Nanochannels Of Anodic Alumina Membranes Research Articles

Crossover between axial and radial magnetic anisotropy in self-organized permalloy nanowires

Self-organized permalloy nanowire arrays embedded in hexagonally ordered nanochannels of anodic alumina membranes were produced by electrodeposition. The dimensions of the nanowires were tuned over a wide range by controlling the dimensions of the host alumina templates. Room temperature magnetic hysteresis revealed a considerable dependence of the magnetic anisotropy of the array on the nanowire dimensions. The magnetization direction of the nanowires was found to change from axial to longitudinal direction as both the diameter and length of the wire increased. The observed behavior was ascribed to the increase in magnetostatic coupling among nanowires, as confirmed by first-order reversal curve measurements. Theoretical calculations based on a simple magnetostatic model, which considers the dipolar interaction among the wires, estimated the critical dimensions of the nanowires at which the magnetic anisotropy changes from perpendicular to longitudinal direction.

Experimental and Theoretical Study of Enhanced Vapor Transport through Nanochannels of Anodic Alumina Membranes in a Capillary Condensation Regime

The pressure-driven flow of condensable and permanent gases was studied experimentally for anodic alumina membranes with channel diameters ranging from 20 to 90 nm depending on feed and permeate pressures. A substantial permeability rise for condensable gases was detected under capillary condensation conditions. A self-consistent theoretical model for mixed liquid–gas transport through the nanopore was suggested based on the obtained experimental results. The model was used for the evaluation of the pressure drop in a liquid defined by menisci curvatures and determination of the optimal conditions to enhance the membrane performance. The highest pressure difference in a liquid can be obtained by decreasing the entrance meniscus curvature with a simultaneous increase in the curvature of the evaporating meniscus. This case was realized in asymmetric membranes with multiple branching of channels into 5 nm nanocapillaries, resulting in up to 10× enhancement of isobutane permeability (up to 450 m3/(m2·bar·h)) ...

Synthesis and Magnetic Properties of FePt Fe3Pt Nanowire Arrays Embedded in Anodic Alumina Membranes

FePt Fe3Pt nanowire arrays embedded in the nanochannels of anodic alumina membranes (AAM) were successfully fabricated by electrodeposition. X-ray diffraction (XRD) pattern indicates that the crystallites of FePt Fe3Pt nanowires embedded in AAM are face centered cubic structure. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) reveal that the diameter and the length of nanowires are about 60 nm and 1 μm, respectively. The magnetic hysteresis loop demonstrates that the arrays of FePt Fe3Pt nanowires system exhibit uniaxial magnetic anisotropy with the easy magnetization direction along the nanowire axes owing to the large shape anisotropy.

Simplified fabrication and electrical analysis of crystalline silver nanowire

Silver nanowires have been fabricated using electrochemical deposition within the confined nanochannels of anodic alumina membrane on aluminum substrate. The characterization of structure, morphology, and composition indicates that the silver nanowires are uniform with about 50 nm diameter corresponding to the pore diameter of the anodic alumina membrane and almost single crystal with preferred growth along the [111] direction. Electrical measurements at room temperature showed that these silver nanowires were high conductive with a conductivity of approximately 0.13×105 S/cm. Also, individual silver nanowires were investigated by measuring current as a function of bias voltage until the point of failure. This study will be very useful for the development of future nanoelectronic devices and circuits that employ Ag nanowires.

Study of a Single InSb Nanowire Fabricated via DC Electrodeposition in Porous Templates

InSb nanowire arrays have been fabricated by direct current electrodeposition inside the nanochannels of anodic alumina membranes without subsequent annealing. After Au contacts were patterned to the nanowires using electron beam lithography, photoresponse studies were conducted. Absorbance peaks were also recorded from free suspending nanowires. A significant response was observed when the wires were exposed to visible light and infrared absorption peaks were observed during absorption experiment. Comparisons were also made between single and multiple nanowires' responses. The nanowires also conduct almost no current in the dark, but when hit with light, they conduct 10,000 times more current. This photoconducting property could lead to a variety of tiny optoelectronic devices potentially useful in future generations of nanoelectronics and chemical sensors.

