PM and $hbox{NO}_{rm x}$ Removal for Diesel Engine Emission Using Ozonizer and Chemical Hybrid Reactor

Over the years, we have investigated particulate matter (PM) and $ hbox{NO}_{rm x}$ reduction using nonthermal plasma-chemical hybrid processes without using catalysts. Among nonthermal plasma hybrid processes, the ozonizer combined with the chemical hybrid reactor was investigated using a 479 cc (5.5 kW) power generation diesel engine. The PM deposited on the diesel particulate filter can be incinerated by ozone and $hbox{NO}_{2}$ in a wide range of flue gas temperature. The NO was oxidized to form $hbox{NO}_{2}$ by ozone, and $hbox{NO}_{2}$ was reduced by the 3% $hbox{Na}_{2}hbox{SO}_{3}$ chemical reactor. As the results, PM deposited on both metal and ceramic filters were successfully removed even at ambient temperature. The rate of PM incineration depends on the amount of ozone injected and was significantly higher than the rate of PM generation. Using 2.4% ozone concentration with a flow rate of 10 L/min, 82% of NO having 720 L/min was oxidized to $hbox{NO}_{2}$, and 78% of $ hbox{NO}_{rm x}$ was removed as a chemical scrubber. However, $ hbox{NO}_{rm x}$ removal was deteriorated about 10% after 1-h operation. This was attributed to $hbox{Na}_{2}hbox{SO}_{3}$ oxidation by air, which was evidenced by the reduction of pH in the chemical reactor.      

$hbox{NO}_{rm x}$ Aftertreatment Using Thermal Desorption and Nitrogen Nonthermal Plasma Reduction

In this paper, the results of two experiments are reported. First, the performances of various types of nonthermal plasma reactors for $hbox{NO}_{rm x}$ reduction were compared. It was shown that the surface-discharge reactors have as high $ hbox{NO}_{rm x}$ reduction capabilities as pulse-powered wire–cylinder reactors. Second, $hbox{NO}_{rm x}$ treatment using the surface-discharge reactor with a NO-adsorbent zeolite 13X was performed. Thermal desorption was employed for the regeneration of the zeolite. The $hbox{NO}_{rm x}$ of 350 ppm was kept lower than 18 ppm for at least 11 h, whereas it degraded to 75 ppm in the absence of the regeneration. The result suggested the possibility of an aftertreatment system that employed thermal desorption by utilizing the waste heat of diesel engine exhaust and $hbox{NO}_{rm x}$ reduction by using a surface-discharge reactor.      

Formation of Hydrogen Peroxide, Hydrogen, and Oxygen in Gliding Arc Electrical Discharge Reactors With Water Spray

Formation rates of hydrogen peroxide $(hbox{H}_{2}hbox{O}_{2})$ , hydrogen $(hbox{H}_{2})$, and oxygen $(hbox{O}_{2})$ in gliding arc discharge with water spray and a variety of carrier gases, including Ar, He, $hbox{O}_{2}$, $hbox{N}_{2}$, and $ hbox{CO}_{2}$, were determined. Significantly larger rates and concentrations of hydrogen peroxide were found in the present reactor with a modified liquid injection nozzle than in previous work. As long as nitrogen oxide species are minimized or not formed, the formation rates of hydrogen peroxide were less sensitive to the carrier gas ($hbox{O}_{2}$, $ hbox{CO}_{2}$, Ar), although He gave about one-half the rate as these other gases. The stoichiometric ratios of $hbox{H}_{2}: hbox{O}_{2}: hbox{H}_{2}hbox{O}_{2}$ exhibited a range of behaviors for the different carrier gases with the highest $hbox{H}_{2}$ formation rate in Ar and $hbox{N}_{2}$ and the largest $hbox{O}_{2}$ formation in $hbox{CO}_{2}$.      

Time-Dependent Dielectric Breakdown of 4H-SiC/$ hbox{SiO}_{2}$ MOS Capacitors

Time-dependent dielectric breakdown (TDDB) is one of the major issues concerning long-range reliability of dielectric layers in SiC-based high-power devices. Despite the extensive research on TDDB of $hbox{SiO}_{2}$ layers on Si, there is a lack of high-quality statistical TDDB data of $hbox{SiO}_{2}$ layers on SiC. This paper presents comprehensive TDDB data of 4H-SiC capacitors with a $ hbox{SiO}_{2}$ gate insulator collected over a wide range of electric fields and temperatures. The results show that at low fields, the electric field acceleration parameter is between 2.07 and 3.22 cm/MV. At fields higher than 8.5 MV/cm, the electric field acceleration parameter is about 4.6 cm/MV, indicating a different failure mechanism under high electric field stress. Thus, lifetime extrapolation must be based on failure data collected below 8.5 MV/cm. Temperature acceleration follows the Arrhenius model with activation energy of about 1 eV, similar to thick $hbox{SiO}_{2}$ layers on Si. Based on these experimental data, we propose an accurate model for lifetime assessment of 4H-SiC MOS devices considering electric field and temperature acceleration, area, and failure rate percentile scaling. It is also demonstrated that temperatures as high as 365 $^{circ}hbox{C}$ can be used to accelerate TDDB of SiC devices at the wafer level.      

