共查询到20条相似文献,搜索用时 31 毫秒
1.
Perpendicular structured nanowire arrays interaction field distributions (IFDs), as revealed from first-order reversal curves (FORC) diagrams, are related to the presence of the demagnetizing field in the system. Despite the similarity between the geometric properties of bit patterned media and mentioned nanowire arrays, FORC diagrams of these two types of systems are not similar essentially due to the different number of magnetic entities influencing the switch of an individual element. We show that one Preisach–Krasnosel'skii–Pokrovskii (PKP) symmetrical hysteron can be representative of an ideal infinite nanowire array when the field is applied along the wires. Starting from this observation, we present a very simple model based on PKP symmetrical hysterons that can be applied to real finite ferromagnetic nanowire arrays, and is able to describe a wide class of experimentally observed FORC distributions, revealing features due to size effects. We also present IFDs modeled for different geometric characteristics such as array size, interwire distance, and nanowire dimensions, and an identification procedure for the proposed model. 相似文献
2.
We demonstrate the importance of magnetostatic interactions in dense arrays of ferromagnetic nanowires. Beginning from a simple micromagnetic model, we have calculated the interaction field for saturated magnetization in the plane of the array (perpendicular to the axes of the wires) and normal to the plane, using a hybrid (numerical and analytical) strategy. The slope of interaction field versus wire length changes dramatically at the transition between a dipolar regime (at very small lengths) and a monopolar regime (for longer nanowires). We present the interaction fields and the applied fields at saturation for large nanowire arrays. These results are compared with experiment for electrodeposited arrays, and very good agreement is obtained. This shows that the high field behavior of such arrays is dominated by magnetostatic effects and that a nanowire array behaves like a double-sided distribution of magnetic monopoles. 相似文献
3.
Micromagnetic simulation on the dynamic susceptibility spectra of cobalt nanowires arrays: the effect of magnetostatic interaction
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
<正>Micromagnetic simulations have been performed to obtain the dynamic susceptibility spectra of 4×4 cobalt nanowire arrays with different spatial configurations and geometries.The susceptibility spectra of isolated wires have also been simulated for comparison purposes.It is found that the susceptibility spectrum of nanowire array bears a lot of similarities to that of an isolated wire,such as the occurrences of the edge mode and the bulk resonance mode. The simulation results also reveal that the susceptibility spectrum of nanowire array behaves like that of single isolated wire as the interwire distance grows to an extent,which is believed due to the decrease of magnetostatic interaction among nanowires,and can be further confirmed by the static magnetic hysteresis simulations.In comparison with single nanowire,magnetostatic interaction may increase or decrease the resonance frequencies of nanowire arrays assuming a certain interwire distance when the length of array increases.Our simulation results are also analysed by employing the Kittel equation and recent theoretical studies. 相似文献
4.
陷光结构的优化是增加硅薄膜太阳电池光吸收进而提高其效率的关键技术之一. 以硅纳米线阵列为代表的光子晶体微纳陷光结构具有突破传统陷光结构Yablonovith极限的巨大潜力. 通常硅纳米线阵列可以用作太阳电池的增透减反层、轴向p-n结、径向p-n结. 针对以上三种应用, 本文运用有限时域差分(FDTD)法系统研究了硅纳米线阵列在 300-1100 nm 波段的光学特性. 结果表明, 当硅纳米线作为太阳电池的减反层时, 周期P=300 nm, 高度H=1.5 μm, 填充率(FR)为0.282条件下时, 反射率最低为7.9%. 当硅纳米线作为轴向p-n结电池时, P=500 nm, H=1.5 μm, FR=0.55条件下纳米线阵列的吸收效率高达22.3%. 硅纳米线作为径向p-n结电池时, 其光吸收主要依靠纳米线, 硅纳米线P=300 nm, H=6 μm, FR= 0.349 条件下其吸收效率高达32.4%, 进一步提高其高度吸收效率变化不再明显. 此外, 本文还分析了非周期性硅纳米线阵列的光学性质, 与周期性硅纳米线阵列相比, 直径随机分布和位置随机分布的硅纳米线阵列都可以使吸收效率进一步提高, 相比于周期性硅纳米线阵列, 优化后直径随机分布的硅纳米线阵列吸收效率提高了39%, 吸收效率为27.8%. 本文运用FDTD法对硅纳米线阵列的光学特性进行设计与优化, 为硅纳米线阵列在太阳电池中的应用提供了理论支持. 相似文献
5.
