presents an abstract and yet accurate model to estimate the pattern-dependent energy consumption in arrays of TSVs; it is the first high-level model including the effects of the voltage-dependent metal–oxide–semiconductor (MOS) capacitances surrounding each TSV and a possible temporal misalignment between the input signals. We propose a regression method to estimate the dynamic size of the coupling capacitances as a function of the bit probabilities. Experimental results for real and synthetic data streams, a submicrometer 9-bit TSV array and a 65-nm technology show that the presented TSV energy model exhibits a maximum error of 5.53%, while the traditional high-level model shows errors of up to 79.77%. Furthermore, the new insights provided by our model reveal a possibility to easily boost the efficiency of existing low-power codes for TSV structures by over 10% without affecting the coding efficiency for the planar metal wires or the encoder complexity.

Planar Self-Assembly of Submicron and Nanoscale Wires and Grooves on III–V(110) Surfaces

Metallic Ga and In submicron and nanowires (NWs) tens of microns long naturally form via a self-propelled mechanism on the (110) surfaces of GaAs and InAs, respectively, during noncongruent sublimation in ultrahigh vacuum. Under stringent conditions, low-energy electron microscopy uncovers GaAs and InAs(110) surfaces on the brink of decomposition rapidly assemble planar wires of their cations in the ⟨110⟩ direction. For InP(110), wire formation is unfavorable due to a smooth decomposing front but can be assisted by Au nanoparticles (NPs), which sacrifice themselves to form rough pits via solid–liquid–vapor etching. The resulting self-assembled and AuNP-assisted NWs grow crystallographically in a self-sustainable manner, unless they are obstructed and consumed by stationary microdroplets, leaving emptied grooves. The findings reveal a hitherto hidden natural process on the surfaces of binary crystals capable of producing elementary submicron and nanoscale wires without extrinsic materials, paving the way ...

Inkjet‐printed 3D Hilbert‐curve fractal antennas for VHF band

AbstractTwo miniaturized wire antennas using a 3D space‐filling Hilbert‐curve (HC) fractal geometry were constructed on a Kodak photo paper using inkjet printing. The proposed antennas each had the 3D dimensions of an 8 cm3 box and operate at very high‐frequency band frequencies of 238 and 147 MHz. We wrapped 4‐ and 2‐mm‐thick planar wires around a 3D box made of photo paper using second‐ and third‐order HC space‐filling fractal designs. The electrical volumes of the proposed second‐order HC and third‐order HC fractal antennas were 0.004 λ0 × 0.004 λ0 × 0.004 λ0 and 0.002 λ0 × 0.002 λ0 × 0.002 λ0, respectively. The operation of the proposed antennas was verified using simulation and measurement results.

Dual-band quasi-zero refraction and negative refraction in coin-shaped metamaterial

This paper demonstrates a metamaterial capable of realizing a dual-band quasi-zero refractive index and a negative refractive index, which consists of a coin-shaped slice and two parallel planar wires. The zero refractive index is achieved over a very wide frequency range. The bandwidth of the first band of the quasi-zero index can reach up to 3 GHz, and the width of the second band exhibiting low loss is 0.4 GHz. Between these two bands, the negative refractive index band is 9.0–13.9 GHz. The corresponding formulas of electric plasma frequency and magnetic plasma frequency are established, and the theoretical results agree well with the simulated results. The proposed metamaterial may have potential applications in multiband or broadband devices.

Magnetic anisotropies in epitaxial Fe3O4/GaAs(100) patterned structures

Previous studies on epitaxial Fe3O4 rings in the context of spin-transfer torque effect have revealed complicated and undesirable domain structures, attributed to the intrinsic fourfold magnetocrystalline anisotropy in the ferrite. In this Letter, we report a viable solution to this problem, utilizing a 6-nm-thick epitaxial Fe3O4 thin film on GaAs(100), where the fourfold magnetocrystalline anisotropy is negligible. We demonstrate that in the Fe3O4 planar wires patterned from our thin film, such a unique magnetic anisotropy system has been preserved, and relatively simple magnetic domain configurations compared to those previous reports can be obtained.