Channel Hot-Carrier Degradation in Short-Channel Transistors With High- $k$/Metal Gate Stacks

Channel hot-carrier (CHC) degradation in nMOS transistors is studied for different $hbox{SiO}_{2}/hbox{HfSiON}$ dielectric stacks and compared to $hbox{SiO}_{2}$. We show that, independent of the gate dielectric, in short-channel transistors, the substrate current peak (used as a measure for the highest degradation) is at $V_{G} = V_{D}$, whereas for longer channels, the maximum peak is near $V_{G} = V_{D}/hbox{2}$. We demonstrate that this shift in the most damaging CHC condition is not caused by the presence of the high- $k$ layer but by short-channel effects. Furthermore, the CHC lifetime of short-channel transistors was evaluated at the most damaging condition $V_{G} = V_{D}$ , revealing sufficient reliability and even larger operating voltages for the high- $k$ stacks than for the $ hbox{SiO}_{2}$ reference.      

Positive Bias Temperature Instability Effects in nMOSFETs With $hbox{HfO}_{2}/hbox{TiN}$ Gate Stacks

The Positive Bias Temperature Instability (PBTI) and the stress-induced leakage current (SILC) effects are thoroughly examined in nFETs with $hbox{SiO}_{2}/hbox{HfO}_{2}/hbox{TiN}$ dual-layer gate stacks under a wide range of bias and temperature stress conditions. Experimental evidence of the SILC increase with time is obtained suggesting the activation of a trap generation mechanism. Threshold voltage $(V_{rm T})$ instability is found to be the result of a complicated interplay of two separate mechanisms; filling of preexisting electron traps versus trap generation each one dominating at different stress condition regimes. Furthermore, $V_{rm T}$ instability relaxation experiments, undertaken at judiciously chosen conditions, show that the preexisting and stress-induced traps exhibit similar detrapping kinetics indicating that both types of traps may have similar characteristics. Finally, it is shown that the role of the SILC effect (and the associated trap generation component) on $V_{rm T}$ instability is process dependent and that SILC reduction is accompanied by enhancement of the PBTI device lifetime.      

$hbox{1}/f$ Noise Characterization of n- and p-Type Polycrystalline-Silicon Thin-Film Transistors

This paper presents a study of low-frequency-noise properties of n- and p-type polycrystalline-silicon (poly-Si) thin-film transistors (TFTs). The $hbox{1}/f$ noise behavior of these devices prompted the use of the carrier number with correlated mobility fluctuation model for data analysis. From this model, trap densities in this study were found to range from $hbox{3.5} times hbox{10}^{16}$ to $hbox{4} times hbox{10}^{17} hbox{states/eV} cdot hbox{cm}^{3}$, which is indicative of a good top surface of the channel and interface between the oxide and poly-Si. The normalized current noise of the p-channel TFTs changes with the inverse of current, independent of the width $(W)$ -to-length $(L)$ ratio of the channel; the normalized current noise of the n-channel TFTs also changes with the inverse of current, but not independent of the $W/L$ ratio. For smaller currents, noise is caused by traps at or near the oxide/semiconductor interface, whereas for larger currents, the larger contribution to the noise is believed to originate from the bulk.      

High-Power $hbox{Yb}^{{bm 3}{bm +}}$-Doped Phosphate Fiber Amplifier

We report on the development of novel high-power light sources utilizing a $hbox{Yb}^{3+}$-doped phosphate fiber as the gain element. This host presents several key benefits over silica, particularly much higher $hbox{Yb}_{2} hbox{O}_{3}$ concentrations (up to 26 wt%), a 50% weaker stimulated Brillouin scattering (SBS) gain cross section, and the absence of observable photodarkening even at high population inversion. These properties result in a greatly increased SBS threshold compared to silica fibers, and therefore, potentially much higher output powers out of either a multimode large mode area or a single-mode fiber, which means in the latter case a higher beam quality. To quantify these predictions, we show through numerical simulations that double-clad phosphate fibers should produce as much as $sim$700 W of single-frequency output power in a step index, single-mode core. As a step in this direction, we report a short phosphate fiber amplifier doped with 12 wt% $hbox{Yb}_{2} hbox{O}_{3}$ that emits 16 W of single-frequency single-mode output. We also describe a single-mode phosphate fiber laser with a maximum output power of 57 W. The laser slope efficiency is currently limited by the fairly high fiber loss ( $sim$3 dB/m). Measurements indicate that 77% of this loss originates from impurity absorption, and the rest from scattering.      