Clotaire Chevalier-César Martine Capochichi-Gnambodoe Yamin Leprince-Wang 《Applied Physics A: Materials Science & Processing》2014,115(3):953-960
Well-controlled ZnO nanowire arrays have been synthesized using the hydrothermal method, a low temperature and low cost synthesis method. The process consists of two steps: the ZnO buffer layer deposition on the substrate by spin-coating and the growth of the ZnO nanowire array on the seed layer. We demonstrated that the microstructure and the morphology of the ZnO nanowire arrays can be significantly influenced by the main parameters of the hydrothermal method, such as pH value of the aqueous solution, growth time, and solution temperature during the ZnO nanowire growth. Scanning electron microscopy observations showed that the well oriented and homogeneous ZnO nanowire arrays can be obtained with the optimized synthesis parameters. Both x-ray diffraction spectra and high-resolution transmission electron microscopy (HRTEM) observations revealed a preferred orientation of ZnO nanowires toward the c-axis of the hexagonal Wurtzite structure, and HRTEM images also showed an excellent monocrystallinity of the as-grown ZnO nanowires. For a deposition temperature of 90 °C, two growth stages have been identified during the growth process with the rates of 10 and 3 nm/min, respectively, at the beginning and the end of the nanowire growth. The ZnO nanowires obtained with the optimized growth parameters owning a high aspect ratio about 20. We noticed that the starting temperature of seed layer can seriously influence the nanowire growth morphology; two possible growth mechanisms have been proposed for the seed layer dipped in the solution at room temperature and at a high temperature, respectively. 相似文献
6.
In this article, we describe the coating of silicon nanowire arrays with thin dielectric layers using Plasma Enhanced Chemical
Vapor Deposition (PECVD). The impact of deposition pressure, temperature, and nanowire array density on the silicon oxide
coating thickness uniformity was assessed using a detailed electron microscopy observations of the nanowire arrays. Deposition
rates were found to vary along the nanowire length as a function of the above process parameters, and ranged from 0 to 35 nm/min.
The coating thickness was found to be most uniform at higher pressures and temperatures, and high-density nanowire arrays
with smaller nanowire diameters and larger lengths led to the deposition of coating with a smaller thickness gradient along
the wire length. 相似文献
7.
8.
We numerically investigate the band structure and guided modes within arrays of metallic nanowires. We show that bandgaps appear for a range of array geometries and that these can be used to guide light in these structures. Values of attenuation as low as 1.7 dB/cm are predicted for arrays of silver wires at communications wavelengths. This is more than 100 times smaller than the attenuation of the surface plasmon polariton modes on a single silver nanowire. 相似文献
9.
10.
We report on experimental results which we conducted on manufactured microretarder arrays. The array consists of miniaturized retarder elements with different orientations of their fast axes. Diffractive phase retardation elements are chosen as microretarder elements since nanostructuring techniques such as electron beam lithography and successive reactive ion etching allow in principle an effortless way to arrange the microretarders as desired by the application. In this paper, we discuss the fabrication and the experimental results of manufactured retarder arrays. Furthermore, their use for potential applications in the fields of polarimetry is discussed. 相似文献
11.
