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A synthetic electron cyclotron emission (ECE) diagnostic is used to interpret ECE signals from preset plasma equilibrium profiles, including magnetic field, electron density, and electron temperature. According to the simulation results, the electron temperature (Te) profile covering the harmonic overlap region can be obtained by receiving ECE signals at the high field side (HFS) of the HL-2M plasma. The third harmonic ECE at the low field side (LFS) cannot pass through the second harmonic resonance layer at the HFS unless the optical thickness (τ) of the second harmonic becomes gray (τ ≤ 2). In addition, the impact of the relativistic frequency down-shift has been evaluated and corrected. The measurable range of the HFS ECE has been calculated by scanning different parameters (electron density, temperature, and magnetic field). Higher plasma parameters allow a wider radial range of electron temperature measurements. The minimum inner measurable position can reach R = 120 cm (r/a = −0.89) when the product of core temperature (Te0) and density (ne0) is greater than 35 × 1019 keV m−3, which is extended by more than 30 cm inward compared with that of the LFS measurement. The HFS ECE will greatly improve the diagnostic ability of ECE systems on the HL-2M tokamak. [ABSTRACT FROM AUTHOR]

A phonon-coupled trap model is proposed for trap-assisted injection mechanism in silicon-oxide-nitride-oxide-silicon (SONOS)/metal-nitride-oxide-silicon (MNOS) structures at low voltages. On the basis of this model, a theory of charge injection in SONOS/MNOS has been developed. Charge injection experimental data was fitted by this theory. Obtained trap parameters are close to those previously reported [K. A. Nasyrov et al., J. Appl. Phys. 96, 4293 (2004)], where the current dependence on temperature and electric field was investigated in MNOS. [ABSTRACT FROM AUTHOR]

We report the fabrication, characterization, and field emission properties of (silicon oxide) SiOx coated thin-multiwalled carbon nanotubes (t-MWNTs). The coated t-MWNTs show improved field emission behavior. Initially, raw t-MWNTs (diameter ∼5–8 nm) were functionalized by acid treatment. Using spin on glass as a Si precursor, SiOx was coated on the nanotubes by routine chemical methods. The coated samples were characterized by high resolution transmission electron microscopy (HRTEM), Fourier transform infrared (FTIR) spectroscopy, and thermogravimetric analysis (TGA) techniques. The HRTEM results show that the local thickness of the coating varies from ∼1 to 2 nm. The FTIR investigations show the formation of nanophases, such as Si–C, Si–O–C, and intercalated Si–O, at the coating/nanotube interface. The TGA reveals that the coating prevents the high-temperature oxidation and degradation of the nanotubes. The field emission characteristics of the coated, functionalized, and raw nanotubes show that the turn-on fields and current density are improved for the coated nanotubes. This improvement was attributed to the lowering of the work function and dielectric constant of the C/SiOx interface layer and the localization of the density of states close to the Fermi energy for the coated nanotubes. The analysis of the emission stability spectra shows that the coated nanotubes have a more favorable lifetime. The observed enhancement was attributed to the protection of the nanotubes from the reactive sputter etching during the field emission process. The details of the analysis are presented. [ABSTRACT FROM AUTHOR]

Deep level electron and hole traps were studied by means of deep level transient spectroscopy with electrical and optical injection on a freestanding thick n-GaN sample with low dislocation density. It is shown that at both the upper and the lower surface of the sample there exists a thin, ~0.5 μm layer of damaged material with lowered concentration of electrons and enhanced density of deep centers. Deep in the bulk of the film the densities of the majority of the electron and hole traps are shown to be very low, but measurably higher on the lower face (N face), which was originally closer to the Al[SUB2]O[SUB3] substrate. The two faces are also shown to similarly differ in the density of deep hole traps whose concentration is deduced from low-temperature capacitance-voltage measurements in the dark and after illumination (such traps were previously associated with dislocation states). The concentration of persistent photocapacitance centers is shown to be very low on both sides and considerably lower than previously reported for other n-GaN samples with higher dislocation densities. Electron beam induced current measurements on both sides of the sample reveal the presence of dark spots whose density roughly correlates with the density of dislocations at the upper and lower faces. The reverse current at high voltages is shown to be considerably higher on the N face. The possible relationship of the observed phenomena to dislocations is discussed. [ABSTRACT FROM AUTHOR]

To understand why heterogeneity leads to improved ductility in bulk metallic glasses (BMGs), we derived the local elastic moduli and energy barriers for the activation of shear transformation zones (STZs) in homogeneous and heterogeneous BMGs using high-energy x-ray diffraction. In contrast to the homogeneous glass, STZ activation dynamics in the heterogeneous BMG are spatially nonuniform and the activation of STZs with low energy barriers is favored. Using qualitative arguments, we propose that there is an alternative deformation pathway involving multiple shear bands, which makes the material plastically deformable. [ABSTRACT FROM AUTHOR]

