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The impact of the poloidally inhomogeneous particle source on the onset of Stringer spin-up (SSU) and geodesic acoustic mode (GAM) is investigated. Using a gyrofluid model with Hammet–Perkins closure, it was found that Landau damping stabilizes both waves and subsequently makes a threshold. To capture the full effects of Landau damping, a gyrokinetic model is adopted and results are compared with those from the gyrofluid model. Both models predicted the same value of the threshold for SSU, while for the case of GAM, the gyrofluid model overestimates the threshold value. Considering maximal throughput of the ITER pellet fueling system, the source intensity is calculated at a similar or slightly lower level compared to the source threshold for SSU. [ABSTRACT FROM AUTHOR]

A study is made of the effect of plasma elongation (κ) on parity of a global electromagnetic (EM) ion temperature gradient mode and intrinsic rotation generation. An odd parity component of the mode is generated by global EM effects and increases with β (=plasma thermal energy/magnetic energy), enhancing the symmetry breaking and subsequent Reynolds stress [Kaang et al., Phys. Plasmas 25, 012505 (2018)]. The plasma elongation is shown to diminish the parity change via the reduction in the effective ion temperature gradient by a factor α = 1 − E ′ , where E = r (κ − 1) / (κ + 1). A quasi-linear analysis indicates that plasma elongation can weaken the generation of intrinsic torque induced by the global EM effect as a result of the decline of the parity change. [ABSTRACT FROM AUTHOR]

We derive expressions for the gyro-averaging operator that is applicable to electrostatic fluctuations in a spatially inhomogeneous magnetic field. Both low and high wavenumber limits are considered. The gyro-averaging operator for the former case is represented by sums of Bessel functions with different orders. A simplified expression is provided as a Padé approximant in the low wavenumber limit. This form could be used in practical computations based on the gyrofluid formulation. In the high wavenumber limit, we find that the operator naturally involves fractional derivatives whose physical interpretations are yet to be explored. Discussions are made of a potential impact of this asymptotic expression in the high wavenumber limit. [ABSTRACT FROM AUTHOR]

X-ray photoelectron spectroscopy and resonant x-ray emission spectroscopy measurements of pellet and thin film forms of TiO2 with implanted Fe ions are presented and discussed. The findings indicate that Fe-implantation in a TiO2 pellet sample induces heterovalent cation substitution (Fe2+→Ti4+) beneath the surface region. But in thin film samples, the clustering of Fe atoms is primarily detected. In addition to this, significant amounts of secondary phases of Fe3+ are detected on the surface of all doped samples due to oxygen exposure. These experimental findings are compared with density functional theory calculations of formation energies for different configurations of structural defects in the implanted TiO2:Fe system. According to our calculations, the clustering of Fe-atoms in TiO2:Fe thin films can be attributed to the formation of combined substitutional and interstitial defects. Further, the differences due to Fe doping in pellet and thin film samples can ultimately be attributed to different surface to volume ratios. [ABSTRACT FROM AUTHOR]

We investigate the finite Larmor radius (FLR) effects that are associated with an external heat source or a sink in the full-f formulation of plasma dynamics. Specifically, we show that a gyrocenter or an additional vorticity source due to the FLR effect should be replenished in fullf turbulence simulations. A quantitative energetics analysis in particle phase space demonstrates that an additional vorticity source is required to satisfy the total energy conservation. A physics picture is presented to elucidate the mechanism of the vorticity source generation from the FLR effects of a heat source or a sink, which reproduces the main result obtained from the quantitative analysis. The additional vorticity source is expected to considerably enhance the generation of the radial electric field and subsequent E × B flow shear in the off-axis heating case. [ABSTRACT FROM AUTHOR]

We develop a conservative gyrofluid model that is suitable for global flux-driven simulations of electrostatic tokamak plasma turbulence. On the basis of the general gyrofluid moment equations, we derive energy equations which enable us to manipulate the impact of a gyrofluid closure on energetics. We demonstrate that an artificial manipulation of high order moment contributions to gyrofluid moment equations via a closure model can lead to the violation of the energy conservation. A fluid closure is also found to restrict the maximum attainable order of finite Larmor radius terms, implying the loss of dynamical information by the closure. [ABSTRACT FROM AUTHOR]

