Giant inverse Faraday effect in a plasmonic crystal ring

Circularly polarized electromagnetic wave impinging on a conducting ring with a two-dimensional electron channel generates a circulating DC plasmonic current resulting in an inverse Faraday effect in nanorings. We show that a large ring with periodically modulated width on a nanoscale, smaller or comparable with the plasmonic mean free path, supports plasmon energy bands. When circularly polarized radiation impinges on such a plasmonic ring, it produces resonant DC plasmonic current on a macro scale resulting in a giant inverse Faraday effect. The systems comprised of the concentric variable-width rings ("plasmonic disks") and stacked plasmonic disks ("plasmonic solenoids") amplify the generated constant magnetic field by orders of magnitude.

Red-blue-green solid state light sources using a narrow line-width green phosphor

We demonstrate that using a narrow line-width green phosphor with the peak wavelength closely aligned with the peak in the human eye sensitivity significantly improves the Luminous Efficacy of Radiation (LER) for Red-Green-Blue (RGB) emitters. Compared to the traditional RGB sources, the improvement in LER of 20 lm/W can be achieved. Combining the narrow band green phosphor with conventional wide band red and blue phosphors allows for trading off these improvements against the deviation from the Planckian locus for even higher LER. The light sources with the narrow line green phosphor are particularly promising for high energy efficiency and high intensity illumination, where somewhat compromises can be made in the color quality such as in automotive, outdoor spaces, industrial ware-houses, public places (train stations, airports) etc..

Nanometer size field effect transistors for terahertz detectors

Nanometer size field effect transistors can operate as efficient resonant or broadband terahertz detectors, mixers, phase shifters and frequency multipliers at frequencies far beyond their fundamental cut-off frequency. This work is an overview of some recent results concerning the application of nanometer scale field effect transistors for the detection of terahertz radiation.

Physics of Novel Amorphous Silicon High-Voltage Transistor

In this paper we describe the operation of a novel amorphous silicon high voltage transistor. Its attractive feature is that it can operate at source-drain voltages in excess of 400 volts but its characteristics are controlled by applying only a low bias (0-10 volts) to a gate electrode covering a small portion of the sourcedrain channel near to the source. The portion of the device over this gate electrode operates as a conventional amorphous silicon Field-Effect Transistor which injects electrons into the intrinsic amorphous silicon between this region and the drain electrode. We present experimental data showing the current-voltage characteristics of this new transistor as a function of geometry and demonstrate that the above model realistically describes its operation.

Density of Deep Bandgap States in Amorphous Silicon From the Temperature Dependence of Thin Film Transistor Current

We have measured the current-voltage characteristics of amorphous silicon thin film transistors (a-Si TFTs) over a wide range of temperatures (20 to 160°C) and determined the activation energy of the channel current as a function of gate bias with emphasis on the leakage current and subthreshold regimes. We propose a new method for estimating the density of localized states (DOS) from the dependence of the derivative of activation energy with respect to gate bias. This differential technique does not require knowledge of the flat-band voltage (VFB) and does not incorporate integration over gate bias. Using this Method, we have characterized the density of localized states with energies in the range 0.15–1.2 eV from the bottom of the conduction band and have found a wide peak in the DOS in the range of 0.8–0.95 eV below the conduction band. We have also observed that the DOS peak in the lower half of the bandgap increases in magnitude and shifts towards the conduction band as a result of thermal and bias stress. We also measured an overall increase in the DOS in the upper half of the energy gap and an additional peak, centered at 0.2 eV below the conduction band, which appear due to the applied stress. These results are in qualitative agreement with the defect pool Model [1,2].

Progress in the Preparation of Aluminum Nitride Substrates from Bulk Crystals

Large (11-mm diameter) single-crystal AlN boules have been prepared using sublimationrecondensation growth. X-ray topography shows that substrates prepared from those boules have a dislocation density of less than 500 cm-2, while the central region of these substrates was nearly dislocation-free. Rocking curves of less than 10 arcsecs have been obtained indicating the high quality of these crystals. The AlN substrates have been used to growth an AlGaN/AlN multiquantum well structure with excellent crystalline quality and with photoluminescence peaked at around 260nm. In addition, a UV LED with emission wavelength at 360nm has been fabricated. This is the first operating opto-electronic device demonstrated on an AlN substrate.