We have investigated the humidity and depurination (creating apurinic sites) effects on the electrical conduction in the λ-DNA films at different relative humidities and depurination times. The DNA films were found to follow the polaron hopping model, and the polaron hopping distance turned out to decrease at the higher relative humidity, more water molecules supposedly being adsorbed on the film. The activation energy showed little dependence on the depurination time at the higher relative humidity, whereas at the lower humidity it increased sharply with increasing depurination time. [ABSTRACT FROM AUTHOR]

The benzene ring vibrational motion in poly(phenylenevinylene) has been studied by 1H nuclear magnetic resonance (NMR) measurements. By employing a simple model of the out-of-plane phenylene oscillation giving rise to a change in the dipolar splitting of the 1H NMR line shape, the oscillation angle of the benzene ring was obtained as a function of temperature. [ABSTRACT FROM AUTHOR]

Excited-state charge-carrier dynamics governs the performance of organometal trihalide perovskites (OTPs) and is strongly influenced by the crystal structure. Characterizing the excited-state charge-carrier dynamics in OTPs under high pressure is imperative for providing crucial insights into structure-property relations. Here, we conduct in situ high-pressure femtosecond transient absorption spectroscopy experiments to study the excited-state carrier dynamics of CH3NH3PbBr3 (MAPbBr3) under hydrostatic pressure. The results indicate that compression is an effective approach to modulate the carrier dynamics of MAPbBr3. Across each pressure-induced phase, carrier relaxation, phonon scattering, and Auger recombination present different pressure-dependent properties under compression. Responsiveness is attributed to the pressure-induced variation in the lattice structure, which also changes the electronic band structure. Specifically, simultaneous prolongation of carrier relaxation and Auger recombination is achieved in the ambient phase, which is very valuable for excess energy harvesting. Our discussion provides clues for optimizing the photovoltaic performance of OTPs. [ABSTRACT FROM AUTHOR]

The annealing temperature (TA) dependence of capacitance-voltage (C-V) characteristics has been studied in metal-oxide-semiconductor structures containing Ge nanocrystals (NCs) produced by ion implantation and annealing. These structures are of interest for application as nonvolatile memory and TA is shown to have a strong influence on the C-V hysteresis. This behavior is shown to be correlated with structural changes of the Ge NCs which have been characterized by synchrotron-radiation photoemission spectroscopy. Specifically, well-defined C-V characteristics with large hysteresis were found only for annealing temperatures greater than 950 °C where Ge nanocrystals are known to form. In this temperature regime, transmission electron microcopy and energy dispersive x-ray spectroscopy demonstrate the existence of regularly arranged Ge NCs of approximately 3–5 nm diameter located around 6.7 nm from the interface. [ABSTRACT FROM AUTHOR]

By applying a critical bias field instead of conventional surface treatments, the electron emission properties of screen-printed nanotubes were investigated through scanning electron microscopy and emission current-voltage characteristics. After the surface treatment, at the bias field of 2.5 V/μm, the electron emission current density with good uniform emission sites reached the value of 2.13 mA/cm2, which was 400 times higher than that of the untreated sample, and the turn-on voltage decreased markedly from 700 to 460 V. In addition, the enhancement of the alignment of carbon nanotubes to the vertical direction was observed, resulting in an increase in the field-enhancement factor. [ABSTRACT FROM AUTHOR]

Microcathodolumunescence (MCL) spectra measurements, MCL and electron beam induced current (EBIC) imaging of the freestanding n-GaN samples grown by hydride vapor phase epitaxy were made. Dark-spot defects in plan-view EBIC and MCL images and dark line defects in MCL images taken on the cleaved surface of the samples could be associated with dislocations. MCL spectra measurements in the vicinity of dislocations and in the matrix do not reveal specific luminescence bands that could be attributed to dislocations but rather suggest that dislocation regions have higher density of deep nonradiative traps. [ABSTRACT FROM AUTHOR]

Spin information carried by magnons is attractive for computing technology, and the development of magnon-based computing circuits is of great interest. However, magnon transport in insulators has been challenging, different from the clear physical picture for spin transport in conductors. Here, we investigate the lateral transport properties of thermally excited magnons in yttrium iron garnet (YIG), a model magnetic insulator. Polarity reversals of detected spins in non-local geometry devices have been experimentally observed and are strongly dependent on temperature, YIG film thickness, and injector-detector separation distance. A competing two-channel transport model for thermally excited magnons is proposed, which is qualitatively consistent with the spin signal behavior. In addition to the fundamental significance for thermal magnon transport, our work furthers the development of magnonics by creating an easily accessible magnon source with controllable transport. [ABSTRACT FROM AUTHOR]