Electrochemical Growth of InSb Nanowires and Report of a Single Nanowire Field Effect Transistor

InSb nanowires with high crystalline properties are synthesized with a diameter of 200 nm via direct current electrodeposition method inside the nanochannels of anodic alumina membranes. For the first time, the characteristics of field effect transistors based on InSb nanowires synthesized via electrochemistry is presented. A single InSb nanowire is used as a channel with gold source and drain contacts. A P ++ silicon substrate is used as the back-gate contact. Both nanowire synthesis and device fabrication are performed at room temperature and nanowire hole mobility is measured to be 57 cm 2 V -1 S -1 suggesting high structural quality of the as-grown InSb nanowires.

Templated Fabrication of InSb Nanowires for Nanoelectronics

Among various ways to produce nanowires, anodic alumina membrane‐ (AAM‐) based synthesis has constantly received much attention, because AAM has a uniform and parallel porous nanostructure which makes it an ideal template material for fabricating highly ordered nanostructures. In this paper, we report fabrication of InSb nanowire arrays with diameter of 200 nm and 30 nm by direct current electrodeposition inside the nanochannels of anodic alumina membranes without subsequent annealing. The nanowires have four major growth directions, (220) being the most dominant with structure defects such as twins. The transmission electron microscopy (TEM) and scanning electron microscopy (SEM) results demonstrate that these InSb nanowires are uniform with diameters about 200 nm and 30 nm, corresponding to the pore diameter of the AAMs. The I‐V measurement of a single nanowire is also reported with encouraging preliminary results.

Electrochemical Fabrication of InSb Nanowires using Porous Alumina Membrane and their Characterization

ABSTRACTAmong various ways to produce nanowires; anodic alumina membrane (AAM) based synthesis has constantly received much attention because AAM possess a uniform and parallel porous structure which makes them an ideal template material for creating highly ordered nanostructures. In this paper we report fabrication of InSb nanowire arrays with diameter of 200 nm and 30 nm by direct current electrodeposition inside the nanochannels of anodic alumina membranes without subsequent annealing. The nanowires have four major growth direction, [220] being the most dominant with structure defects such as twins. The transmission electron microscopy (TEM) and scanning electron microscopy (SEM) results demonstrate that these InSb nanowires are uniform with diameters about 200 nm and 30 nm, corresponding to the pore diameter of the AAMs. The nanowires also conduct almost no current in the dark, but when hit with light, they conduct 10,000 times more current. This photoconduction property could lead to a variety of tiny optoelectronic devices potentially useful in future generations of nanoelectronics and chemical sensors. The light-induced conductivity increase and the temperature dependent behavior of the nanowires are also reported.

Template synthesis of LaMnO 3+ δ ordered nanowire arrays by converse diffusion or convection

A method, whereby metal ions and precipitation reagents were transported in the nanochannels of anodic alumina membrane (AAM) templates by converse diffusion or convection and reacted in situ to form into one-dimensional nanostructure of the precursor, was developed. A high-aspect ratio nanowire array of the LaMnO 3+ δ was prepared by this method. Electron microscope images showed that the LaMnO 3+ δ nanowire array was abundant, uniformly distributed and well-ordered in large area. The individual nanowires are about 60 nm in diameter and their length corresponds to the thickness of the applied AAM template. The analysis of X-ray diffractions demonstrated that the LaMnO 3+ δ nanowires are pseudocubic with typical perovskite lattice parameter.