From nonlinear flux-driven fluid simulations, we show that the external torque has a profound influence on ion thermal confinement. A key parameter controlling the confinement change is found to be the ratio of the net external torque to the applied power input. For a given value of external torque, the ion temperature profile destiffening and the corresponding confinement enhancement occur when the ratio is below a threshold value. This confinement improvement is shown to originate from the increase in the zonal flow shearing rate due to the conversion of parallel flow compressibility to zonal vorticity. Confinement degradation and the restoration of profile stiffness arise beyond the critical value of the ratio due to the onset of the parallel velocity gradient instability. This result implies the existence of an optimal torque value for the given heating power to maximize the thermal confinement. [ABSTRACT FROM AUTHOR]

ZnO nanowire field-effect transistors having an omega-shaped floating gate (OSFG) have been successfully fabricated by directly coating CdTe nanocrystals (∼6±2.5 nm) at room temperature, and compared to simultaneously prepared control devices without nanocrystals. Herein, we demonstrate that channel punchthrough may occur when the depletion from the OSFG takes place due to the trapped charges in the nanocrystals. Electrical measurements on the OSFG nanowire devices showed static-induction transistorlike behavior in the drain output IDS-VDS characteristics and a hysteresis window as large as ∼3.1 V in the gate transfer IDS-VGS characteristics. This behavior is ascribed to the presence of the CdTe nanocrystals, and is indicative of the trapping and emission of electrons in the nanocrystals. The numerical simulations clearly show qualitatively the same characteristics as the experimental data and confirm the effect, showing that the change in the potential distribution across the channel, induced by both the wrapping-around gate and the drain, affects the transport characteristics of the device. The cross-sectional energy band and potential profile of the OSFG channel corresponding to the “programed (noncharged)” and “erased (charged)” operations for the device are also discussed on the basis of the numerical capacitance-voltage simulations. [ABSTRACT FROM AUTHOR]

The atomic structure of Al layer on Si(001)-(2×1) surface has been studied by coaxial impact collision ion scattering spectroscopy. When 0.5 monolayer (ML) of Al atoms are adsorbed on Si(001) at room temperature, it is found that Al adatoms are dimerized and Al ad-dimers are oriented parallel to the underlying Si dimers at the position of centering T3 site with a height of 1.02 Å from the first layer of Si(001). The bond length of the Al dimer is 2.67 Å. With increasing Al coverage up to one ML, Al ad-dimers still occupied near T3 site and the next favorable site is near HH site. [ABSTRACT FROM AUTHOR]

The atomic structure of reconstructed Si(001)c(4×4)-C surface has been studied by coaxial impact collision ion scattering spectroscopy. When the 100L of ethylene (C2H4) molecules have been exposed on Si(001)-(2×1) surface at 700 °C, it is found that C atoms cause the ordering of missing Si dimer defects and occupy the fourth layer of Si(001) directly below the bridge site. Our results provide the support for the previous model in which a missing dimer structure is accompanied by C incorporation into the subsurface. [ABSTRACT FROM AUTHOR]

Using a statistical correlation analysis, we compute the evolution of the magnetic Kubo number during an edge pedestal collapse in nonlinear reduced magnetohydrodynamic simulations. The Kubo number is found not to exceed the unity in spite of performing the simulation with a highly unstable initial pressure profile in the ideal ballooning mode. During the edge pedestal collapse, the Kubo number is within the values of 0.2 and 0.6 suggesting that the quasilinear diffusion model is sufficient to explain the energy loss mechanism during the pedestal collapse. Temporal evolution of poloidal correlation lengths of pressure fluctuations resembles with that of the Chirikov parameter and the Kubo number, while radial correlation lengths of the pressure fluctuations are strongly correlated with the radial width of the magnetic stochastic layer. [ABSTRACT FROM AUTHOR]

