A sensitive and selective amperometric glutamate microsensor with fast response time (<; 5 s) was developed by fabricating a ferrocene/ glutamate oxidase/ Nafion/ polypyrrol (Fc/GlutOx/Nf/Ppy) composite on the micromachined platinum (Pt) microelectrode. The ferrocene-bovine serum albumin (Fc-BSA) conjugate was immobilized on the GlutOx/Nf/Ppy composite of the sensor by physical adsorption. The sensor sensitivity of the Fc-modified glutamate sensor was more than two times higher than that of the control sensor (glutamate sensor without Fc). The Fc modified glutamate microsensor was able to detect glutamate with a wide detection range (up to 540 μM) with a low detection limit at 1.35 μM. The sensor selectivity towards glutamate against interferents increased significantly after the modification of Pt microelectrodes with Ppy and Nf. The interferent responses from ascorbic acid (AA) and dopamine (DA) were <;4% of that detected on the bare Pt electrode. No decrease in sensor sensitivity was observed during repetitive operations in 10 days. While the enhancement of the sensing signal by the immobilized Fc has been demonstrated, its mechanism is still under investigation at the present stage; additional fundamental study to further elucidate the mechanism of the improved sensing signal contributed from the immobilized Fc will be focused on these directions: the preferential electrocatalytic activity contributed from the immobilized Fc or the increasing surface area of the transducer extended by the immobilized Fc.

Spatial variation of the velocity field induced by propagation of an interfacial solitary wave (ISW) is one of the most important research themes in marine science. This velocity field together with the vortex within the system can affect marine operations as the ISW propagates in the ocean. The governing equations presently available are modified to model the velocity and vortex, and are used in numerical experiments. This paper presents the results of laboratory experiments and numerical modeling of the velocity field induced by the propagation of an ISW in depression and elevation on a flat bottom. Laboratory observations reveal that the water particle orbits in different water layers have different motion trails due to the effect of the ISW. In addition, the numerical and laboratory experiments show a self-generated vortex above the interface of a depression ISW as it propagates in a stratified two-layer fluid system on a flat bottom. Interestingly, the interface itself may limit the vertical transfer of mass between the upper and bottom layers in a stratified fluid system.

This paper reports a wideband MMIC low noise amplifier using a 50nm L g E-mode InGaAs PHEMT technology. It demonstrates simultaneous 22dB S21 gain and 1.0dB noise figure at 24GHz operation. The MMIC was designed for 18–35GHz bandwidth; however, noise figure is low and gain is appreciable from 4–40GHz. The amplifier survived being separately subjected to high-power bursts (18dBm P in , 60-sec), and elevated temperature burn-in (85°C for 24-hours) to verify its power handling capability and long-term reliability. The overall amplifier performance, yield, and reliability show that this InGaAs PHEMT technology has the requisite figures-of-merits to advance receiver system performance in hostile environments, as well as the increasingly more demanding commercial environment.

A report is presented on 100 nm and 200 nm InAs PHEMTs on an InP substrate with a record f(T) performance. This result was obtained by reducing a parasitic delay associated with the extrinsic gate capacitances of the device, as well as by using an InAs sub-channel to improve carrier transport properties. In particular, a 100 nm InAs PHEMT exhibits excellent performance, such as g(m,max) = 2 S/mm, f(T) = 421 GHz and f(max) = 620 GHz at V-DS = 0.7 V. The device also shows a well-balanced f(T) and f(max) in excess of 400 GHz, even at V-DS = 0.5 V. In addition, the device gains about 70 % improvement in f(T) as L-g shrinks down from 200 to 100 nm. The results obtained in this work should make this technology of great interest to a multiplicity of applications and guide a realistic path in trying to achieve a 1 THz f(T) from III-V HEMTs in the future.

We have successfully demonstrated a three-step recess process to fabricate high performance E-mode planar InGaAs MOSFETs. Our devices feature a composite gate insulator with InP/Al2O3/HfO2. An Lg=35 nm InGaAs MOSFET with EOT = ~ 0.8 nm exhibits VT = 0.17 V, RON = 285 Ohm-μm, DIBL = 135 mV/V and S = 115 mV/dec, as well as a negligible dispersion and hysteresis behavior. Most importantly, our device displays the highest value of gm_max > 2 mS/μm at VDS = 0.5 V in any III-V MOSFETs.

In this Letter, we report on sub-100 nm recessed In0.7Ga0.3As metal-oxide-semiconductor field-effect transistors (MOSFETs) with outstanding logic and high-frequency performance. The device features ex-situ atomic-layer-deposition (ALD) 2-nm Al2O3 layer on a molecular-beam-epitaxy (MBE) 1-nm InP layer and is fabricated through a triple-recess process. An Lg = 60 nm MOSFET exhibits on-resistance (RON) = 220 Ω-μm, subthreshold-swing (S) = 110 mV/decade, and drain-induced-barrier-lowering (DIBL) = 200 mV/V at VDS = 0.5 V, together with enhancement-mode operation. More importantly, this device displays record maximum transconductance (gm_max) = 2000 μs/μm and current-gain cutoff frequency (fT) = 370 GHz at VDS = 0.5 V, in any III-V MOSFET technology.

