We report here an electrodeposition route for the preparation of oriented and well-defined ZnO nanostructures by kinetically controlling growth rates various facets deposit appropriate capping agents. demonstrated that adsorption Cl(-) takes places preferentially onto (0001) planes to hinder crystal along c-axis, results in formation platelet-like crystals. It is also shown morphology evolved from hexagonal tapers rods rhombohedral changing compositions Furthermore, strong UV emissions at...

A multi-mode network typically consists of multiple heterogeneous social actors among which various types interactions could occur. Identifying communities in a can help understand the structural properties network, address data shortage and unbalanced problems, assist tasks like targeted marketing finding influential within or between groups. In general, membership groups often evolve gradually. dynamic both actor evolve, poses challenging problem identifying community evolution. this work,...

We report on an AlN/AlGaN superlattice approach to grow high-Al-content thick n+-AlGaN layers over c-plane sapphire substrates. Insertion of a set superlattices is shown significantly reduce the biaxial tensile strain, thereby resulting in 3-μm-thick, crack-free Al0.2Ga0.8N layers. These high-quality, low-sheet-resistive are key importance avoid current crowding quaternary AlInGaN multiple-quantum-well deep-ultraviolet light-emitting diodes

This paper examines the concept of strain balance in alternate tensile and compressively strained layers using classical elasticity theory clarifies a number issues associated with definition misfit. The strain-balance criteria are derived from zero average in-plane stress condition compared against two commonly used thickness weighted models, based on lattice parameter respectively. zero-stress fully accounts for differences elastic properties layers, establishes true strain-balanced...

We report on an approach of using AlN/AlGaN superlattices (SLs) for threading-dislocation-density reduction to grow high quality thick AlGaN sapphire. Using x-ray diffraction (XRD) measurements and etch pits counting by atomic force microscopy, we show that the insertion SLs suppresses material mosaicity decreases threading dislocation density two orders magnitude, then eliminates cracking. Dislocation densities deduced from XRD results those chemical etching are in a good agreement.

We report the demonstration of a ZnO nanowire ultraviolet photodetector with top transparent electrode made few-layered graphene sheet. The nanowires have been synthesized using low-cost electrodeposition method. detector is shown to be visible-blind and present responsivity larger than 104 A/W in near range thanks high photoconductive gain nanowires. device exhibits peak at 370 nm wavelength shows sub bandgap response down 415 explained by an Urbach tail characteristic energy 83 meV....

We report on AlGaN multiple-quantum-well (MQW)-based deep ultraviolet light-emitting diodes over sapphire with peak emission at 278 nm. A new buffer layer growth process was used to reduce the number of defects and hence nonradiative recombination. The improved material quality carrier confinement resulted in pulsed powers as high 3 mW nm a significantly reduced deep-level-assisted long-wavelength emission.

a-plane GaN templates and coalesced epitaxial lateral overgrown (ELOG) films on r-plane sapphire substrates were investigated by x-ray diffraction (XRD). The found to have [0001]-oriented stripe-features, which is related anisotropic mosaicity. For the mosaic blocks, mosaicity reached largest smallest values along [11̄00] [0001] directions. ELOG procedure with SiO2 mask stripes perpendicular direction limits preferable growth this direction, thereby enhances growth. This leads large-area,...

Rote Emission mit λem=614 nm zeigt der Europium(III)-Komplex [Eu(tta)3dpbt] (1), wenn er durch Zweiphotonenanregung sensibilisiert wird. Der große Zweiphotonenabsorptionsquerschnitt und die hohe Lumineszenzeffizienz führen zu einem wirksamen Anregungsprozess.

In this letter, we report the pulsed atomic-layer epitaxy of ultrahigh-quality AlN epilayers and AlN/Al0.85Ga0.15N multiple quantum wells (MQWs) on basal plane sapphire substrates. Symmetric asymmetric x-ray diffraction (XRD) measurements room-temperature (RT) photoluminescence (PL) were used to establish ultrahigh structural optical quality. Strong band-edge RT PL at 208 228 nm was obtained from MQWs. These data clearly their suitability for sub-250-nm deep UV emitters.

We report self-induced growth of vertically aligned (i.e. along the [111] direction), free-standing InAs nanowires on Si(111) substrates by solid-source molecular beam epitaxy. Implementation an ultrathin amorphous SiO(x) mask facilitated epitaxial nanowire growth, as confirmed high-resolution x-ray diffraction 2theta-omega scans and transmission electron microscopy. Depending temperature (in range 400-520 degrees C) substantial size variation both length diameter was found under...