An approach for printing micron-scale electronic devices built from two-dimensional materials is presented. Experimental phage display techniques and computational atomistic simulation approaches were used to identify a peptide molecule that effectively anchors the basal plane surface of two-dimensional (2D) MoS2 to SiO2 surfaces. This peptide was suspended in water to develop an ink suitable for aerosol jet printing. The printed substrates were then dip coated with a suspension of liquid phase exfoliated 2D MoS2 particles. Strong adhesion of physically continuous lines of these particles was observed only on regions of the substrate patterned with the peptide-based ink, thereby enabling aerosol jet printing as a template for devices based on 2D materials. Graphene was also bound to SiO2 via a similar approach, but with a different peptide known from prior work to selectively adhere to the basal plane of graphene. Fundamental peptide-surface interactions for MoS2, graphene, and SiO2 were explored via simulation and experiment. This printing method is proposed as a route towards large-scale, low temperature patterning of 2D materials and devices. The electrical properties of continuous lines of MoS2 particles printed in a single pass of peptide ink printing were measured via transmission line measurements. The results indicate that this molecular attachment approach to printing possesses several advantages such as overcoming nozzle clogging due to nanomaterial aggregation, decoupling of particle size from any dimensions associated with the printer, and single-pass printing of electrically continuous films. [ABSTRACT FROM AUTHOR]

We report the enhancement of ferroelectric properties in vanadium-doped Bi[sub 4]Ti[sub 3]O[sub 12] (BIT) thin films deposited by a sol-gel method. Compared to the undoped BIT, V-doped BIT (BTV) showed higher polarizations and a better fatigue resistance as reported in ceramic systems recently [Noguchi et al., Appl. Phys. Lett. 78, 1903 (2001)]. BTV showed a remanent polarization (2P[sub r]) of 15.9 µC/cm², higher than the value for BIT, 12.5 µC/cm². The polarization of the BTV thin film capacitor decreased by 19%, while that of the BIT decreased by 23% after the fatigue test with 4 × 10[sup 10] switching cycles. [ABSTRACT FROM AUTHOR]

From the nonlinear simulations of the two-dimensional forced-damped Hasegawa-Mima equation, we show that a Reynolds number-like parameter, Rew, can represent a power law exponent of the energy spectrum in Hasegawa-Mima turbulence. Rew is defined as the ratio of nonlinear convection to dissipation. For a same value of Rew, the power law exponent in the inertial range is shown to be uniquely determined regardless of the forcing and dissipation conditions. At high Rew, the power law exponent asymptotically converges to -7.2, consistent with a recent theoretical prediction based on the shell model [Gürcan et al., Plasma Phys. Controlled Fusion 52, 045002 (2010)]. [ABSTRACT FROM AUTHOR]

A study is conducted on the impact of plasma compressibility on the stability of drift ballooning modes. The two-fluid and four-field model developed by Hazeltine et al. [Phys. Fluids 28, 2466 (1985)] is employed in this study. Results of linear numerical simulations show that finite compressibility destabilizes ballooning modes which are otherwise stable due to the ion diamagnetic drift effect. A systematic study reveals that the parallel compressibility originating from the two-fluid effect, rather than the drift-acoustic wave coupling suggested by Hastie et al. [Phys. Plasmas 10, 4405 (2003)], plays the most important role in destabilizing the ballooning modes. An analytic evaluation of the dispersion relation underpins the strong sensitivity of this parallel compressibility term in the ballooning mode stability. The potential impact of this new understanding on the physics of small edge localized modes is discussed. [ABSTRACT FROM AUTHOR]

Focuses on a study which observed the precipitation of metal silicides in Czochralski silicon crystals contaminated with 3d transition metals. Background on 3d transition-metal silicides; Preparation of the crystals; Description of the crystal's growth.

