Waveguiding and photoluminescence in Er³⁺-doped Ta₂O₅ planar waveguides

The optimization of erbium-doped Ta2O5 thin film waveguides deposited by magnetron sputtering onto thermally oxidized silicon wafer is described. Optical constants of the film were determined by ellipsometry. For the slab waveguides, background losses below 0.4dB/cm at 633nm have been obtained before post-annealing. The samples, when pumped at 980nm yielded abroad photoluminescence spectrum (FWHM ~50 nm) centred at 1534nm, corresponding to 4 I 13/2 to the 4 I 15/2 transition of Er3+ ion. The samples were annealed up to 600 °C and both photoluminescence power and fluorescence lifetime increase with post-annealing temperature and a fluorescence lifetime of 2.4ms was achieved, yielding promising results for compact waveguide amplifier

A systematic validation of hot Neptunes in TESS data

We statistically validated a sample of hot Neptune candidates applying a two-step vetting technique using DAVE and TRICERATOPS. We performed a systematic validation of 250 transit-like events in the Transiting Exoplanet Survey Satellite (TESS) archive in the parameter region defined by $P\leq 4$ d and $3R_\oplus\leq R\leq 5R_\oplus$. Through our analysis, we identified 18 hot Neptune-sized candidates, with a false positive probability $<50\%$. Nine of these planet candidates still need to be confirmed. For each of the nine targets we retrieved the stellar parameters using ARIADNE and derived constraints on the planetary parameters by fitting the lightcurves with the juliet package. Within this sample of nine candidates, we statistically validated (i.e, with false positive probability < $0.3\%$) two systems (TOI-277 b and TOI-1288 b) by re-processing the candidates with TRICERATOPS along with follow-up observations. These new validated exoplanets expand the known hot Neptunes population and are high-priority targets for future radial velocities follow-up.Comment: 24 pages, 20 figures. Accepted for publication on MNRA

Effect of Growth Temperature on Bamboo-shaped Carbon–Nitrogen (C–N) Nanotubes Synthesized Using Ferrocene Acetonitrile Precursor

This investigation deals with the effect of growth temperature on the microstructure, nitrogen content, and crystallinity of C–N nanotubes. The X-ray photoelectron spectroscopic (XPS) study reveals that the atomic percentage of nitrogen content in nanotubes decreases with an increase in growth temperature. Transmission electron microscopic investigations indicate that the bamboo compartment distance increases with an increase in growth temperature. The diameter of the nanotubes also increases with increasing growth temperature. Raman modes sharpen while the normalized intensity of the defect mode decreases almost linearly with increasing growth temperature. These changes are attributed to the reduction of defect concentration due to an increase in crystal planar domain sizes in graphite sheets with increasing temperature. Both XPS and Raman spectral observations indicate that the C–N nanotubes grown at lower temperatures possess higher degree of disorder and higher N incorporation

Supersymmetric quantum mechanics and supersymmetry breaking

422-426Supersymmetric algebra has been constructed in terms of spinorial charges in complex C3 -space consisting of symmetrical spatial an temporal components and the supersymmetric quantum mechanics has been formulated by identifying the additional temporal components of this space as supertime anticommuting variables. Superfields, superpotentials and covariant derivatives have been derived in terms of anticommuting operators constructed by using additional temporal components of C3 -space and it has been shown that the supersymmetry is weakly broken in these extra temporal dimensions

A simple method for methylmercury, inorganic mercury and ethylmercury determination in plasma samples by high performance liquid chromatography–cold-vapor-inductively coupled plasma mass spectrometry

A simple and sensitive method with a fast sample preparation procedure is proposed for the determination of mercury species in plasma/serum. The method combines online high-performance liquid chromatography separation, Hg cold-vapor formation and inductively coupled plasma mass spectrometry detection. Prior to analysis, plasma (250μL) was accurately pipetted into 15mL conical tubes. Then, an extractant solution containing mercaptoethanol, L-cysteine and HCl was added to the samples following sonication for 10min. Quantitative mercury extraction was achieved with the proposed procedure. Separation of mercury species was accomplished in less than 8min on a C8 reverse phase column with a mobile phase containing 3% v/v methanol+97% v/v (0.5% v/v 2-mercaptoethanol+0.05% v/v formic acid). The method detection limits were found to be 12ngL-1, 5ngL-1 and 4ngL-1 for inorganic mercury, ethylmercury and methylmercury, respectively. Method accuracy is traceable to Standard Reference Material (SRM) 966 Toxic Metals in Bovine Blood from NIST. Additional validation was provided by the analysis of a secondary reference serum sample from the INSQ-Canada. Finally, the method was successfully applied for the speciation of mercury in plasma samples collected from volunteers exposed to methylmercury through fish consumption. For the first time to our knowledge, levels of different species of Hg in plasma samples from riverside populations exposed to MeHg were determined. © 2012 Elsevier B.V

