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The properties of the acoustic modes are sensitive to magnetic activity. The unprecedented long-term Kepler photometry, thus, allows stellar magnetic cycles to be studied through asteroseismology. We search for signatures of magnetic cycles in the seismic data of Kepler solar-type stars. We find evidence for periodic variations in the acoustic properties of about half of the 87 analysed stars. In these proceedings, we highlight the results obtained for two such stars, namely KIC 8006161 and KIC 5184732.
This study aims to assess current practices of Canadian physicians providing botulinum toxin-A (BoNT-A) treatments for children with hypertonia and to contrast these with international “best practice” recommendations, in order to identify practice variability and opportunities for knowledge translation.
Thirteen Canadian physicians assembled to develop and analyze results of a cross-sectional electronic survey, sent to 50 physicians across Canada.
Seventy-eight percent (39/50) of physicians completed the survey. The most frequently identified assessment tools were Gross Motor Function Classification System, Modified Tardieu Scale and neurological examination. Goal-setting tools were infrequently utilized. Common indications for BoNT-A injections and the muscles injected were identified. Significant variability was identified in using BoNT-A for hip displacement associated with hypertonia. The most frequent adverse event reported was localized weakness; 54% reporting this “occasionally“ and 15% “frequently”. Generalized weakness, fatigue, ptosis, diplopia, dysphagia, aspiration, respiratory distress, dysphonia and urinary incontinence were reported rarely or never. For dosage, 52% identified 16 Units/kg body weight of Botox® as maximum. A majority (64%) reported a maximum 400 Units for injection at one time. For localization, electrical stimulation and ultrasound were used infrequently (38% and 19% respectively). Distraction was the most frequently used pain-management technique (64%).
Canadian physicians generally adhere to international best practices when using BoNT-A to treat paediatric hypertonia. Two knowledge-translation opportunities were identified: use of individualized goal setting prior to BoNT-A and enhancing localization techniques. Physicians reported a good safety profile of BoNT-A in children.
Advancement of ion acceleration by intense laser pulses is studied with ultra-thin nanometer-thick diamond like carbon and micrometer-thick Titanium target foils. Both investigations aim at optimizing the electron density distribution which is the key for efficient laser driven ion acceleration. While recently found maximum ion energies achieved with ultra-thin foils mark record values micrometer thick foils are flexible in terms of atomic constituents. Electron recirculation is one prerequisite for the validity of a very simple model that can approximate the dependence of ion energies of nanometer-thick targets when all electrons of the irradiated target area interact coherently with the laser pulse and Coherent Acceleration of Ions by Laser pulses (CAIL) becomes dominant. Complementary experiments, an analytical model and particle in cell computer simulations show, that with regard to ultra-short laser pulses (duration ~45 fs at intensities up to 5 × 1019 W/cm2) and a micrometer-thick target foil with higher atomic number a close to linear increase of ion energies manifests in a certain range of laser intensities.
In this paper we report on an experimental study of high harmonic radiation generated in nanometer-scale foil targets irradiated under normal incidence. The experiments constitute the first unambiguous observation of odd-numbered relativistic harmonics generated by the v × B component of the Lorentz force verifying a long predicted property of solid target harmonics. Simultaneously the observed harmonic spectra allow in-situ extraction of the target density in an experimental scenario which is of utmost interest for applications such as ion acceleration by the radiation pressure of an ultraintense laser.
A new technique for improving the diffusion barrier properties of thin, thermallyevaporated nickel, chromium and nichrome films on silicon is described. In this technique, known as “Rapid Thermal Annealing” (RTA), profound differences in the diffusion barrier properties of the films annealed in ammonia ambient at 550-750°C, in comparison to films annealed only in vacuum, were observed. The films annealed in ammonia retained their integrity while the films annealed in vacuum showed diffusion of the silicon into the metal overlayer throughout the entire thickness of the metal in some cases. The film sheet resistance increase for the latter was consistent with the formation of the metal silicide. The possibility of extending this technique to electroplated films used in integrated and hybrid device fabrication is being studied.
Ion implanted CoSi2 as a gate doping source has been studied as a compatible process to the Silicide-As Diffusion-Source (SADS) process which has been widely considered for shallow source/drain junction formation. The effects of the polysilicon gate microstructure on diffusion behavior and the thermal stability of CoSi2 has been investigated. It has been found that CoSi2 formed on reoxidized polysilicon gates has poor thermal stability but requires short time to achieve degenerate doping near the polysilicon/gate oxide interface. On the other hand, CoSi2 formed on as-deposited amorphous silicon has excellent thermal stability but requires longer time to achieve degenerate doping near the polysilicon/gate oxide interface. The trade-off between the required thermal budget to achieve degenerate doping and thermal stability of the CoSi2/polysilicon gate structure will be discussed. In optimizing the process, our results indicated that reoxidized amorphous Si gates have both good thermal stability as well requiring short time to achieve degenerate doping. The thermal degradation of CoSi2 was found to have little effect on the gate oxide breakdown voltage.