We report the development of high performance InP high electron mobility transistors (HEMTs) supported with three interconnect metal layers suitable for advanced RF and mixed signal integrated circuits. Depletion and enhancement mode devices with 35 nm gate-lengths are available with fT / fmax of 536/307 GHz and fT/fmax of 550/346 GHz, respectively. The process shows excellent device uniformity, yield, and reliability. The technology was used to demonstrate broadband feedback-linearized amplifiers with 20 dB S21 gain and an OIP3 of 37 dBm at 2 GHz operation, where PDC is only 313 mW.

Increasing the light harvesting efficiency (LHE) of photovoltaic devices is important for improving the conversion efficiency of solar light into electricity. The optical properties of mesoporous TiO2 films for Dye-Sensitized Solar Cells (DSCs) were investigated by varying the size of the particles (20–150 nm). A four–flux optical model was used to describe the light absorption and scattering within the film. Reflectance and transmittance spectra were recorded by a spectrophotometer equipped with an integrating sphere. The wavelength-dependent absorption coefficient k(λ) and scattering coefficient s(λ) were determined for different films. The absorptance G(λ) (absorbed light flux) for films made of different particle sizes and of varying thicknesses can be calculated from these optical parameters. This study helps in improving the optical design of dye-sensitized solar cells.

The internal quantum efficiency (IQE) of commercial ultra high brightness AlGaInP red LED has already reached 90% or higher but the light extraction efficiency was only about 30% to 50%. Through the improvement of surface texturing structure by nano-imprint technology and current spreading by using narrow width ohmic contact metal line, the light extraction efficiency of AlGaInP red LED was significantly improved up to 60%. In AlGaInN LED, the thermal resistance of the LED chip can be reduced by thinning down or totally removing the sapphire substrate and then replacing it by high thermal conductivity materials. Therefore, the performances of high power AlGaInN LED chips were improved in high current density operation condition.

The recent breakthrough in high power GaN LED's efficiency makes the adoption of these tiny solid state light emitting devices into general lighting application earlier than expected before. However, heat management is still an important issue for these white high power GaN LEDs. So far, the most popular driving current for 1mm square die is about 350mA but there is a trend to increase the driving current up to 1A or even higher. In order not to degrade the LED performance at such a high current operation, it is very important to reduce the thermal resistance and keep the junction temperature below 60 degree centigrade. In the past, GaN flip chip, thin GaN LED, or GaN on SiC or GaN substrate are some typical structures used to make high power LEDs with low thermal resistance. However, all of these methods need very complicated chip process or using very expensive substrates and are difficult to meet general lighting dollar per lumen target. In this study, we proposed a cheaper way to make a high power LED die with lower thermal resistance. We will report how we can achieve the thermal resistance of high power GaN LED die less than 1°C/W.

A stable organic molecular radical, 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO), has been electrochemically studied and employed as a new redox mediator in nanocrystalline TiO2 dye-sensitized solar cells (DSCs) when it is doped with nitrosonium tetrafluoroborate (NOBF4). Reasonable photocurrents can be achieved despite of driving force of only 0.2 eV for the TEMPO/TEMPO + system as compared to 0.6 eV for the iodide/triiodide redox system. Judicious selections of a 5 µm photoanode made from TiO 2 mesoscopic particles (60 nm in diameter) and an organic sensitizer with high molar extinction coefficient yield an overall power conversion of 5.0 % under AM 1.5 illumination at 100 mW cm -2 and an incident photon-to-current conversion efficiencies (IPCE) in excess of 50 %.

TiNi alloy thin films, whose properties are very sensitive to the composition, were prepared using a dc sputter deposition technique. Effects of major deposition parameters on the resulting thin film properties were investigated. The atomic percent of Ti was found to increase with increasing working distance or pressure. The deposition rate was found to increase with the dc power but decrease with the working distance and pressure. The activation energy was also determined and compared to that of bulk TiNi alloys.

In this paper, we report a novel Si-B diffusion source for p(+)-polySi gate p-metal oxide-semiconductor field effect transistors (pMOSFETs). It is found that boron penetration can br effectively suppressed using this process. All the electrical properties of the MOS capacitors are significantly improved over the conventional BF2+ or B+-implanted samples. This process is very promising for fabrication of future surface-channel p-MOSFETs. (C) 1999 The Electrochemical Society. S0013-4651(99)03-017-7. All rights reserved.

The authors report a novel Si-B diffusion source for doping p+-poly-Si gates in pMOSFETs. It is found that B penetration can be effectively suppressed by using this novel process. All of the electrical properties of the MOS capacitors are significantly improved over those in the conventional BF2+ or B+-implanted samples. This new process is very promising for future surface-channel pMOSFETs.