Studies the effect of sputtering condition on the dynamic characteristics and microstructures of magneto-optical silicon nitride (SiN)/TbFeCo/SiN/aluminum disks for recording media. Reasons for the attention given to transition-metal-rich terbium-iron-cobalt (Tb-Fe-Co) amorphous thin film alloys; Influence of the sputtering parameters of the magneto-optical layer on the static magnetic properties of Tb-Fe-Co; Analysis of the chemical composition of the magneto-optical films.

Numerical studies are made of the effects of resistivity on linear plasma responses to resonant magnetic perturbations (RMPs) in tokamaks based on a reduced magnetohydrodynamic model. From a local two-field model, it is suggested that the ratio of the poloidal electron advection to the resistivity diffusion rate αmαm can be a figure of merit parameter in linear RMP penetration physics. The shielding efficiency is governed by αm, and when αm ≳ 1, RMPs are effectively shielded. Global simulations using a four-field model [Hazeltine and Meiss, Phys. Rep. 121, 1 (1985)] show that there exists an effective threshold of the perpendicular electron flow (Ve,⊥c) beyond which RMPs cannot penetrate. Resistivity is found to determine Ve,⊥c which increases as resistivity becomes higher, making RMP penetration easier. At low resistivity, small Ve,⊥c renders the RMP penetration sensitive to ion collisionality and the change in q 95. The kink response is observed to be closely related to the residual level of RMPs at rational surfaces and can be also strongly affected by resistivity. [ABSTRACT FROM AUTHOR]

Steep pedestal profiles of ion temperature (Ti) and toroidal rotation (V/Φ) are routinely observed in neutral beam injection (NBI)-heated KSTAR H-mode plasmas [W. H. Ko et al., Nucl. Fusion 55, 083013 (2015)]. In this work, we report a result of detailed analysis of pedestal characteristics. By analyzing a set of data with different experimental conditions, we show that Ti and V/Φ pedestals are coupled to each other and correlation between them becomes stronger when NBI-torque is lower. This suggests the existence of intrinsic toroidal torque in the pedestal. Based on a 1D transport analysis, we find that the prevalence of residual micro-turbulences is necessary to explain momentum transport in the pedestal. The estimated strength of intrinsic torque is shown to be comparable to that from a 2.7 MW NBI source. Finally, we show that non-diffusive momentum flux is indispensable to explain momentum transport in the pedestal, and a residual stress model fits the observed momentum flux reasonably. [ABSTRACT FROM AUTHOR]

A study is conducted on the impact of electromagnetic (EM) fluctuations on residual Reynolds stress in the context of the quasi-linear theory. We employ a fluid formulation describing EM ion temperature gradient turbulence. Analyses show that finite plasma β (=plasma thermal energy/magnetic energy) significantly increases the residual stress, potentially leading to the strong enhancement of flow generation in high β plasmas. We identify that this strong increase of residual stress originates from the reinforcement of radial (kǁ) (=spectrally averaged parallel wavenumber) asymmetry due to the deformation of eigenfunctions near a rational surface. [ABSTRACT FROM AUTHOR]

Nonlinear two-fluid and gyrofluid simulations show that an edge localized modes (ELM) crash has two phases: fast initial crash of ion temperature perturbation on the Alfvén time scale and slow turbulence spreading. The turbulence transport phase is a slow encroachment of electron temperature perturbation due to the ELM event into pedestal region. Because of the inward turbulence spreading effect, the energy loss of an ELM decreases when density pedestal height increases. The Landau resonance yields the different cross phase-shift of ions and electrons. A 3 + 1 gyro-Landau-fluid model is implemented in BOUT++ framework. The gyrofluid simulations show that the kinetic effects have stabilizing effects on the ideal ballooning mode and the energy loss increases with the pedestal height. [ABSTRACT FROM AUTHOR]