Gold planar wire array radiation sources at university scale generators and their applications

Various configurations of planar wires arrays (PWA) made from wires in a broad range of atomic numbers up to 74 (W) have been extensively tested on Zebra generator at the University of Nevada, Reno. In this work, we present the results of our experiments with PWA made of the wires with an even higher atomic number, specifically 79 ( Au ). Two different configurations (single and double PWAs) are considered. The diagnostic set included: x-ray detectors, laser shadowgraphy, time-gated and time-integrated x-ray pinhole cameras, time-integrated spatially resolved and time-gated spatially integrated x-ray spectrometers, and a bolometer. The total x-ray yield was measured along and perpendicular to the load plane and reached the highest value measured on Zebra so far for the single PWA (perpendicular to the plane, 32 kJ). Theoretical tools included non-LTE kinetic and wire ablation dynamic models. The full set of data using aforementioned diagnostics is analyzed and specific implosion and radiative characteristics of Au PWAs. The application of gold PWAs in compact hohlraum configurations on Zebra is highlighted. VisRad (Prism Computational Sciences), a 3-D view factor code, is used to simulate the multi-dimensional radiation environment with a special emphasis on radiation temperature calculations and uniformity at the re-emission target surface.

Metal-coated silicon micropillars for freestanding 3D-electrode arrays in microchannels

This paper presents a fabrication process for arrays of high-aspect-ratio micropillar electrodes, which are freestanding 3D structures that feature metal sidewalls connected to passivated planar wires. Facing vertical electrodes are considered to be a key solution in microdevice technologies, as they are able to improve the efficiency and accuracy of electrical methods by generating homogeneous electric fields along the height of microfluidic channels. Despite the acknowledged advantages of using vertical microelectrodes, current microfabrication technologies do not allow the manufacture of such structures with the same resolution and versatility as planar electrodes. The present study focused on the fabrication of round and square-shaped silicon pillar arrays exposing metal on their sidewalls, which is decoupled from the substrate by means of a passivation layer. The pillars range in width from 10μm to 70μm, with gaps down to 10μm and a maximum aspect ratio of 5:1. Metal deposition and patterning were revealed to be the critical steps of the process. Deposition was achieved by sputtering, while patterning was performed by photolithography, and the photoresist was applied by spray-coating. The pattern was then transferred into the metal layer by means of dry etching. This new process can be adapted to any metal that is suitable for depositing by sputtering and patterning by dry etching. The presence of the metal layer on the vertical sidewalls was confirmed by SEM imaging combined with EDX analysis. The arrays were then characterized by electrical conductivity measurements and impedance spectroscopy.

Understanding Self-Aligned Planar Growth of InAs Nanowires

Semiconducting nanowires have attracted lots of attention because of their potential applications. Compared with free-standing nanowires, self-aligned planar nanowires grown epitaxially on the substrate have shown advantageous properties such as being twin defect free and ready for device fabrication, opening potentials for the large-scale device applications. Understanding of planar nanowire growth, which is essential for selective growth of planar vs free-standing wires, is still limited. In this paper, we reported different growth behaviors for self-aligned planar and free-standing InAs nanowires under identical growth conditions. We present a new model based on a revised Gibbs–Thomson equation for the planar nanowires. Using this model, we predicted and successfully confirmed through experiments that higher arsenic vapor partial pressure promoted free-standing InAs nanowire growth. A smaller critical diameter for planar nanowire growth was predicted and achieved experimentally. Successful control and understanding of planar and free-standing nanowire growth established in our work opens up the potential of large-scale integration of self-aligned nanowires for practical device applications.

Effect of Surface Oxidation on the Magnetization Reversal of Cobalt Planar Wires

The influence of the antiferromagnetic layer of cobalt oxide on the magnetization reversal of a submicron cobalt planar wire was studied using the magneto-transport measurements. For pure Cobalt (Co) planar wires of width less than 1.2 μm, length of 30 μm, and thickness of 30 nm, the shape anisotropy dominates the magnetic behavior revealing all characteristics of a single domain structure. With oxidation, there is a thin layer of CoO on top of the Co layer and the exchange coupling between the CoO (antiferromagnet) and Co (ferromagnetic) layers may suppress the shape anisotropy induced single domain structure and the typical switching behavior of magnetization reversal. The magnetic configuration and magnetization reversal are determined by the competition of unidirectional anisotropy and exchange coupling constant.

Magnetic-field instability of Majorana modes in multiband semiconductor wires

We investigate the occurrence of Majorana modes in semiconductor quantum wires in close proximity with a superconductor and when both, Rashba interaction and magnetic field, are present. We consider long, but finite, multiband wires (namely, planar wires with dimensions $L_x\gg L_y$). Our results demonstrate that interband mixing coming from Rashba spin orbit term hybridizes Majorana pairs originating from different transverse modes while simultaneously closing the effective gap. Consequently, multiple Majorana modes do not coexist in general. On the contrary, Majorana physics is robust provided that only one single transverse mode contributes with a Majorana pair. Finally, we analyse the robustness of Majorana physics with respect to magnetic orbital effects.

