Ni Nanodots Research Articles

Self-assembly of faceted Ni nanodots on Si(111)

We report the formation of Ni nanodots on Si(111). Island density is varied by annealing temperature and time and is studied using atomic force microscopy (AFM) and magnetic force microscopy. Activation energies of 0.09±0.02 and 0.31±0.05eV are observed for the formation of these islands. These are associated with Ni surface self-diffusion across the (111) and (110) Ni facets, respectively. For brief 500°C anneals, regular nanodots are observed with self-limiting sizes of height ∼16nm and area 180nm×260nm, while density exhibits a power-law time dependence with exponent 1.13±0.12. AFM analysis reveals a “truncated hut” shape consistent with (110) top and (111) sidewall surfaces.

Controlled growth of GaN nanowires by pulsed metalorganic chemical vapor deposition

Controlled and reproducible growth of GaN nanowires is demonstrated by pulsed low-pressure metalorganic chemical vapor deposition. Using self-assembled Ni nanodots as nucleation sites on (0001) sapphire substrates we obtain nanowires of wurtzite-phase GaN with hexagonal cross sections, diameters of about 100nm, and well-controlled length. The nanowires are highly oriented and perpendicular to the growth surface. The wires have excellent structural and optical properties, as determined by x-ray diffraction, cathodoluminescence, and Raman scattering. The x-ray measurements show that the nanowires are under a complex strain state consistent with a superposition of hydrostatic and biaxial components.

Fabrication of Nanodot Arrays on Si by Pulsed Laser Deposition Using Anodic Aluminum Oxide Nanopore Membrane as Mask

We demonstrate the fabrication of metal and semiconductor nanodot arrays on Si by pulsed laser deposition using an anodic alumina membrane as a mask. A Hexagonal-close-packed nanopore membrane mask was fabricated by the anodic oxidation of aluminum sheet. Pulsed laser deposition of Ag, Ni, ZnO, and Er-doped Si (Si:Er) nanodots was performed on a Si substrate to which an alumina membrane mask adheres by van der Waals interaction. Highly ordered arrays of Ag, Ni, ZnO, and Si:Er nanodots with average diameters ranging from 55 to 86 nm and a periodicity of ∼100 nm were obtained. Also, the time-resolved images of laser-produced plasma plumes were analyzed to examine the dynamical properties of the ejected materials.

Preparation of Ni Nanodot and Nanowire Arrays Using Porous Alumina on Silicon as a Template Without a Conductive Interlayer

Recently, many nanostructures have been prepared successfully through electrodeposition of materials into anodic porous alumina coated with a conductive layer on the bottom. Here, the fabrication of Ni nanostructures using anodic porous alumina on Si as a template without a conductive interlayer is investigated. Morphologies of Ni nanostructures were dominated by the applied voltages and an excellent replication capability for this method was revealed. The novel electrodeposition behavior in this study is quite different from the "bottom-up" electrodeposition in conventional template-mediated growth of materials. © 2004 The Electrochemical Society. All rights reserved.

Scanning thermal microwave resonance microscopy of Ni nanodots

Ni nanodots of random shape were deposited electrolytically on a mica substrate covered by Au with [111] texture. The dots had a maximum size of 260 nm in height and 150 nm in diameter. These dots were investigated by conventional and locally resolved ferromagnetic resonance (FMR). We present for the first time FMR spectra taken from a single nanodot by detection of the thermoelastic response of the microwave absorption in the dot by a scanning tunneling microscope (STM). The single Ni dots show sharp separate resonance lines, governed by the influence of shape anisotropy. We could prove that the expansion of the sample detected by the z-piezo voltage of the STM signal in the FMR line is due to the thermoelastic effect caused by heating through the absorbed microwave power.

Tunable magnetic properties of metal ceramic composite thin films

We have developed a novel thin film processing method based upon pulsed laser deposition to process nanocrystalline magnetic materials with accurate size and interface control. Using this method, single domain nanocrystalline Fe and Ni particles in 5–10 nm size range embedded in amorphous as well as crystalline alumina have been produced. Magnetization measurements of these layered thin films as function of field and temperature were carried out using a superconducting quantum interference device magnetometer. The size of Fe and Ni nanodots measured using transmission electron microscopy and calculated using magnetic data are in excellent agreement with each other.

Tunable Magnetic Properties in Metal Ceramic Composite Thin Films

ABSTRACTWe have developed a novel thin film processing method based upon pulsed laser deposition to process nanocrystalline magnetic materials with accurate size and interface control. Using this method, single domain nanocrystalline Fe and Ni particles in 5-10 nm size range embedded in amorphous as well as crystalline alumina have been produced. Magnetization measurements of these layered thin films as function of field and temperature were carried out using a superconducting quantum interference device magnetometer. Hysteresis below blocking temperature have been found to be consistent with the Stoner-Wohlfarth type behavior. The size of Fe and Ni nanodots measured using transmission electron microscopy and calculated using magnetic data are in excellent agreement with each other.