A multiprocess CVD system with the following main features is designed and constructed: the wafer holder is made of a Si wafer with diameter larger than the process wafers. This larger holder produces a better temperature uniformity on the process wafer. A good thermal contact between holder and process wafer is obtained by an electrostatic clamp. The holder supports the process wafer facing down. A remote plasma is produced in a small chamber inside the process chamber. The 100 KHz RF frequency keeps the system very simple and cheap while still reasonable ionization is achieved. SiO2 films were deposited using SiH4 and O2 with and without remote plasma of O2. At low temperatures and 1.5 Torr, process activation energies of about 0.9 and 0.3 eV were obtained respectively.
In this paper, a detailed reliability investigation is presented for ultra-thin tunneling (∼50 Å) oxides grown in N2O ambient using rapid thermal processing (RTP). These N2Oss-oxides are compared with oxides of identical thickness grown in O2 ambient by RTP. The reliability investigations include time-dependent dielectric breakdown as well as stress-induced leakage current in MOS capacitors with these gate dielectrics. Results show that ultra-thin N2O-oxides show much improved reliability as compared to oxide grown in O2 ambient.
Proximity rapid thermal diffusion is presented as a doping process for fabrication of very shallow junctions. The kinetics of Si doping with B, P and As is investigated using sheet resistance measurements, secondary ion mass spectroscopy and FTIR analyses. The efficiency of doping is affected by the dopant transport in the SOD which depends on the structure and composition of the SOD.
Process modules for MOS gate fabrication were developed which can be completed subsequently in one RTP reactor: atmospheric process sequences for gate oxides and oxynitrides as well as low pressure chemical vapor deposition of polysilicon (RTCVD). Prior to the Rapid Thermal Oxidation (RTO), the wafers were treated with a Rapid Thermal Cleaning process (RTC) in H2/Ar ambient. After the desoxidation step the RTO was done in O2/H2/Ar followed by an anneal (RTA) for the gate oxide or a nitridation in NH3 (RTN) and reoxidation for the oxynitrides, respectively. The polysilicon gate electrode was fabricated either by RTCVD in situ or in a conventional furnace reactor. The two-step RTCVD process resulted in a very good thickness uniformity for the polysilicon layers of 3% (3mm from the edge). The influence of the process variations on breakdown field, fixed oxide charge, interface state density, flatband voltage, and threshold voltage of the different types of gate dielectrics was investigated. The charges and voltages were determined by LF-HF CV measurements. In order to characterize the radiation tolerance of electronic devices, radiation induced flatband and threshold voltage shifts as well as the build up of interface charges were determined. The irradiation was performed at a Co - 60 gamma source. Breakdown fields in the range of 19 MV/cm, interface state densities of less than 109 eV−2cm−2, and radiation induced threshold voltage shifts below 0.1 V after 1.5 Mrad(Si) were obtained.
In this paper, B diffusion in Si with BF2-implanted CoSi2 as a diffusion source has been studied using SIMS analysis. The concentration-dependent diffusivity of B in single crystal Si is obtained by Boltzmann-Matano analysis. The data show that the B diffusivity in single crystal Si is more than one order of magnitude higher than the published data where a conventional B diffusion source (BN or B2H2) is used. Anomalous concentration dependence of the B diffusivity in Si for ultra-shallow B SIMS profiles was also observed. Possible physical mechanisms which involve implant damage in the Si substrate, the generation of point defects such as Si vacancies and interstitials during silicide formation, and B-defect interactions are discussed.
The effects of heat treatment of polysilicon and amorphous Si films on their microstructure and thermal stability of polycides formed on these films have been studied. The number of grain boundaries decreases after pre-silicidation heat treatment in polysilicon due to grain growth but increases in amorphous Si due to nucleation. Since the thermal stability of CoSi2 polycide films was found to be closely related to the number of grain boundaries in the underlying silicon substrate, pre-silicidation heat treatments degrade the thermal stability of CoSi2 on as-deposited amorphous Si and improve the thermal stability of CoSi2 on asdeposited polysilicon. Doping does not have as pronounced an effects as substrate microstructure on CoSi21 polycide thermal stability, especially when dopants are introduced after silicidation by ion implantation.