Fabrication and magnetic property of binary Co-Ni nanowire array by alternating current electrodeposition 总被引:1,自引:0,他引:1
Ordered binary Co-Ni nanowire arrays with different components have successfully been fabricated by ac electrodeposition. The as-obtained nanowires exhibit a diameter of about 49.2 nm and aspect ratio of more than 30. A highly preferential orientation of the Co-Ni nanowires has been obtained by XRD. The magnetic properties of Co-Ni nanowire arrays determined by VSM are as the function of the Co-Ni components. The maximum value of coercivities perpendicular to the array is 2073 Oe. However, the magnetic properties of such nanowire arrays exhibited a bad thermal stability at the medium temperature of 200 °C. 相似文献
12.
A. Rahm M. Lorenz T. Nobis G. Zimmermann M. Grundmann B. Fuhrmann F. Syrowatka 《Applied Physics A: Materials Science & Processing》2007,88(1):31-34
We report on the high-pressure pulsed-laser deposition growth of periodic arrays of free-standing single zinc oxide nanowires
with uniform hexagonal arrangement and cross-section with thickness of less than 100 nm. In order to achieve the wire alignment,
we prepared an ordered array of catalytic gold seed particles by a nanosphere lithography mask transfer technique using monodisperse
spherical polystyrol nanoparticles. These templates were investigated by scanning electron microscopy and atomic force microscopy
prior to nanowire growth. X-ray diffraction revealed the epitaxial relationships between the nanostructures and the a-plane
sapphire substrate and excellent crystal quality. The optical properties of the ZnO nanowire arrays were measured by cathodoluminescence.
PACS 61.82.Rx; 81.05.-t; 81.05.Dz; 81.10.-h 相似文献
13.
Jianfeng Yuan W. Pei T. Hasagawa T. Washiya H. Saito S. Ishio Hirotaka Oshima Ken-ichi Itoh 《Journal of magnetism and magnetic materials》2008
The magnetic properties of self-assembly cobalt nanowire arrays formed in anodic porous alumina template were investigated by nanosize imaging method and macroscopic magnetic measurement. We have successfully made a wire-by-wire observation of magnetization reversal of a cobalt nanowire array using magnetic force microscopy with a home-made FePt tip. The nanowires in this medium have uniaxial anisotropy with easy axis along the wire due to the large aspect ratio of the wires (30 nm in diameter and 300 nm in length). Considering the nanowires as single-domain structures, we can obtain the average DC demagnetization curve from nanosize images by calculating the number of wires in each magnetized direction, and the results agreed well with the DC demagnetization curve measured by macroscopic measurement. The magnetostatic field between wires was evaluated by a new nanosize imaging method. Macroscopic measurement shows that reversible magnetization occurs in this medium. Nanosize images of the remanent and saturated states prove that the reversible magnetization processes mainly take place inside individual wires and reversed wires induced by magnetostatic field just give a little contribution to the reversible magnetization. 相似文献
14.
Feiyang Wu Logeeswaran VJ M. Saif Islam David A. Horsley Robert G. Walmsley Sagi Mathai Denny Houng Michael R. T. Tan Shih-Yuan Wang 《Applied Physics A: Materials Science & Processing》2009,95(4):1079-1088
In many computer and server communications copper cables and wires are currently being used for data transmission and interconnects.
However, due to significant shortcomings, such as long transmission time, high noise level, unstable electrical properties,
and high power consumption for cooling, researchers are increasingly turning their research interests toward alternatives,
such as fiber optic interconnects and free-space optical communication technologies. In this paper, we present design considerations
for an integrated receiver for high-speed free-space line-of-sight optical interconnects for distortion-free data transmission
in an environment with mechanical vibrations and air turbulences. The receiver consists of an array of high-speed photodiodes
for data communication and an array of quadrant photodiodes for real-time beam tracking in order to compensate for the beam
misalignment caused by vibrations in servers. Different configurations for spatially positioning the quadrant and data photodiodes
are discussed for 4×4 and 9×9 multielement optical detector arrays. We also introduce a new beam tracking device, termed the
strip quadrant photodiodes, in order to accurately track highly focused optical beams with very small beam diameter. 相似文献
15.
