Thin layers of indium tin oxide are widely used as transparent coatings and electrodes in solar energy cells, flat-panel displays, antireflection coatings, radiation protection and lithium-ion battery materials, because they have the characteristics of low resistivity, strong absorption at ultraviolet wavelengths, high transmission in the visible, high reflectivity in the far-infrared and strong attenuation in the microwave region. However, there is often a trade-off between electrical conductivity and transparency at visible wavelengths for indium tin oxide and other transparent conducting oxides. Here, we report the growth of layers of indium tin oxide nanowires that show optimum electronic and photonic properties and demonstrate their use as fully transparent top contacts in the visible to near-infrared region for light-emitting devices

We report the observation of urchin-like nanostructures consisting of high-density spherical nanotube radial arrays of vanadium oxide nanocomposite, successfully synthesized by a simple chemical route using an ethanolic solution of vanadium tri-isopropoxide and alkyl amine hexadecylamine for 7 days at 180 o C. The results show that the growth process of the NanoUrchin occurs in stages, starting with a radial self-organized arrangement of lamina followed by the rolling of the lamina into nanotubes. The longest nanotubes are measured to be several micrometers in length with diameters of 120 nm and hollow centers typically measured to be 75 nm. The NanoUrchin have an estimated density of nanotubes of 40 sr -1 . The tube walls comprise layers of vanadium oxide with the organic surfactant intercalated between atomic layers. The interlayer distance is measured to be 2.9 ± 0.1 nm and electron diffraction identified the vanadate phase in the VO x nanocomposite as orthorhombic V 2 O 5 . These nanostructures may be used as three-dimensional composite materials and as supports for other materials.4

The anodic behavior of highly doped ͑Ͼ10 18 cm −3 ͒ n-InP in aqueous KOH was investigated. Electrodes anodized in the absence of light in 2-5 mol dm −3 KOH at a constant potential of 0.5-0.75 V ͑SCE͒, or subjected to linear potential sweeps to potentials in this range, were shown to exhibit the formation of a nanoporous subsurface region. Both linear sweep voltammograms and current-time curves at constant potential showed a characteristic anodic peak, corresponding to formation of the nanoporous region. No porous region was formed during anodization in 1 mol dm −3 KOH. The nanoporous region was examined using transmission electron microscopy and found to have a thickness of some 1-3 m depending on the anodization conditions and to be located beneath a thin ͑typically ϳ40 nm͒, dense, near-surface layer. The pores varied in width from 25 to 75 nm and both the pore width and porous region thickness were found to decrease with increasing KOH concentration. The porosity was approximately 35%. The porous layer structure is shown to form by the localized penetration of surface pits into the InP, and the dense, near-surface layer is consistent with the effect of electron depletion at the surface of the semiconductor.

The early stages of nanoporous layer formation, under anodic conditions in the absence of light, were investigated for n-type InP with a carrier concentration of ϳ3 ϫ 10 18 cm −3 in 5 mol dm −3 KOH and a mechanism for the process is proposed. At potentials less than ϳ0.35 V, spectroscopic ellipsometry and transmission electron microscopy ͑TEM͒ showed a thin oxide film on the surface. Atomic force microscopy ͑AFM͒ of electrode surfaces showed no pitting below ϳ0.35 V but clearly showed etch pit formation in the range 0.4-0.53 V. The density of surface pits increased with time in both linear potential sweep and constant potential reaching a constant value at a time corresponding approximately to the current peak in linear sweep voltammograms and current-time curves at constant potential. TEM clearly showed individual nanoporous domains separated from the surface by a dense ϳ40 nm InP layer. It is concluded that each domain develops as a result of directionally preferential pore propagation from an individual surface pit which forms a channel through this near-surface layer. As they grow larger, domains meet, and the merging of multiple domains eventually leads to a continuous nanoporous sub-surface region.

Brammertz, G.; Heyns, M.; Newcomb, Simon B.; Afanas'ev, V. V.;Hurley, Paul K.

Access to the full text of the published version may require a subscription. The relationship between the nanoscale structure of vanadium pentoxide nanotubes and their ability to accommodate Li + during intercalation/deintercalation is explored. The nanotubes are synthesized using two different precursors through a surfactant-assisted templating method, resulting in standalone VO x (vanadium oxide) nanotubes and also nanourchin. Under highly reducing conditions, where the interlaminar uptake of primary alkylamines is maximized, standalone nanotubes exhibit near-perfect scrolled layers and longrange structural order even at the molecular level. Under less reducing conditions, the degree of amine uptake is reduced due to a lower density of V 4+ sites and less V 2 O 5 is functionalized with adsorbed alkylammonium cations. This is typical of the nano-urchin structure. Highresolution TEM studies revealed the unique observation of nanometer-scale nanocrystals of pristine unreacted V 2 O 5 throughout the length of the nanotubes in the nano-urchin. RightsElectrochemical intercalation studies revealed that the very well ordered xerogel-based nanotubes exhibit similar specific capacities (235 mAh g -1 ) to Na + -exchange nanorolls of VO x (200 mAh g -1 ). By comparison, the theoretical maximum value is reported to be 240 mAh g -1 .The VOTPP-based nanotubes of the nano-urchin 3-D assemblies, however, exhibit useful Submitted to 3 charge capacities exceeding 437 mAh g -1 , which is a considerable advance for VO x based nanomaterials and one of the highest known capacities for Li + intercalated laminar vanadates.

In this work, we present the results of an investigation into the effectiveness of varying ammonium sulphide (NH4)2S concentrations in the passivation of n-type and p-type In0.53Ga0.47As. Samples were degreased and immersed in aqueous (NH4)2S solutions of concentrations 22%, 10%, 5%, or 1% for 20 min at 295 K, immediately prior to atomic layer deposition of Al2O3. Multi-frequency capacitance-voltage (C-V) results on capacitor structures indicate that the lowest frequency dispersion over the bias range examined occurs for n-type and p-type devices treated with the 10%(NH4)2S solution. The deleterious effect on device behavior of increased ambient exposure time after removal from 10%(NH4)2S solution is also presented. Estimations of the interface state defect density (Dit) for the optimum 10%(NH4)2S passivated In0.53Ga0.47As devices extracted using an approximation to the conductance method, and also extracted using the temperature-modified high-low frequency C-V method, indicate that the same defect is present over n-type and p-type devices having an integrated Dit of ∼2.5×1012 cm−2 (±1×1012 cm−2) with the peak density positioned in the middle of the In0.53Ga0.47As band gap at approximately 0.37 eV (±0.03 eV) from the valence band edge. Both methods used for extracting Dit show very good agreement, providing evidence to support that the conductance method can be applied to devices incorporating high-k oxides on In0.53Ga0.47As.

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