Modelling and Optimization for Deposition of SiOxNy Films by Radio-Frequency Reactive Sputtering

SiOxNy films are deposited by reactive sputtering from a Si target in Ar/O2/N2 atmospheres. In order to achieve the control of film composition and to keep a high deposition rate at the same time, a new sputtering model based on Berg＇s work is provided for the condition of double reactive gases. Analysis based on this model shows that the deposition process can easily enter the target-poisoning mode when the preset gas flow （N2 in this work） is too high, and the film composition will change from nitrogen-rich to SiO2-like with the increase of oxygen supply while keeping the N2 supply constant. The modelling results are confirmed in the deposition process of SiOxNy. Target self-bias voltages during sputtering are measured to characterize the different sputtering modes. FTIR-spectra and dielectric measurements are used to testify the model prediction of composition. Finally, an optimized sputtering condition is selected with the O2/N2 flow ratio varying from 0 to I and N2 supply fixed at I sccm. Average deposition rate of 17nm/min is obtained under this selected condition, which has suggested the model validity and potential for industry applications.     

Investigation of muon states in silicon and germanium by field-quenching and RFμSR

The temperature dependence of the three states of positive muons in the semiconductors with diamond structure ( ⁺ in diamagnetic states ^d and paramagnetic muonium Mu and Mu^*) have been investigated on six Si (pure, B and P doped) and four Ge (ultrapure, CZ-grown undoped, Ga and Sb doped) single crystals by longitudinal field-quenching and radio-frequency ⁺SR. Clear evidence for the transition Mu^{* d} is found. The influence of light-induced charge-carriers is shown to be quite different in p- and n-type material.The work has been supported by the Bundesministerium für Forschung und Technologie in Bonn, Germany, under contract no. 03-SE3STU.     

Lactate quantification by means of press spectroscopy—Influence of refocusing pulses and timing scheme

The quantitative assessment of lactic acid in tissue is an important goal for in vivo volume-selective NMR spectroscopy to aid in the noninvasive diagnosis of oxygen deficiency or other metabolic disorders. PRESS localized ¹H spectra provide comparatively high signal-to-noise ratio from small volume elements in a single acquisition mode. The quantification of lactate after multipulse excitation is not trivial due to the J-coupling characteristics which do not occur for the substances serving as references. The influence of the timing scheme and of the quality of the refocusing pulses was systematically evaluated for the lactate resonances by volume-selective measurements. Gaussian pulses, Hanning-filtered sinc pulses, and numerically optimized RE-BURP-pulses were applied for refocusing the magnetization in the PRESS sequence and the effects on the lactate AX₃ spin system were compared. For these pulses, sequence parameters are presented providing high sensitivity to lactate signals. Timing schemes are shown which provide good quantification of lactate, even in cases with B₁-inhomogeneities or slight misadjustment of the transmitter amplitude. The combination of both echo times in the double-echo sequences clearly influences the signal characteristics of lactate at overall echo times near TE = 145 and 290 ms, which may result in pure in-phase magnetization for this weakly coupled homonuclear system. Numerically optimized refocusing pulses (RE-BURP) provided up to 50% higher signal ratio of the methyl protons of lactate to uncoupled nuclei than the often used Hanning-filtered sinc pulses.     

Optimization of High-Order Harmonic by Genetic Algorithm for the Chirp and Phase of Few-Cycle Pulses

The brightness of a particular harmonic order is optimized for the chirp and initial phase of the laser pulse by genetic algorithm. The influences of the chirp and initial phase of the excitation pulse on the harmonic spectra are discussed in terms of the semi-classical model including the propagation effects. The results indicate that the harmonic intensity and cutoff have strong dependence on the chirp of the laser pulse, but slightly on its initial phase. The high-order harmonics can be enhanced by the optimal laser pulse and its cutoff can be tuned by optimization of the chirp and initial phase of the laser pulse.     

Optimizing the performance of TOAD by changing the wavelength and power of control pulse

The performance of terahertz optical asymmetric demultiplexer (TOAD) has been studied by modelling the semiconductor optical amplifier (SOA) in which the intraband effects had been taken into account. Numerical results are coincident with the experiment results. We interpret why there are three peaks in the switching window, which has never been reported before. In addition, we put forward the definition of the flatness of the switching window of TOAD for the first time By analysing the different phase of clockwise and counter clockwise signal pulse changed by SOA, appropriate peak power of control pulse and wavelength of signal and control pulse have been calculated in order to obtain large output power and flat switching window of TOAD.     

