Site controlled red-yellow-green light emitting InGaN quantum discs on nano-tipped GaN rods

We report a method of growing site controlled InGaN multiple quantum discs (QDs) at uniform wafer scale on coalescence free ultra-high density (>80%) nanorod templates by metal organic chemical vapour deposition (MOCVD). The dislocation and coalescence free nature of the GaN space filling nanorod arrays eliminates the well-known emission problems seen in InGaN based visible light sources that these types of crystallographic defects cause. Correlative scanning transmission electron microscopy (STEM), energy-dispersive X-ray (EDX) mapping and cathodoluminescence (CL) hyperspectral imaging illustrates the controlled site selection of the red, yellow and green (RYG) emission at these nano tips. This article reveals that the nanorod tips' broad emission in the RYG visible range is in fact achieved by manipulating the InGaN QD's confinement dimensions, rather than significantly increasing the In%. This article details the easily controlled method of manipulating the QDs dimensions producing high crystal quality InGaN without complicated growth conditions needed for strain relaxation and alloy compositional changes seen for bulk planar GaN templates.

Supercapattery based on binder-free Co3 (PO4)2·8H2O multilayer nano/microflakes on nickel foam

A binder-free cobalt phosphate hydrate (Co3(PO4)2·8H2O) multilayer nano/microflake structure is synthesized on nickel foam (NF) via a facile hydrothermal process. Four different concentrations (2.5, 5, 10, and 20 mM) of Co2+ and PO4–3 were used to obtain different mass loading of cobalt phosphate on the nickel foam. The Co3(PO4)2·8H2O modified NF electrode (2.5 mM) shows a maximum specific capacity of 868.3 C g–1 (capacitance of 1578.7 F g–1) at a current density of 5 mA cm–2 and remains as high as 566.3 C g–1 (1029.5 F g–1) at 50 mA cm–2 in 1 M NaOH. A supercapattery assembled using Co3(PO4)2·8H2O/NF as the positive electrode and activated carbon/NF as the negative electrode delivers a gravimetric capacitance of 111.2 F g–1 (volumetric capacitance of 4.44 F cm–3). Furthermore, the device offers a high specific energy of 29.29 Wh kg–1 (energy density of 1.17 mWh cm–3) and a specific power of 4687 W kg–1 (power density of 187.5 mW cm–3).

Comparative structural-vibrational study of nano-urchin and nanorods of vanadium oxide

We present a comparative structural–vibrational study of nanostructured systems of V2O5: nano-urchin (VONURs) which are spherical structures composed of a radially oriented array of VOx nanotubes (VOx-NTs) with a volumetric density of ∼40 sr–1, and vanadium oxide nanorods (VOx-NRDs) with an average length of ∼100 nm. The Raman scattering spectrum of the nano-urchin exhibits a band at 1014 cm–1 related to the distorted gamma conformation of the vanadium pentoxide (γ-V5+). The infrared vibrational spectra of the nanorods sample also exhibit a distorted laminar V2O5 structure with evidence observed for quadravalent V4+ species at 921 cm–1.

Electrochemical formation of ordered pore arrays in InP in KCl

Pores are formed electrochemically in n-InP in KCl electrolytes with concentrations of 2 mol dm-3 or greater. The pore morphology is similar to what is seen in other halide-based electrolytes. At low potentials, crystallographically oriented (CO) pores are formed. At higher potentials, current-line oriented (CLO) pores are formed. Crystallographically oriented pore walls are observed for both pore morphologies. When formed at a constant current, potential oscillations are observed which have been correlated to oscillations in the pore width. The CLO pore wall smoothness and overall uniformity increase as KCl concentration is increased. The porous structures formed in KCl compare favourably with those formed in the more acidic or alkaline electrolytes that are typically used to form these structures.

Resist-substrate interface tailoring for generating high density arrays of Ge and Bi2Se3 nanowires by electron beam lithography

The authors report a chemical process to remove the native oxide on Ge and Bi2Se3 crystals, thus facilitating high-resolution electron beam lithography (EBL) on their surfaces using a hydrogen silsesquioxane (HSQ) resist. HSQ offers the highest resolution of all the commercially available EBL resists. However, aqueous HSQ developers such as NaOH and tetramethylammonium hydroxide have thus far prevented the fabrication of high-resolution structures via the direct application of HSQ to Ge and Bi2Se3, due to the solubility of components of their respective native oxides in these strong aqueous bases. Here we provide a route to the generation of ordered, high-resolution, high-density Ge and Bi2Se3 nanostructures with potential applications in microelectronics, thermoelectric, and photonics devices.                         

Ordered magnetic dipoles: controlling anisotropy in nanomodulated continuous ferromagnetic films

In this paper, the research focus is how to entangle magnetic dipoles to control/engineer magnetic properties of different devices at a submicron/nano scale. Here, we report the generation of synthetic arrays of tunable magnetic dipoles in a nanomodulated continuous ferromagnetic film. In-plane magnetic field rotations in modulated Ni 45Fe 55 revealed various rotational symmetries of magnetic anisotropy due to dipolar interaction with a crossover from lower to higher fold as a function of modulation geometry. Additionally, the effect of aspect ratio on symmetry shows a novel phase shift of anisotropy, which could be critical to manipulate the overall magnetic properties of the patterned film. The tendency to form vortex is in fact found to be very small, which highlights that the strong coupling between metastable dipoles is more favorable than vortex formation to minimize energy in this nanomodulated structure. This has further been corroborated by the observation of step hysteresis, magnetic force microscopy images of tunable magnetic dipoles, and quantitative micromagnetic simulations. An analytical expression has been derived to estimate the overall anisotropy accurately for nanomodulated film having low magnetocrystaline anisotropy. Derived mathematical expressions based on magnetic dipolar interaction are found to be in good agreement with our results.