Self aligned refractory metal silicides such as titanium disilicide have been used extensively in VLSI and ULSI structures. Unlike earlier work which has relied on undoped substrates and a single implant species, in the present study TiSi2 formation on phosphorous doped poly-Si in the presence of multiple dopants has been investigated. TEM micrographs are discussed which show the difference in silicide formation for the case of the BF2 and arsenic implanted samples. We have found that the presence of fluorine in the BF2 implant retards the silicide formation for phosphorous doped poly-Si substrates. Additionally, the effect of substrate grain size on TiSi2 formation has been investigated using undoped α-Si and poly-Si substrates.
Thermal stability of TiSi2 on blank, high–dose BF2+–, B+–, F+–, As+–, and P+–implanted silicon has been studied by both cross–sectional and plan–view transmission electron microscopy as well as by sheet resistance measurements. The surface morphology of TiSi2 was found to be significantly influenced by the implantation in silicon substrate.
Simultaneous presence of B and F was found to be most effective in stabilizing the TiSi2 thin films. Sheet resistance data were found to correlate well with the morphological and microstructural observation. The mechanisms for the stabilization of silicide films are discussed.
TiN diffusion barriers have been widely used in submicron contact structures, due to its good adhesion (to SiO2, W, Al and Si) properties, low diffusivity (for Si, W and Al) and compatibility with TiSi2 processing. The purpose of this paper is to present the results of physical and electrical characterization of contact structures with a TiN barrier and W plugs. Two different barrier metal processes were compared, Viz: sputtered Ti followed by post RTN and Ti/TiN films followed by post RTA in the range of 600° to 800°C. The devices were thermal stressed at 450°C for 7 hrs after W plug formation and Al metallization. Ti/TiN films with post RTA are generally superior barrier layers than Ti films with post RTA as shown by electrical characterization of contact resistance and barrier integrity. The relationship between electrical properties and microstructure for the two different barrier structures is discussed. W/TiN and TiN/TiSi2 interface structures were characterized using high resolution TEM. TiSi2 was found to be epitaxially grown during RTA, under certain process conditions. The crystal structure of TiSi2 was determined from electron diffraction patterns.
InAs/(GaIn)Sb superlattice photodiodes with a cutoff wavelength of 8.711μm show adynamic impedance of R0A= 1.5 kωcm2at 77 K and a responsivity of 2 A/W, corresponding to a detectivity of D*= 1 x 1012 cmv√Hz/W. Diffusion limited performance is observed above 100 K. At lower temperatures the diodesare limited by generation-recombination currents. An analysis of the influence of different diode sidewall passivations on the surface contribution to the diode leakage current is presented. The out-of-plane electron mobility as well as the relative contributions of the electron and hole diffusion currents to the diode current were determined by a measurement of the magnetic field dependence of the reverse saturation current density of the diodes
The present work reports phase transformations of thin films of C60 irradiated with 100 MeV 197Au8+ ions. This work is in continuation with our earlier work using 58Ni10+ and 16O6+ ions, to study the modification in C60 thin films. The study of C60 thin films using 197Au8+ ions, provides us enough additional data to investigate thoroughly the role of Se in causing phase transformations under different ion fluences. The Raman spectra indicate that swift heavy ion (SHI) irradiation results in several transformations of crystalline C60. At low fluences along with the fragmentation of C60 there is dimer/polymer formation. As fluence increases the dimer/polymer content first rises, optimizes, decreases and finally vanishes at very high fluences. At high fluences, all the C60 molecules as well as the polymer C60 break up, possibly resulting in nano-crystalline graphite embedded in amorphous carbon (a-C).
Information about quantum dot (QD) asymmetry is derived by analyzing the polarization properties of the time-integrated four wave mixing (FWM) signal. The lowering of QD symmetry results in the splitting of bright J= +/-1 exciton states. This causes the polarization oscillation of circularly excited excitons between these two split states. In a QD ensemble with a random distribution in the exciton level splitting, this results in the decay of the difference in FWM signals observed in scattering of σ+ and σ+ polarized light on the population grating created by two σ+ pulses, the decay time reflecting the degree of QD asymmetry. We have investigated the decay time of the difference in two polarized signals for quantum dots of equal size, grown in a glass matrix under different conditions. Increasing growth temperature and decreasing growth time lead to lowering of QD symmetry. We discuss this experimental result in terms of kinetics of nanoparticle growth in glass.
Experiments on ion acceleration by irradiation of ultra-thin diamond-like carbon (DLC) foils, with thicknesses well below the skin depth, irradiated with laser pulses of ultra-high contrast and linear polarization, are presented. A maximum energy of 13 MeV for protons and 71 MeV for carbon ions is observed with a conversion efficiency of ~10%. Two-dimensional particle-in-cell (PIC) simulations reveal that the increase in ion energies can be attributed to a dominantly collective rather than thermal motion of the foil electrons, when the target becomes transparent for the incident laser pulse.