A new plasma/catalyst continuously regenerative hybrid system (PCRHS) is introduced to reduce diesel particulate matter (DPM), NOx, CO, etc., contained in diesel exhaust gas. The catalyst temperature, plasma energy density, and exhaust gas characteristics were investigated with a passenger diesel car (2500cc) at the dynamometer test bed and chassis dynamometer with CVS-75 test mode. It was reported that the smoke removal efficiency was around 70% at the dynamometer test bed with 80 W energy consumption, and that PM removal efficiency was 68% at the chassis dynamometer. The NOx was reduced up to 20% according to the electrode types and temperature, respectively. The hybrid system test shows that DPM and CO were almost removed and NOx reduced to 30% simultaneously by the system. Considering these results, PCRHS could be a promising method to regenerate diesel particulate. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The amphoteric nature of Si/SiO2 interface states in submicron sized metal-oxide-silicon-field-effect-transistors is observed using an enhanced spectroscopic charge pumping method. The method's simplicity and high sensitivity makes it a powerful tool for interrogating the true nature of electrically measured interface states in samples which exhibit extremely low defect densities. The spectroscopic results obtained clearly illustrate a signature 'double peak' density of states consistent with amphoteric Pb center data obtained from electron spin resonance measurements. Since the method is a hybrid of the commonly used charge pumping methodology, it should find widespread use in electronic device characterization. [ABSTRACT FROM AUTHOR]

Systematic investigations on the microstructural evolution of a bimodal eutectic (Ti70.5Fe29.5)91Sn9 ultrafine composite containing Ti3Sn dendrites upon compression reveal that local deformation of the dendrites dominates the early stage of deformation with a plastic strain of [variant_greek_epsilon]p=5.8%. After further deformation ([variant_greek_epsilon]p=10.2%), a wavy propagation of shear bands indicative of dissipation of the shear stress is caused by a rotation of the coarse eutectic structure along the interfaces of the bimodal eutectic structure. [ABSTRACT FROM AUTHOR]

Microstructural investigations on a series of (Ti70.5Fe29.5)100-xSnx alloys with x=5, 7, and 9 reveal that Sn addition is effective in introducing both structural and spatial heterogeneities in ultrafine eutectic composites stemming from a large temperature difference between two eutectic temperatures upon solidification. The microstructural heterogeneities in these ultrafine eutectic composites strongly enhance the room temperature compressive plasticity up to ∼15.7%. [ABSTRACT FROM AUTHOR]

The surface morphology of screen-printed carbon nanotube films was modified by using the poly-dimethylsiloxane (PDMS) elastomer. The entangled carbon nanotube (CNT) bundles were broken up into individual free standing nanotubes to remarkably improve the field-emission characteristics over the as-deposited CNT film. In addition, the cathode film morphology of top-gated triode structures can be treated by using the proposed surface treatment technique, which is a low-cost process. [ABSTRACT FROM AUTHOR]

Metal-oxide-semiconductor structures containing Ge nanocrystals (NCs) of 3–4 nm diameter and 2×1012 cm-2 density are shown to exhibit capacitance-voltage hysteresis of 20.9 V, one of the largest observed in Ge-NC based nonvolatile memories. The Ge NCs were fabricated in an oxide of 30 nm thickness by ion implantation with 30 keV Ge2- ions to an equivalent fluence of 1×1016 Ge cm-2 followed by annealing at 950 °C for 10 min. Secondary ion mass spectroscopy and transmission electron microscopy demonstrate the existence of Ge NCs whose average distance from the SiO2/Si interface is about 6.7 nm. It is shown that the memory effect is a likely consequence of charge trapping at Ge NCs and that it is enhanced by accurately controlling the distribution of Ge NCs with respect to the Si/SiO2 interface. [ABSTRACT FROM AUTHOR]

This letter reports that electromigration lifetimes of Al–2Cu (wt. %) thin-film conducting lines increase by more than three times when the lines are optimally aged to facilitate finely dispersed Al[sub 2]Cu precipitates in the interior of the grains. In contrast to other studies which did not report a beneficial aging effect for Al–Cu films, the present work substantiates the fact that proper control of Al[sub 2]Cu precipitates improves resistance to electromigration failure. However, the benefit of aging the Al-2Cu lines investigated here was less pronounced and confined to a more narrow heat-treatment “window” than that previously found for the Al–2Cu–1Si lines. © 1998 American Institute of Physics. [ABSTRACT FROM AUTHOR]