Fabrication of Highly Ordered InSb Nanowire Arrays by Electrodeposition in Porous Anodic Alumina Membranes

Highly ordered near-stoichiometrical polycrystalline InSb nanowire arrays have been fabricated by direct current (dc) electrodeposition inside the nanochannels of anodic alumina membranes (AAMs) and subsequent annealing. X-ray diffraction patterns and X-ray energy dispersion analysis reveal the change of crystal structure and the ratio of indium to antimony due to the deposition potential. The results show that cubic-phase InSb nanowire arrays can be achieved by using certain deposition potential and subsequent annealing. Transmission electron microscopy and scanning electron microscopy results demonstrate that these InSb nanowires are uniform with diameters about , corresponding to the pore diameter of the AAMs. Raman spectrum further demonstrates the InSb nanowire with high crystal quality.

Fabrication of ordered InN nanowire arrays and their photoluminescence properties

Semiconductor InN nanowire arrays were uniformly assembled into the hexagonally ordered nanochannels of anodic alumina membranes (AAM) through the direct reaction of indium and ammonia. The morphology and microstructures of sample were characterized by X-ray diffraction, scan electron microscopy, and transmission electron microscopy. A broad blue–green photoluminescence (PL) band in the wavelength range of 300–650 nm was observed from the InN nanowires assembly system (InN/AAM). A blue shift of the bandgap emission compared with that of bulk InN might be ascribed to the quantum confinement effect size and the interaction between the ordered InN nanowires and AAM.

Single Crystal Ni5Zn21 Nanowire Arrays Fabricated by Electrodeposition in Anodic Alumina Membranes

Abstract Large-area, high-filling rate, uniform, and single-crystal Ni5Zn21 nanowire arrays have successfully been synthesized by dc electrodeposition into the nanochannels of anodic alumina membranes (AAM).

Electrochemical synthesis of ordered alumina nanowire arrays

Ordered Al2O3 nanowire arrays embedded in the nanochannels of anodic alumina membranes (AAMs) were synthesized by electrodepostion at room temperature. Our synthetic route yielded large quantities of Al2O3 nanowires of uniform size and shape that are ~40 µm long with diameters of 70 nm. The Al2O3 nanowire structures were characterized by scanning and transmission electron microscopies, high-resolution transmission electron microscopy, energy dispersive spectroscopy and X-ray photoelectron spectroscopy.

Fabrication and optical properties of large-scale uniform zinc oxide nanowire arrays by one-step electrochemical deposition technique

Semiconductor ZnO nanowire arrays were fabricated by one-step electrochemical deposition technique based on ordered nanoporous alumina membrane. Their microstructures were characterized by transmission electron microscopy, Raman spectrum, and scanning electron microscopy. The results indicate that the ZnO nanowire array is uniformly assembled into the nanochannels of anodic alumina membranes (AAM). It is found that photoluminescence spectrum of the ZnO/AAM assembly system depends on the excitation wavelength in the visible region, which is attributed to different types of oxygen vacancies in the ZnO nanowires.

Morphology and Raman scattering spectrum of GaN nanowires embedded in nanochannels of template

The hexagonal wurtzite GaN nanowires embedded in the nanochannels of anodic alumina membrane were achieved by the direct reaction of Ga vapour with a constant flowing ammonia atmosphere. X-ray diffraction (XRD), scanning electron microscopy and transmission electron microscopy were used to measure the size and structures of the samples. The Raman scattering spectrum of ordered GaN nanowires was studied. The Raman spectrum of the GaN nanowire arrays is consistent with the hexagonal wurtzite structure GaN, in agreement with XRD observation. The E2(high), E1(TO), and A1(TO) phonon frequencies at 563, 553, and 529 cm-1 show the low-energy shifts, respectively. The shifts and band broadening of the Raman modes result from the nanosize effect.