L. Clime F. Béron P. Ciureanu M. Ciureanu R.W. Cochrane A. Yelon 《Journal of magnetism and magnetic materials》2006
We present a phenomenological model for the interaction field in ferromagnetic nanowire arrays and use it to obtain the effective anisotropy field of individual nanowires, from the in-plane saturation field of the array. In contrast to other methods which may be used to estimate this parameter, the proposed strategy requires no knowledge of the saturation magnetization nor of the nanowire radius. Applied to three arrays of different compositions, this approach yields an equivalent anisotropy field of the individual nanowires approximately equal to Ms/2, indicating that its origin is the demagnetizing field of the wire. 相似文献
16.
Quasi-horizontal GaN nanowire array network has been grown on Au-film-coated MgO substrates via a sublimation sandwich technique. These GaN nanowire arrays principally grew along two directions which were perpendicular to each other and nearly parallel to the substrate, forming a regular network. The formation of the nanowire network was a hetero-epitaxial vapor-liquid-solid (VLS) process assisted by Au catalysts and was dependent on the substrates. Transmission electron microscopy revealed that the nanowires were single-crystalline wurtzite GaN. Raman scattering spectrum of the nanowire network presented some new features. 相似文献
17.
18.
JIAO XingJian WANG Xiao LI Xin CHEN HuiYuan WANG Gang LI JianBao LIN Hong 《中国科学:物理学 力学 天文学(英文版)》2014,57(5):892-897
Anatase titanium dioxide nanowire arrays were prepared by hydrothermally oxidizing titanium foils in aqueous alkali and transferred onto fluorinated tin oxide(FTO)glass for use as the photoanodes of front side illuminated dye-sensitized solar cells(DSCs).Electrochemical impedance spectroscopy(EIS)measurement was applied to compare the electron transport and recombination properties of DSCs using TiO2nanowire films and TiO2nanoparticle films as photoanodes.It was found that the nanowire array films possess smaller electron transport resistance(Rt)and larger electron diffusion length(Le)in the photoanodes,suggesting that the nanowire arrays can enhance the electron transport rate and have a potential to improve the charge collection efficiency of DSCs. 相似文献
19.
《Current Applied Physics》2015,15(1):34-37
We investigated the optical characteristics and expected photocurrent of 10-μm-thick Si solar cells with surface nanowire arrays. The diameter and filling ratio of the array influenced not only the optical absorption, but also the spatial distribution of the optical generation rate. Proper design of the nanowire array could locate the high optical field region far from the surface, avoiding serious carrier collection loss and raising the energy conversion efficiency. 相似文献
20.
Arrays of ordered Ag nanowires with different diameters in different areas embedded in one piece of anodic alumina membrane 总被引:1,自引:0,他引:1
Nanochannel arrays with the same nanochannel density but different nanochannel diameters in different areas in one piece of anodic alumina membrane had been created. SEM observations on one piece of this type of anodic alumina membrane show that the nanochannel diameters radially decrease from 80 nm to 60 nm and to 40 nm along the radial direction. Therefore, using this type of membrane as a template, ordered Ag nanowire arrays with the same nanowire density but with diameters decreasing radially were obtained by electrodeposition. SEM and TEM images taken of different areas of the Ag nanowire arrays show that we can control the growth of aligned Ag nanowires with different diameters in a single process at the same time. Using this type of template in combination with other fabrication techniques, nanometer-scale fibrils, rods, wires, and tubules of metal, semiconductors, carbon, and other materials with same density but different diameters in different areas can be fabricated. The simultaneous integration of ordered nanowire structures with different diameters embedded in a single anodic alumina membrane could be useful in nanodevice manufacture as well as electronics, optoelectronics and magnetics. PACS 81.05.Bx; 82.80.Fk; 85.30.Vw 相似文献