Dark and kink soliton solutions of the generalized ZK–BBM equation by iterative scheme

The generalized ZK–BBM equation is solved using iterative scheme of the Adomian decomposition method (ADM) and variational iteration method (VIM). A dark and a kink soliton solutions of the generalized ZK–BBM equation are obtained under initial conditions. The convergence analysis of the ADM and VIM solution shows that these solutions are convergent. The comparison of the ADM and VIM solutions with the exact solution shows that the solutions of the generalized ZK–BBM equation by the iterative methods are almost exact. The absolute errors show that the accuracy and efficiency of the ADM and VIM depend on the problem and its domain. It is found that the iterative scheme of Adomian decomposition method and variational iteration method are quite efficient for the soliton solution of the generalized ZK–BBM equation.     

Fabrication and performance of polymer–nanocomposite anti-reflective thin films deposited by RIR-MAPLE

Design of polymer anti-reflective (AR) optical coatings for plastic substrates is challenging because polymers exhibit a relatively narrow range of refractive indices. Here, we report synthesis of a four-layer AR stack using hybrid polymer:nanoparticle materials deposited by resonant infrared matrix-assisted pulsed laser evaporation. An Er:YAG laser ablated frozen solutions of a high-index composite containing TiO₂ nanoparticles and poly(methyl-methacrylate) (PMMA), alternating with a layer of PMMA. The optimized AR coatings, with thicknesses calculated using commercial software, yielded a coating for polycarbonate with transmission over 97 %, scattering <3 %, and a reflection coefficient below 0.5 % across the visible range, with a much smaller number of layers than would be predicted by a standard thin film calculation. The TiO₂ nanoparticles contribute more to the enhanced refractive index of the high-index layers than can be accounted for by an effective medium model of the nanocomposite.     

Possible generation of π-condensation in a free space by collisions between photons and protons

A sharply peaked structure is found in the angular distribution of emitted π~+ mesons from photon–proton collisions.This offers a possible way to generate a π~+-condensation in free space. To make the stimulated emission of π~+-mesons efficient, a ring resonator is designed.     

Amplification and measurement of single 1.6–3.5 ps Pulses generated by a distributed feedback dye laser

Twenty FIR laser lines with wavelengths between 146 and 2000 m have been observed from deuterated formyl fluoride (DCOF) optically pumped with isotopic CO₂ lasers. Tunable diode laser measurements on thev ₄ band of DCOF were combined with earlier high precision spectroscopic data on thev ₃ andv ₄ bands, and enabled identification of the transitions responsible for 9 of the new FIR lines.     

Structural and optical properties of N-doped β-Ga2O3 films deposited by RF magnetron sputtering

The N-doped β-Ga₂O₃ ?lms were grown on Si and quartz substrates by RF magnetron sputtering in different ammonia partial pressure ratios (from 0% to 30%). The influence of ammonia partial pressure ratios and annealing treatment on the optical and structural properties were studied. The microstructure, optical transmittance, optical absorption and optical energy gap of the N-doped β-Ga₂O₃ films are significantly changed with the increasing of ammonia partial pressure. The green, blue and ultraviolet emission bands are observed and discussed.     

Is it me or not me? Modulation of perceptual-motor awareness and visuomotor performance by mindfulness meditation

ABSTRACT: BACKGROUND: Attribution of agency involves the ability to distinguish our own actions and their sensory consequences which are self-generated from those generated by external agents. There are several pathological cases in which motor awareness is dramatically impaired. On the other hand, awareness-enhancement practices like tai-chi and yoga are shown to improve perceptual-motor awareness. Meditation is known to have positive impacts on perception, attention and consciousness itself, but it is still unclear how meditation changes sensorimotor integration processes and awareness of action. The aim of this study was to investigate how visuomotor performance and self-agency is modulated by mindfulness meditation. This was done by studying meditators' performance during a conflicting reaching task, where the congruency between actions and their consequences is gradually altered. This task was presented to novices in meditation before and after an intensive 8 weeks mindfulness meditation training (MBSR). The data of this sample was compared to a group of long-term meditators and a group of healthy non-meditators. RESULTS: Mindfulness resulted in a significant improvement in motor control during perceptual-motor conflict in both groups. Novices in mindfulness demonstrated a strongly increased sensitivity to detect external perturbation after the MBSR intervention. Both mindfulness groups demonstrated a speed/accuracy trade-off in comparison to their respective controls. This resulted in slower and more accurate movements. CONCLUSIONS: Our results suggest that mindfulness meditation practice is associated with slower body movements which in turn may lead to an increase in monitoring of body states and optimized re-adjustment of movement trajectory, and consequently to better motor performance. This extended conscious monitoring of perceptual and motor cues may explain how, while dealing with perceptual-motor conflict, improvement in motor control goes beyond the mere increase of movement time. The reduction of detection threshold in the MBSR group is also likely due to the enhanced monitoring of these processes. Our findings confirmed our assumptions about the positive effect of mindfulness on perceptual-motor integration processes.     