Finite size effects on transport coefficients for models of atomic wires coupled to phonons

We consider models of quasi-1-d, planar atomic wires consisting of several, laterally coupled rows of atoms, with mutually non-interacting electrons. This electronic wire system is coupled to phonons, corresponding, e.g., to some substrate. We aim at computing diffusion coefficients in dependence on the wire widths and the lateral coupling. To this end we firstly construct a numerically manageable linear collision term for the dynamics of the electronic occupation numbers by following a certain projection operator approach. By means of this collision term we set up a linear Boltzmann equation. A formula for extracting diffusion coefficients from such Boltzmann equations is given. We find in the regime of a few atomic rows and intermediate lateral coupling a significant and non-trivial dependence of the diffusion coefficient on both, the width and the lateral coupling. These results, in principle, suggest the possible applicability of such atomic wires as electronic devices, such as, e.g., switches.

Efficient Generation of Propagating Plasmons by Electron Beams

We report highly efficient generation of propagating plasmons by electron beams in planar films, planar dielectric cavities, metallic wires, and nanoparticle waveguides. Electron-induced plasmon excitation is investigated in (1) gold thin films, both free-standing or supported on a silica substrate, (2) gold-silica-gold planar cavities, (3) gold nanowires, and (4) gold nanoparticle arrays. We obtain excitation yields as high as 10(- 2) plasmons per incoming electron over the visible and near-infrared range. Symmetric and antisymmetric plasmon modes are found to be more easily excited in thick and thin films, respectively, and in particular leaky plasmons in supported films are shown to be excited with very large probability exceeding one plasmon per electron. Generation of guided plasmons in metallic particle arrays is also proved to be attainable by aiming the electron at one end of the waveguide. The temporal evolution and spectral distribution of excited plasmons are discussed as well. Our results provide full support for the application of electron bombardment to excite propagating plasmons with high efficiency, thus solving the standing problem of plasmon generation at designated locations.

Experimental observation of minigap stripes in periodically corrugated broad photonic wires

A multimodal one-dimensional photonic wire subject to a periodic corrugation of the boundary exhibits minigaps among its dispersion branches. For equidistant branches, these minigaps form marked stripes that occupy a substantial fraction of the dispersion diagram and deeply modulate the photon density of states. We experimentally observe these stripes in relatively broad planar photonic wires---$15--30\text{ }\ensuremath{\lambda}/n$ wide---whose lateral confinement is based on two-dimensional photonic-crystal lattices defined in a vertically confining InP heterostructure. The waveguides are tilted at an angle to collect the spontaneous emission of embedded quantum wells channeled into the modes corresponding to the dispersion branches. The minigap stripes manifest themselves as large intensity modulations in the spontaneous emission spectra in TE and TM polarizations. An analogy with the appearance of similar minigap stripes in the recently studied edge-corrugated graphene nanoribbons is pointed out.

Fabrication of one‐dimensional “trenched” GaN nanowires and their interconnections

AbstractIn this work, a new approach of nanowire fabrication utilizing selective growth of planar GaN wires embedded into the insulating matrix is reported. The selective growth has been released by means of a Six Ny mask and a metal‐organic chemical vapour deposition. The main advantage of the investigated fabrication process is a planar geometry of the wires allowing the use of conventional interconnection techniques such as optical lithography. Design, fabrication technology and interconnection geometry of some early examples are discussed. (© 2007 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Interface-Optical-Phonon Modes in Quasi-one-dimensionalWurtzite Rectangular Quantum Wires

By employing the dielectric continuum model and Loudon'suniaxial crystal model, the interface optical (IO) phonon modesin a freestanding quasi-one-dimensional (Q1D) wurtzite rectangularquantum wire are derived and analyzed. Numerical calculation on afreestanding wurtzite GaN quantum wire is performed. The resultsreveal that the dispersion frequencies of IO modes sensitivelydepend on the geometric structures of the Q1D wurtzite rectangularquantum wires, the free wave-number kz in z-direction and thedielectric constant of the nonpolar matrix. The degeneratingbehavior of the IO modes in Q1D wurtzite rectangular quantum wirehas been clearly observed in the case of small wave-number kz andlarge ratio of length to width of the rectangular crossing profile.The limited frequency behaviors of IO modes have been analyzed deeply,and detailed comparisons with those in wurtzite planar quantum wellsand cylindrical quantum wires are also done. The present theories canbe looked on as a generalization of that in isotropic rectangularquantum wires, and it can naturally reduce to the case of Q1D isotropicquantum wires once the anisotropy of the wurtzite material is ignored.