Using three-dimensional nonlinear simulations of tokamak turbulence, we show that an edge transport barrier (ETB) forms naturally once input power exceeds a threshold value. Profiles, turbulence-driven flows, and neoclassical coefficients are evolved self-consistently. A slow power ramp-up simulation shows that ETB transition is triggered by the turbulence-driven flows via an intermediate phase which involves coherent oscillation of turbulence intensity and E×B flow shear. A novel observation of the evolution is that the turbulence collapses and the ETB transition begins when RT > 1 at t = tR (RT: normalized Reynolds power), while the conventional transition criterion (ωE×B>γlin where ωE×B denotes mean flow shear) is satisfied only after t = tC (>tR), when the mean flow shear grows due to positive feedback. [ABSTRACT FROM AUTHOR]

This paper reports on the theoretical and simulation results of a gyro-Landau-fluid extension of the BOUT++ code, which contributes to increasing the physics understanding of edge-localized-modes (ELMs). Large ELMs with low-to-intermediate-n peeling-ballooning (P-B) modes are significantly suppressed due to finite Larmor radius (FLR) effects when the ion temperature increases. For type-I ELMs, it is found from linear simulations that retaining complete first order FLR corrections as resulting from the incomplete 'gyroviscous cancellation' in Braginskii's two-fluid model is necessary to obtain good agreement with gyro-fluid results for high ion temperature cases (Ti≽3 keV) when the ion density has a strong radial variation, which goes beyond the simple local model of ion diamagnetic stabilization of ideal ballooning modes. The maximum growth rate is inversely proportional to Ti because the FLR effect is proportional to Ti. The FLR effect is also proportional to toroidal mode number n, so for high n cases, the P-B mode is stabilized by FLR effects. Nonlinear gyro-fluid simulations show results that are similar to those from the two-fluid model, namely that the P-B modes trigger magnetic reconnection, which drives the collapse of the pedestal pressure. Due to the additional FLR-corrected nonlinear E × B convection of the ion gyro-center density, for a ballooning-dominated equilibrium the gyro-fluid model further limits the radial spreading of ELMs. In six-field two fluid simulations, the parallel thermal diffusivity is found to prevent the ELM encroachment further into core plasmas and therefore leads to steady state L-mode profiles. The simulation results show that most energy is lost via ion channel during an ELM event, followed by particle loss and electron energy loss. Because edge plasmas have significant spatial inhomogeneities and complicated boundary conditions, we have developed a fast non-Fourier method for the computation of Landau-fluid closure terms based on an accurate and tunable approximation. The accuracy and the fast computational scaling of the method have been demonstrated. [ABSTRACT FROM AUTHOR]

We present a statistical analysis of heat transport in stationary enhanced confinement regimes obtained from flux-driven gyrofluid simulations. The probability density functions of heat flux in improved confinement regimes, characterized by the Nusselt number, show significant deviation from Gaussian, with a markedly fat tail, implying the existence of heat avalanches. Two types of avalanching transport are found to be relevant to stationary states, depending on the degree of turbulence suppression. In the weakly suppressed regime, heat avalanches occur in the form of quasi-periodic (QP) heat pulses. Collisional relaxation of zonal flow is likely to be the origin of these QP heat pulses. This phenomenon is similar to transient limit cycle oscillations observed prior to edge pedestal formation in recent experiments. On the other hand, a spectral analysis of heat flux in the strongly suppressed regime shows the emergence of a 1/f (f is the frequency) band, suggesting the presence of self-organized criticality (SOC)-like episodic heat avalanches. This episodic 1/f heat avalanches have a long temporal correlation and constitute the dominant transport process in this regime. [ABSTRACT FROM AUTHOR]

We study the interplay between intrinsic rotation and internal transport barrier (ITB) dynamics through the dynamic change of the parallel Reynolds stress. Global flux-driven gyrofluid simulations are used for this study. In particular, we investigate the role of parallel velocity gradient instability (PVGI) in the ITB formation and the back transition. It is found that the excitation of PVGI is followed by a change in the Reynolds stress which drives a momentum redistribution. This significantly influences E×B shear evolution and subsequent ITB dynamics. Nonlocal interactions among fluctuations are also observed during the PVGI excitation, resulting in turbulence suppression at the ITB. [ABSTRACT FROM AUTHOR]