Electrodeposition of polyaniline–carbon nanotubes composite films and investigation on their role in corrosion protection of austenitic stainless steel by SNIFTIR analysis

Composite films of polyaniline (PANI) and carbon nanotubes (CNTs) were prepared by electrochemical co-deposition from solutions of the corresponding monomer containing two different kinds of CNTs. The first type was commercial (diameter = 110–170 nm, length = 5–9 μm) and the second one was home-made (diameter = 30 nm, length = 5–20 μm). The electrochemical behaviour of PANI–CNTs composite films was investigated with Cyclic Voltammetry and the surface morphology was analysed by Scanning Electron Microscopy (SEM). Subtractively Normalised Interfacial FT-IR procedure was used to investigate the presence of corrosion products when the films were deposited on stainless steel substrates and exposed to acid environment. The spectral investigations were utilised to understand the role of composite films in the corrosion protection and to discriminate the best performance CNTs.     

Judd-Oflet analysis of spectrum and laser performance of Ho：YAP crystal end-pumped by 1.91μm Tm：YLF laser

The Ho:YAP crystal is grown by the Czochralski technique.The room temperature polarized absorption spectra of Ho:YAP crystal was measured on a c cut sample with 1 at% holmium.According to the obtained Judd-Ofelt intensity parameters Ω2 = 1.42 × 10-20 cm2,Ω4 = 2.92 × 10-20 cm2,and Ω6 = 1.71 × 10-20 cm2,this paper calculated the fluorescence lifetime to be 6 ms for 5I7 →5 I8 transition,and the integrated emission cross section to be 2.24×10-18 cm2.It investigates the room temperature Ho:YAP laser end pumped by a 1.91 μm Tm:YLF laser.The maximum output power was 4.1 W when the incident 1.91 μm pump power was 14.4 W.The slope efficiency is 40.8%,corresponding to an optical to optical conversion efficiency of 28.4%.The Ho:YAP output wavelength was centred at 2118 nm with full width at half maximum of about 0.8 nm.     

Production of G(1590) and other mesons decaying into η pairs by 100 GeV/c π− on protons

New data on the scalar G(1590) meson which decays into ηη have been obtained in an experiment at the CERN SPS. η pairs are detected with the electromagnetic calorimeter GAMS both through their decay into 4γ and into 8γ. ϵ(1300), f(1270), f′(1525) as well as the spin-4 h(2030) mesons have also been observed to decay in the same mode. Their branching ratios have been evaluated. The presence of high-mass spin-0 and spin-2 structures is discussed.     

Synthesis and performance of cathode material LiCo0.05Mn1.95O4 − y F y and modify by surface coating with LiCoO2

To investigate the electrochemical properties of LiCo_0.05Mn_1.95O_4???y F _y (y?=?0.025, 0.05, 0.075, 0.1, 0.15) as a cathode material for 4-V class lithium secondary batteries, spinel phases synthesized by sol–gel were examined. X-ray diffraction data reveals that all the materials synthesized are pure spinel structures. The charge–discharge curves demonstrate that LiCo_0.05Mn_1.95O_3.9F_0.1 has the best electrochemical property. LiCo_0.05Mn_1.95O_3.9F_0.1 possesses the initial and stable discharge capacity of 118.3 and 113 mAh/g after 10 cycles at 0.1 C, respectively, while LiCo_0.05Mn_1.95O_3.9F_0.1 possesses the initial and stable discharge capacity of 105.8 and 90.9 mAh/g after 40 cycles at 1 C, respectively. Both the cyclic voltammetry and electrochemical impedance explain the best electrochemical property of LiCo_0.05Mn_1.95O_3.9F_0.1 to some degree. LiCoO₂-coated LiCo_0.05Mn_1.95O_4???y F _y (7 mol%) presents an excellent reversibility than pristine one which possesses the initial and stable discharge capacity of 106.1 and 101.3 mAh/g after 40 cycles at 1 C, respectively.     