Electrical and noise characteristics of graphene field-effect transistors: ambient effects, noise sources and physical mechanisms

We fabricated a large number of single and bilayer graphene transistors and carried out a systematic experimental study of their low-frequency noise characteristics. Special attention was given to determining the dominant noise sources in these devices and the effect of aging on the current-voltage and noise characteristics. The analysis of the noise spectral density dependence on the area of graphene channel showed that the dominant contributions to the low-frequency electronic noise come from the graphene layer itself rather than from the contacts. Aging of graphene transistors due to exposure to ambient conditions for over a month resulted in substantially increased noise, attributed to the decreasing mobility of graphene and increasing contact resistance. The noise spectral density in both single and bilayer graphene transistors either increased with deviation from the charge neutrality point or depended weakly on the gate bias. This observation confirms that the low-frequency noise characteristics of graphene transistors are qualitatively different from those of conventional silicon metal-oxide-semiconductor field-effect transistors.

Systemic resistance to the antilipolytic effect of insulin in black and white women with visceral obesity

This study was designed to determine the role of visceral adipose tissue (VAT) accumulation in systemic fat metabolism and to compare this in black and white women who differ in their manifestations of upper body obesity. Systemic glycerol and free fatty acid (FFA) turnover rates (rates of appearance, Ra) were measured in the basal state and during a pancreatic euglycemic clamp in nondiabetic, premenopausal, obese black and white women with a wide range of VAT accumulation. The slopes of the regression equations predicting basal and insulin-suppressed RaGlycerol and RaFFA from VAT area, age, and fat mass or fat-free mass did not significantly differ between black and white women. VAT area was the best predictor of the %-suppressed RaGlycerol and RaFFA during the pancreatic clamp (partial r = 0.76, P < 0.0001 and partial r = 0.60, P < 0.05, respectively). Basal R(a)Glycerol, but not RaFFA, was lower in black than in white women (P < 0.05). During the clamp, black women showed greater insulin suppression of RaGlycerol than of RaFFA (P < 0.0001) and greater insulin suppression of RaGlycerol (P < 0. 05) but similar suppression of RaFFA compared with white women. These differences were independent of age, fat mass, or fat-free mass and were partly explained by a lower VAT in black women. Thus, in both races, VAT accumulation was associated with systemic resistance to the antilipolytic effect of insulin and, in obese black women, systemic lipolysis measured as glycerol turnover rate was more responsive to insulin suppression than were systemic FFA turnover rates.

Resting metabolic rate in obese, premenopausal black women

In the United States, obesity is more prevalent in black than in non-Hispanic white women. Because low resting metabolic rate (RMR) has been suggested as a risk factor for weight gain, we compared RMR in 22 black and 20 white obese [body mass index (BMI; in kg/m2) range: 28.9-48.6 and 26.9-44.1, respectively], weight-stable, premenopausal, nondiabetic women. RMR was measured on two or three different occasions within a 1-wk period. The black and white groups did not differ significantly in age, degree of fitness, BMI, fat mass, or fat-free mass (FFM). In each group, RMR was predicted independently by FFM but not by age, degree of fitness, body fat mass, or body fat distribution. The slopes of the equations predicting RMR from FFM in black and white groups were not significantly different. However, the black women had significantly lower RMRs than the white women after adjustment for FFM measured by five body-composition models: dual-photon X-ray absorptiometry (DXA), hydrodensitometry, total body water, a three-compartment model, a four-compartment model, as well as for the absolute total-body potassium content as a measure of metabolically active FFM. By each analysis, the black women had significantly lower (P < 0.01) FFM-adjusted RMR than the white women; this difference ranged from 671 to 889 kJ/d depending on the body-composition method used to estimate FFM. This could contribute to the difference in the prevalence of obesity in the populations represented by these groups.