A simplified two-dimensional Monte Carlo simulation is performed to estimate the charging potential fluctuations caused by strong binary Coulomb interactions between discrete charged particles in nanometer scale trenches. It is found that the discrete charge effect can be an important part of the nanoscale trench research, inducing scattering of ion trajectories in a nanoscale trench by a fluctuating electric field. The effect can enhance the ion deposition on the side walls and disperse the material contact energy of the incident ions, among others. [ABSTRACT FROM AUTHOR]

Thermal stability of Ta films grown on Si(100) was investigated by in situ x-ray scattering and ex situ cross-sectional transmission electron microscopy. As a Ta/Si(100) film was annealed at around 500 °C, a uniform Ta–Si interlayer was formed at the interface. This interlayer acts as a diffusion barrier. The Ta film with the interlayer is thermally stable up to 700 °C. Meanwhile, Ta films directly annealed to above 640 °C exhibit no interlayer formation and transform to randomly nucleated tantalum-silicide phases. Maintaining a uniform interlayer is a critical factor for enhancing thermal stability of Ta/Si(100) films. [ABSTRACT FROM AUTHOR]

A method to control negative ion density in SF6/Ar capacitive discharges with a biased grid is proposed. It is observed that the negative ion density and its ratio to positive ion density are variable in a wide range from 2.8×107 to 4×109 cm-3 and from 0.18 to 0.86, respectively, depending on the grid bias voltage. To investigate the effect of grid bias on negative ion generation, electron energy distribution functions (EEDFs) are measured and rate constants for electron attachment reactions are calculated at various bias voltages. Results are shown that the attachment processes are predominantly governed by the fraction of low energy electrons in the EEDF, which is controllable using the grid bias. [ABSTRACT FROM AUTHOR]

A theoretical study is made of the effects of radio frequency (rf) waves in the range of ion cyclotron frequency on interchange modes in mirror plasmas. A two-fluid cold plasma model including particle collisions is utilized for the investigation. Both the equilibrium ponderomotive force produced by the gradient of rf wave amplitude and the sideband wave coupling mechanism originated from the nonlinear beating between high frequency waves are taken into account. A tractable form of the dispersion relation for the interchange mode is obtained and applied to carrying out a parametric study. Key parameters affecting the stability boundary are identified and the consequences of the parameter variation on the stability boundary change are analyzed near ion cyclotron resonance region. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Pressure and He mixing effects on plasma parameters in electron temperature control using a grid system are investigated. Electron temperature is higher in lower pressure, when the electron temperature is high and not controlled. Electron density can be increased by about three times by decreasing the source gas pressure from 20 to 1 mTorr, and by about two times by He mixing in the temperature controlled region (diffusion region), while the electron density is decreased in the source region. This electron density increase is mainly due to the increase of the high energy electron population, and the measured electron energy distribution functions clearly show this. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The electron energy distribution functions (EEDFs) are measured by a rf compensated Langmuir probe in a solenoidal inductive reactor at various frequencies and at 2 mTorr of argon. The frequency dependence of the electron energy distribution function is clearly observed. The energy diffusion coefficients against the applied frequencies are calculated from the nonlocal heating theory. It is found that the bounce resonance electrons determine the energy diffusion coefficient shape and the electron energy distribution function at the bounce resonance energy in the energy diffusion coefficient begins to flatten. The exact bounce resonance condition in solenoidal inductive discharge is presented. It is reported that the frequency dependence of the EEDFs is mainly due to the electron bounce resonance in a finite-size solenoidal inductive discharge. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Effects of Na nonstoichiometry in (Bi0.5Na0.5+x)TiO3 ceramics were investigated in the range of x=(-5)-(+1) mol % of Na0.5. A rhombohedral perovskite structure was maintained at all compositions with no secondary phases. Grain size decreased with Na nonstoichiometry. Piezoelectric coefficient (d33) increased from 74 pC/N at x=0 up to 91 pC/N at x=-3.5 then dropped with further Na deficiency. Depolarization temperature (Td), on the other hand, decreased from 190 °C at x=0 down to 112 °C at x=-3.5 then increased. Rhombohedral lattice distortion (90-α) decreasing with Na deficiency was a key factor for the variation in d33 and Td. [ABSTRACT FROM AUTHOR]