A topic taxonomy is an effective representation that describes salient features of virtual groups or online communities. consists nodes. Each internal node defined by its vertical path (i.e., ancestor and child nodes) horizonal list attributes (or terms). In a text-dominant environment, can be used to flexibly describe group's interests with varying granularity. However, the stagnant nature may fail timely capture dynamic change interest. This article addresses problem how adapt accumulated...

The extraction and separation of rare earths (REs) from nitrate medium or chloride using bifunctional ionic liquid extractants (Bif-ILEs) [trialkylmethylammonium][di(2-ethylhexyl)orthophosphinate] ([A336][P507]) [trialkylmethylammonium][di-2-ethylhexylphosphate] ([A336][P204]) in n-heptane were investigated this report. factor (β) values indicated that [A336][P507] [A336][P204] could be suitable for the heavy REs(III) light medium. Especially, medium, β as extractant Tm/Er (3.36), Yb/Tm...

Abstract Aims To examine incidence density rate and correlates of incident diabetes mellitus in a cohort HIV ‐infected individuals compared with matched non‐ persons. Methods Data were obtained from the South Carolina Medicaid system enhanced / AIDS Reporting System surveillance database for persons ≥ 18 years age who had been attended to during period 1994 2011. Time‐dependent proportional hazards analysis marginal structural models used analyse data. Results A total 13 632 (6816, 1:1...

We present a detailed high-pump-current study of self-heating effects in ultraviolet light-emitting diodes (LEDs) grown on sapphire. For deep LEDs sapphire, our results establish to be primary cause premature power saturation under dc pumping. Even the flip-chip packaged devices undergo steady-state temperature rise about 70 °C at pump current only 50 mA (at 8 V) resulting significant decrease LED output. Temperature values estimated from peak emission wavelength shifts and micro-Raman...

Novel, current collapse free, double heterostructure AlGaN/InGaN/GaN field effect transistors (DHFETs) are fabricated on the insulating SiC substrates. The simulations show that a combined of bandgap offsets and polarization charges provides an excellent 2D carrier confinement. These devices demonstrate output RF powers as high 4.3 W/mm in CW mode 6.3 pulsed mode, with gain compression low 4 dB.

We report on 269 nm emission deep ultraviolet light-emitting diodes (LEDs) over sapphire. The material quality, device design, and contact processing sequence yielded devices with external quantum efficiencies as high 0.4% for a pumped pulse current of 200 mA 0.32% dc pump 10 mA. For module two LEDs connected in series, record continuous-wave power 0.85 mW (at 40 mA) wall plug efficiency 0.16% dc) were measured.

The characteristics of a novel nitride based field-effect transistor combining SiO/sub 2/ gate isolation and an AlGaN/InGaN/GaN double heterostructure design (MOSDHFET) are reported. with InGaN channel layer significantly improves confinement the two-dimensional (2-D) electron gas compensates strain modulation in AlGaN barrier resulting from voltage modulations. These decrease total trapped charge hence current collapse. combination improved carrier confinement/strain management results...

Optimization of the migration-enhanced metalorganic chemical vapor deposition and further optimization contact active layer design for 280nm light-emitting diodes resulted in large improvement cw pulsed output power a superior spectrum purity. The ratio main peak to background luminescence determined by detection system is higher than 2000:1 at 20mA dc. on-wafer was measured be 255μW popped up exceeding 1mW packaged device under 25mA dc 9mW pulse 200mA. maximum wall-plug-efficiency 0.67% obtained

Temperature-dependent photoluminescence (PL) measurements were performed for A-plane and C-plane bulk AlN single crystals epitaxial layers on sapphire. A strong near-band-edge (NBE) emission deep-level luminescence observed. At low excitations, the spectra are dominated by free bound excitonic transitions their LO-phonon replicas. high broadening redshift of NBE band is attributed to dense electron–hole plasma formation. The PL differences epilayers explained expansion peculiarities.

We report on the development of AlGaN based deep ultraviolet (DUV) light-emitting diodes (LEDs) grown by migration-enhanced metalorganic chemical vapor deposition (MEMOCVD). Improved quality has allowed us to achieve milliwatt-power at wavelengths ranging from 365 265 nm. For 295 and 280 nm LEDs, record CW powers with wall-plug-efficiency approaching 1.0% were realized. The power reached 1.2 1.0 mW 20 mA for respectively. A multiple-chip package (UV lamp) emitted 11 wavelength Under pulse...