Characteristics and Reliability of Hafnium Oxide Dielectric Stacks With Room Temperature Grown Interfacial Anodic Oxide

Hafnium oxide dielectric stacks with anodic oxide interfacial layer (ANO-IL) were investigated under low-temperature consideration. A tilted-substrate sputtering technique, which provides various film thicknesses in one processing step, was proposed and useful for the characterization of charge distribution. It was found that charges existed in the $hbox{HfO}_{2}$/ANO-IL were smaller than that in $hbox{HfO}_{2}$/rapid-thermal-oxidation IL. The prepared samples exhibit good electrical characteristics, including small electrical hysteresis ( $≪$10 mV), low leakage current, high effective dielectric breakdown field of 12.7 MV/cm, and maximum operating voltages of ${-}$ 2.74 V at 25 $^{circ}hbox{C}$ and ${-}$2.32 V at 125 $^{circ} hbox{C}$ for $hbox{EOT} = hbox{2.3} hbox{nm}$ stacks under a ten-year lifetime evaluation. The results suggest that the quality of IL in the dielectric stack is a critical reliability issue and that ANO is provided as a candidate for IL consideration of low-temperature dielectric stacks.      

Reliability Challenges for CMOS Technology Qualifications With Hafnium Oxide/Titanium Nitride Gate Stacks

It has been demonstrated that the introduction of $hbox{HfO}_{2}/ hbox{TiN}$ gate stacks into CMOS technologies provides the means to continue with traditional device gate length scaling. However, the introduction of $hbox{HfO}_{2}$ as a new gate dielectric and TiN as a metallic gate electrode into the gate stack of FETs brings about new challenges for understanding reliability physics and qualification. This contribution summarizes recent advances in the understanding of charge trapping and defect generation in $hbox{HfO}_{2}/ hbox{TiN}$ gate stacks. This paper relates the electrical properties to the chemical/physical properties of the high-$varepsilon$ dielectric and discusses test procedures specifically tailored to quantify gate stack reliability of $ hbox{HfO}_{2}/hbox{TiN}$ gate stacks.      

Enhancement of Light Power for Blue InGaN LEDs by Using Low-Indium-Content InGaN Barriers

The optical properties of blue InGaN LEDs that emit in a spectral range from 410 to 445 nm are theoretically investigated by using the APSYS simulation program. It is found that the light performance can be enhanced effectively when the conventional GaN barrier layers are replaced by $hbox{In}_{0.02}hbox{Ga}_{0.98}hbox{N}$ and $hbox{In}_{0.05}hbox{Ga}_{0.95}hbox{N}$ barrier layers. The numerical results indicate that the output power of LEDs with $hbox{In}_{0.02}hbox{Ga}_{0.98} hbox{N}$ barrier layers is improved gradually above the emission wavelength of 410 nm. However, when the $hbox{In}_{0.05}hbox{Ga}_{0.95}hbox{N}$ barrier layers are used, the emitting power of LEDs varies significantly when the emission wavelength changes. When the emission wavelength is 410 nm, the use of GaN and $hbox{In}_{0.02}hbox{Ga}_{0.98}hbox{N}$ barrier layers can lead to higher output power. However, if the emission wavelength is 445 nm, the use of $hbox{In}_{0.05}hbox{Ga}_{0.95}hbox{N}$ barrier layers is beneficial for maintaining high output power.      

Optimization of Light Extraction Efficiency of III-Nitride LEDs With Self-Assembled Colloidal-Based Microlenses

Improvement of light extraction efficiency of InGaN LEDs using colloidal-based ${rm SiO}_{2}$/polystyrene (PS) microlens arrays was demonstrated. The size effect of the ${rm SiO}_{2}$ microspheres and the thickness effect of the PS layer on the light extraction efficiency of III-nitride LEDs were studied. The monolayer rapid convective deposition conditions for ${rm SiO}_{2}$ microspheres were also investigated. Ray tracing simulations show that the use of microlens arrays can lead to increase in light extraction efficiency of InGaN LEDs by 2.64 times. This is consistent with experiments that demonstrated 2.49 times improvement in light extraction utilizing ${rm SiO}_{2}$/PS microlens arrays. The enhancement in light extraction efficiency is attributed to increase in effective photon escape cone due to ${rm SiO}_{2}$/PS microlens arrays, and reduced Fresnel reflection within the photon escape cone due to the grading of refractive index change between GaN/${rm SiO}_{2}$/PS/air interface.      