A study on the dependence of electron energy distribution function (EEDF) on discharge gap size in capacitive rf discharges was conducted. The evolution of the EEDF over a gap size range from 2.5 to 7 cm in 65 mTorr Ar discharges was investigated both experimentally and theoretically. The measured EEDFs exhibited typical bi-Maxwellian forms with low energy electron groups. A significant depletion in the low energy portion of the bi-Maxwellian was found with decreasing gap size. The results show that electron heating by bulk electric fields, which is the main heating process of the low-energy electrons, is greatly enhanced as the gap size decreases, resulting in the abrupt change of the EEDF. The calculated EEDFs based on nonlocal kinetic theory are in good agreement with the experiments. [ABSTRACT FROM AUTHOR]

Zinc oxide thin films were grown on sapphire substrates by metal organic chemical vapor deposition technique. Single crystal films with flat and smooth surfaces were reproducibly obtained, with application of sample bias and O2 inductively coupled plasma (ICP). At the growth condition of 650 °C, 400 W ICP power, -94 V bias voltage and O/Zn ratio of 75, full width at half maximum values of room temperature photoluminescence and high-resolution x-ray diffraction were measured to be 126 meV and 269 arc sec, respectively. It was proposed that application of sample bias provided reactant ions with kinetic energy, which promoted formation of single crystalline films. [ABSTRACT FROM AUTHOR]

Electrical properties of C60 encapsulated peapod are investigated at various temperatures from room temperature down to T=1.8 K. The current behavior induced by the applied gate and source-drain voltage shows that C60 peapods exhibit single-electron transistor properties. Gate-dependent conductance is enhanced at negative gate voltage and is suppressed and oscillate at positive gate voltage. This behavior is ascribed to the modulation of density of states by the insertion of C60s inside a carbon nanotube. [ABSTRACT FROM AUTHOR]

The chemical depth profile of the passive oxides formed on a stainless-steel surface (type 430, Fe–16.3%Cr) in pH 8.4 borate solution was obtained quantitatively by in situ anomalous x-ray reflectivity. The passive film consists of a Cr oxide inner layer and a Fe/Cr oxide outer layer. The absence of Fe oxide underneath Cr oxide indicates that Cr oxide provides the passivity in stainless steel by inhibiting oxygen anion diffusion. The oxide grows by limited metallic cation transfer. The passivity breaks down in transpassive regime due to the oxidation of the Cr oxide to a soluble oxide. [ABSTRACT FROM AUTHOR]

A study is conducted on a magnetic field effect on electron heating in capacitive rf discharges under a collisional regime, where the electron mean collision frequency is much higher than the rf frequency. The evolution of an electron energy distribution function (EEDF) over a magnetic field range of 0–30 G in 300 mTorr Ar discharges is measured and calculated for the investigation. A significant change in the low-energy range of the EEDF is found during the evolution. The observed result reveals the application of the magnetic field to the high-pressure capacitive plasma gives rise to a cooling effect on the low-energy electrons. This is in contrast to the low-pressure case where the magnetic field enhances the low-energy electron heating. The calculated result of the EEDF is in good agreement with the experiment. [ABSTRACT FROM AUTHOR]

We report an experimental demonstration of rotating plasma discharges of diatomic molecular vapor at pressures of a few hundred kPa, i.e., above atmospheric pressure, using circularly polarized microwaves at 2.45 GHz with no external magnetic fields. The active zone of discharges is observed to rotate at frequency of the order of 0.1–20 Hz, which is equivalent to a linear speed of a few cm/s, depending upon the power level, with the same rotation as that of applied circularly polarized microwave fields, regardless of their helicity. The lethargic rotation of the plasma discharges is explained on the basis of ponderomotive force including absorption of the intrinsic angular momentum of the circularly polarized microwaves. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]