Effect of colloid characteristics on the fabrication of ZnO nanowire arrays by electrophoretic deposition

In this study ZnO colloidal suspensions with varied characteristics were synthesized by varying the amount of added sodium hydroxide. The template-mediated preparation for nanosized ZnO arrays was conducted by electrophoretic deposition in the nanochannels of anodic alumina membranes. The effect of colloid characteristics on the deposition of ZnO nanowire arrays was investigated, and the related deposition mechanisms, morphologies and optical properties of the deposits were discussed. The deposited ZnO nanoarrays were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and photoluminescence (PL) studies. It was found that both the morphology and the deposition rate of ZnO nanowire arrays were influenced by the pH of the suspension and the applied voltage. The particle surface charge and size changed with the pH of the suspension, which in turn affected the deposition characteristics. The deposition rate of nanowire arrays was high at the initial stage and then approached a saturation value. The deposition rate also increased with increasing zeta potential of the particles and the applied voltage for EPD of ZnO nanowires. The photoluminescence properties of ZnO arrays were largely determined by particle size and surface properties of the nanoparticles comprising the nanowire arrays.

Structure and magnetic property of Ni-Cu alloy nanowires electrodeposited into the pores of anodic alumina membranes

Ordered Ni-Cu alloy nanowire arrays embedded in the hexagonally ordered nanochannels of anodic alumina membranes (AAMs) were fabricated by electrodeposition. The x-ray diffraction, x-ray energy dispersion spectrum, scanning and transmission electron microscopy were utilized to characterize the Ni-Cu alloy nanowire arrays. The results reveal that single crystalline Ni-Cu alloy nanowires are single crystal and that the atomic composition of Ni and Cu is very close to a 1 : 1 stoichiometry. Magnetic hysteresis loop shows that the Ni-Cu alloy nanowire arrays embedded in AAMs have perpendicular magnetic anisotropy, indicating their potential applications in perpendicular magnetic recording.

Fabrication and magnetic properties of highly ordered Co 16 Ag 84 alloy nanowire array

Highly ordered Co-Ag alloy nanowire arrays embedded in the nanochannels of anodic alumina membranes (AAMs) were successfully fabricated using electrodeposition. Scanning electron microscopy and transmission electron microscopy observations revealed that the ordered Co-Ag alloy nanowires were uniformly assembled into the hexagonally ordered nanochannels of the AAMs. Magnetic measurements showed that the perpendicular coercivity (Hc⊥) of the ordered nanowire arrays increased dramatically as the annealing temperature (Ta) rose from 300 °C, reached its maximum (183 Oe) at 400 °C and then decreased sharply as Ta further increased beyond 400 °C. However, there was little change in the parallel coercivity (Hc∥) of the nanowire arrays during the annealing process. The mechanism of this phenomenon was attributed to the special structure of the AAMs and nanowires.

Fabrication and Structural Characterization of Large-Scale Uniform SnO2 Nanowire Array Embedded in Anodic Alumina Membrane

Semiconductor SnO2 nanowire arrays were fabricated by electrochemical deposition and thermal oxidizing methods based on highly ordered nanoporous alumina membrane. Their microstructures were characterized by X-ray diffraction, transmission electron microscopy, Raman spectrum, and scanning electron microscopy. The results indicate that the SnO2 nanowire array with cassiterite polycrystalline structure is uniformly assembled into the hexagonally ordered nanochannels of anodic alumina membranes. There are three phases (Sn, SnO, and SnO2) coexisting when the as-deposited assembly system is annealed at 823 K. However, only the SnO2 cassiterite phase is detected when the assembly system is annealed at 923 K.

Micro-Raman investigation of GaN nanowires prepared by direct reaction Ga with NH 3

Ordered crystalline GaN nanowires embedded in the nanochannels of anodic alumina membrane (AAM) were achieved by direct reaction Ga with NH 3. The impact of reaction temperatures on Raman spectroscopic properties of GaN nanowires is investigated. X-ray diffraction and transmission electron microscopy (TEM) observations demonstrate that the crystalline GaN nanowires have hexagonal wurtzite structure. The hexagonal wurtzite structure GaN nanowires prepared at 960 °C are about 40 nm in diameter and up to several hundreds of micrometers in length.