Highly Stable 1.3-$muhbox{m}$ -Wavelength Lasers With p- and n-InP Buried Heterostructure

Highly stable 1.3-$muhbox{m}$-wavelength Fabry–Perot lasers with a p- and n-type InP buried heterostructure have been achieved at an ambient temperature of 85 $^{circ}hbox{C}$. The $t^{0.5}$ deterioration (second-stage degradation) property does not appear clearly within 6000 h, and the saturated first-stage degradation property remains. It is confirmed that the fabricated 1.3-$muhbox{m}$ FP lasers have a different optical-beam-induced-current characteristic from lasers suffering from $t^{0.5}$ deterioration. The first-stage degradation is due to the deterioration of the active layer and is attributed to the fact that some nonradiative recombination centers are generated in the active layer.      

Solvent Effect on the Electrical Properties of Triisopropylsilylethynyl (TIPS) Pentacene Organic Thin-Film Transistors

We investigated the electrical properties of triisopropylsilylethynyl (TIPS) pentacene organic thin-film transistor (OTFT) depending on solvent type. TIPS pentacene was spin coated by using chlorobenzene, p-xylene, chloroform, and toluene as solvents. A broad spectrum of electrical properties was affected by the solvent choice. Fabricated OTFT with chlorobenzene shows field-effect mobility of $hbox{1.0} times hbox{10}^{-2} hbox{cm}^{2}/hbox{V}cdot hbox{s}$, on/off ratio of $hbox{4.3} times hbox{10}^{3}$, and threshold voltage of 5.5 V. In contrast, with chloroform, the mobility is $hbox{5.8} times hbox{10}^{-7} hbox{cm}^{2}/hbox{V} cdot hbox{s}$, on/off ratio of $hbox{1.1} times hbox{10}^{2}$, and threshold voltage of 1.7 V. Further investigation by measurement of the grain size of TIPS thin films by atomic force microscopy (AFM) and X-ray diffraction spectroscopy showed that solvents with higher boiling points resulted in larger grain sizes and improved crystallinity. The higher performance electrical characteristics are explained by large grain size and high crystallinity of the TIPS pentacene layer in films spin coated with higher boiling point such as chlorobenzene.      

Visible and 1.54 m Emission From Amorphous Silicon Nitride Films by Reactive Cosputtering

In this paper, we present our main results on the structural and optical properties of light-emitting amorphous silicon nitride ($hbox{SiN}_{x}$) films fabricated by reactive magnetron cosputtering. In particular, we discuss the origin of the visible emission in amorphous silicon nitride films and investigate the optical emission properties of Erbium-doped amorphous silicon nitride ( $hbox{Er:SiN}_{x}$). The mechanisms of Er excitation and de-excitation in $hbox{Er:SiN}_{x}$ are discussed in relation to the engineering of efficient light sources at 1.54 $mu$m for on-chip nanophotonics applications. These results suggest that Er-doped amorphous silicon nitride films have a large potential for the fabrication of optically active photonic devices based on the Si technology.      

High-Speed Single-Photon Frequency Upconversion With Synchronous Pump Pulses

Single-photon signals at 1.56 $mu$m were converted into the visible region by sum-frequency generation, with synchronous pump pulses at 1.03 $mu$m in a periodically poled lithium niobate crystal. The signal and pump sources were provided by two synchronized mode-locked fiber lasers at the operation rate of 7.88 MHz. Such a high-speed single-photon upconversion system has shown an overall detection efficiency of 10.4%. The corresponding background noise was measured to be 3.3$,times,$10 $^{3}$ s$^{-1}$. The noise-equivalent power in this scheme was 9.93$,times,$10 $^{-17}$ W/Hz$^{1/2}$, which was the lowest compared to the other upconversion systems with similar pump and signal wavelengths.      