Structural Characterization of RF‐Sputtered a‐C:N Thin Films by Raman,IR, and X‐ray Reflectometry Spectroscopies

Abstract

Amorphous carbon nitride thin films (a‐C:N) were deposited from a carbon target, at room temperature onto silicon substrates, by reactive RF sputtering in a gas mixture of argon and nitrogen. The structural properties of these films have been studied by Raman, infrared (IR), and X‐ray reflectometry spectroscopies. Both the IR and Raman spectra of the a‐C:N films reveal the presence of C–C, C?C, C?N, and C≡N bonding types. The Raman spectra analysis shows, an increase of the C≡N triple bonds content when the concentration of nitrogen C(N₂) in the gas mixture is increased. The Raman intensities ratio between the disorder (D) and graphitic (G) bands increases with C(N₂) suggesting an increased disorder with the incorporation of nitrogen in the carbon matrix. The effect of C(N₂) on the density of a‐C:N films was also investigated by X‐ray reflectometry measurement. The increase of the nitrogen concentration C(N₂) was found to have a significant effect on the density of the films: as C(N₂) increases from 0 to 100%, the density of the a‐C:N films decreases slightly from 1.81 to 1.62 g/cm³. The low values of density of the a‐C:N films were related (i) to the absence of C–N single bonds, (ii) to the increase of disorder introduced by the incorporation of nitrogen in the carbon matrix, and (iii) to the presence of the bands around 2350 cm^?1 and 3400 cm^?1 associated with the C–O bond stretching modes and the O–H vibration, respectively, suggesting a high atmospheric contamination by oxygen and water. The presence of these bands suggests the porous character of the studied samples.     

Synthesis and electrochemical performance of Li1+xV3O8 as cathode material prepared by citric acid and tartaric acid assisted sol–gel processes

Lithium-ion battery cathode material Li_1+xV₃O₈ is synthesized by a citric acid/tartaric acid assisted sol–gel method and sintered at 350 °C, 450 °C and 550 °C for 3 h for the formation of Li_1+xV₃O₈ phase. The synthesized samples were fully characterized by FTIR, TG/DTA, XRD, SEM, EIS and charge–discharge tests. Li_1+xV₃O₈ material synthesized by tartaric acid assisted route and sintered at 450 °C for 3 h shows best electro-chemical performance. It shows a high initial capacity of 249 mAh g^?1 and still reserves a discharge capacity of 260 mAh g^?1 after 50 cycles. Moreover, in the case of tartaric assisted products, no capacity decadence is observed in 50 cycles. XRD together with TG/DTA measurements reveal that compared with citric acid assisted products, the adoption of tartaric acid as chelating agent effectively lowers the crystallization temperature of amorphous Li_1+xV₃O₈. Therefore, precursors obtained by tartaric acid route calcinated at 450 °C for 3 h exhibit lower crystallinity and smaller grain size, which contributes to the better electrochemical performance of the cathode electrodes. From EIS measurements, the bulk resistance is reduced, which favors the intercalation and de-intercalation of lithium ions while cycling.     

Improved performance of P3HT：PCBM solar cells by both anode modification and short-wavelength energy utilization using Tb（aca）3phen

The performance of P3HT:PCBM solar cells was improved by anode modification using spin-coated Tb(aca)3phen ultrathin films. The modification of the Tb(aca)3phen ultrathin film between the indium tin oxide(ITO) anode and the PEDOT:PSS layer resulted in a maximum power conversion efficiency(PCE) of 2.99% compared to 2.66% for the reference device, which was due to the increase in the short-circuit current density(Jsc). The PCE improvement could be attributed to the short-wavelength energy utilization and the optimized morphology of the active layers. Tb(aca)3phen with its strong down-conversion luminescence properties is suitable for the P3HT:PCBM blend active layer, and the absorption region of the ternary blend films is extended into the near ultraviolet region. Furthermore, the crystallization and the surface morphology of P3HT:PCBM films were improved with the Tb(aca)3phen ultrathin film. The ultraviolent–visible absorption spectra,atomic force microscope(AFM), and X-ray diffraction(XRD) of the films were investigated. Both anode modification and short-wavelength energy utilization using Tb(aca)3phen in P3HT:PCBM solar cells led to about a 12% PCE increase.