Assessing the Reliability of Elastomer Sockets in Temperature Environments

This paper presents a study on the contact resistance behavior of elastomer sockets used to interconnect microprocessors and printed circuit boards in enterprise servers. The integrated circuit sockets, installed in production representative assemblies, were evaluated at 25 $^{circ}hbox{C}$ , 55 $^{circ}hbox{C}$, and 75 $^{circ}hbox{C}$ for 2000 h. A sample subset was evaluated up to 16 500 h at 25 $^{circ}hbox{C}$ and up to 4500 h at 55 $^{circ}hbox{C}$. The test results show that contact resistance decreases over time for all test conditions, as much as 50% from their initial values. Elastomer contact behavior is strongly dependent on temperature and time. The resistance behavior over temperature is modeled with multiple statistical distributions. The mean contact resistance is represented with a physics-of-failure model, and the elastomer contact reliability is estimated using a log-normal distribution.      

Design Analysis of Staggered InGaN Quantum Wells Light-Emitting Diodes at 500–540 nm

Staggered InGaN quantum wells (QWs) are analyzed as improved active region for light-emitting diodes (LEDs) emitting at 500 nm and 540 nm, respectively. The calculation of band structure is based on a self-consistent 6-band $k{bf cdot}p$ formalism taking into account the valence band mixing, strain effect, and spontaneous and piezoelectric polarizations as well as the carrier screening effect. Both two-layer staggered $hbox{In}_{x}hbox{Ga}_{1-x}hbox{N/}hbox{In}_{y}hbox{Ga}_{1-y}hbox{N}$ QW and three-layer staggered $hbox{In}_{y}hbox{Ga}_{1-y}hbox{N/}hbox{In}_{x}hbox{Ga}_{1-x}hbox{N/}hbox{In}_{y}hbox{Ga}_{1-y}hbox{N}$ QW structures are investigated as active region to enhance the spontaneous emission radiative recombination rate ($R_{rm sp}$) for LEDs emitting at 500 nm and 540 nm. Analysis of the spontaneous emission radiative recombination rate ($R_{rm sp}$ ) shows significant enhancement for both two-layer staggered InGaN QW and three-layer staggered InGaN QW, in comparison to that of the conventional $hbox{In}_{z}hbox{Ga}_{1-z}hbox{N}$ QW. The studies of the carrier lifetime indicate a significant reduction of the carrier lifetime for staggered InGaN QWs, which contribute to the enhancement of the radiative efficiency for both two-layer staggered InGaN QW and three-layer staggered InGaN QW LEDs emitting at 500 nm and 540 nm.      

Thresholds for Transverse Stimulation: Fiber Bundles in a Uniform Field

Cable theory is used to model fibers (neural or muscular) subjected to an extracellular stimulus or activating function along the fiber (longitudinal stimulation). There are cases however, in which activation from fields across a fiber (transverse stimulation) is dominant and the activating function is insufficient to predict the relative stimulus thresholds for cells in a bundle. This work proposes a general method of quantifying transverse extracellular stimulation using ideal cases of long fibers oriented perpendicular to a uniform field (circular cells in a 2-D extracellular domain). Several methods are compared against a fully coupled model to compute electrical potentials around each cell of a bundle and predict the magnitude of applied plate potential $({mitPhi}_{p})$ needed to activate a given cell $({mitPhi}_{rm pact})$. The results show that with transverse stimulation, the effect of cell presence on the external field must be considered to accurately compute ${mitPhi}_{rm pact}$. They also show that approximating cells as holes can accurately predict firing order and ${mitPhi}_{rm pact}$ of cells in bundles. Potential profiles from this hole model can also be applied to single cell models to account for time-dependent transmembrane voltage responses and more accurately predict ${mitPhi}_{rm pact}$. The approaches used herein apply to other examples of transverse cell stimulation where cable theory is inapplicable and coupled model simulation is too costly to compute.      

Numerical and Experimental Analysis of Nanosecond Pulse Dielectric Barrier Discharge-Induced Nonthermal Plasma for Pollution Control

Numerical and experimental analyses are conducted on a nanosecond pulse dielectric barrier discharge-induced nonthermal plasma (NTP) for pollution control. In the numerical analysis, a commercial simulation software, CFD-ACE $+$ solver, is used. The result indicates that a streamer progressing from the positive electrode to the grounded one is well simulated. At the end of the pulse, the electron temperature and electron number density in the coaxial-type plasma reactor finally reach approximately 1.7 eV and $10^{15} hbox{m}^{-3}$, respectively. The radial electric field is almost constant in the plasma region. During the single pulse, the peak concentration of ozone is approximately 40 ppm near the surface of the glass barrier. Next, an experimental analysis on the optical emission spectra of the NTP is carried out. In the result, the second positive bands spectra of $ hbox{N}_{2}$ are observed. The evaluated electron temperature is almost constant (approximately 1.8 eV), irrespective of frequency, discharge power, and radial position. This value and tendency agree well with the numerical results.