Micro-Raman and dielectric phase transition studies in antiferroelectric PbZrO<SUB>3</SUB> thin films

Antiferroelectric materials are found to be good alternative material compositions for high-charge-storage devices and transducer applications. Lead zirconate (PZ) is a room-temperature antiferroelectric material. The antiferroelectric nature of PZ thin films was studied over a temperature range of 24-300° C, in terms of Raman scattering, dielectric constant, and polarization. Temperature-dependent dielectric and polarization studies indicated a nonabrupt phase transition. To alleviate the extrinsic effects influencing the phase transition behavior, Raman scattering studies were done on laser-ablated PZ thin films as a function of temperature and clear phase transformations were observed

Moduli space for dyons

223-228Analysing the non-Abelian gauge theory of dyon the expression for dyonic mass has been derived and connection of moduli space of monopoles with normalised bosonic and fermionic spaces is established. Supersymmetrising this theory of dyons it has been demonstrated that the modification in supersymmetric algebra due to central charges leads to partial breaking or supersymmetrics with the unbroken supersymmetry pairing the bosonic and fermionic zero modes. The moduli space has been constructed in non-Abelian gauge theory of dyons and its kinematics have been investigated

Dielectric and ferroelectric response of sol-gel derived Pb<SUB>0.85</SUB>La<SUB>0.15</SUB>TiO<SUB>3</SUB> ferroelectric thin films on different bottom electrodes

Sol-gel derived Pb0.85La0.15TiO3 thin films were deposited on Pt, Pt/Si, RuO2/Pt/Si and RuO2/Si bottom electrodes. The structural and microstructural characteristics of the films were studied using X-ray diffraction and atomic force microscopy techniques. Dielectric, ferroelectric and leakage current characteristics were evaluated and depth profile Auger electron spectroscopy was used to obtain direct evidence for reactivity and compositional changes at the film/electrode interface and determine their effect on the ferroelectric and dielectric properties of films. Films deposited on Pt electrode showed a relatively higher dielectric constant of approximately 1300, while the films on RuO2 exhibited lower dielectric constant of only 470. J-t characteristics with leakage current of approximately 10-8 A/cm2 under low biasing field (10 kV/cm) was observed for the films under study. The steady state field dependent dc conductivity was examined by the measurement of J-E characteristics. At very low fields (&lt;30 kV/cm) films followed ohmic behavior and was fitted with a space-charge-limited conduction mechanism in the intermediate fields (30-60 kV/cm). The on-set voltage for the non-linearity was considered as VTFL using which, the trap concentration estimated for films on RuO2/Si electrode was 1.23&#215; 1017 cm-3. Observed current characteristics have been correlated with large interfacial resistance at the film-electrode boundary. In the case of RuO2 bottom electrodes, the dielectric and ferroelectric properties are correlated with the electrode characteristics and Si diffusion at the film-electrode interface

Structural and electrical characteristics of Pb<SUB>0.90</SUB>La<SUB>0.15</SUB>TiO<SUB>3</SUB> thin films on different bottom electrodes

Pb0.90La0.15TiO3 (PLT15) thin films were deposited by the sol-gel method on Pt, Pt/Si, and RuO2 on Si and Pt/Si bottom electrodes. X-ray diffraction, micro-Raman spectroscopy, and atomic force microscopy techniques were used for structural characterization of these films. PLT15 films on different electrodes showed good surface morphology with dense and uniform microstructure. PLT15 films on solution derived RuO2 bottom electrodes show (100) preferred orientation of growth and result in larger crystallites. Films deposited on a Pt bottom electrode show sharp and intense Raman features indicating better crystallinity and insignificant film-electrode interactions. PLT15 film on a Pt bottom electrode exhibited higher dielectric constant (1300 at 100 kHz) and high values of Pm and Pr, 68 and 46 &#181; C/cm2, respectively, compared to other electrodes. Films on a RuO2 bottom electrode showed relatively inferior dielectric and ferroelectric properties. The ac field dependence of dielectric permittivity at subswitching fields was fitted using the Rayleigh law. It was found that ~22% of the total measured permittivity was due to irreversible domain wall displacement for the films on a Pt electrode. The reversible polarization components estimated from the capacitance-voltage (C-V) and quasistatic hysteresis measurements showed that Prev/Psat at Vmax for the case of Pt/Si (24%), was larger than that of Pt (11%) bottom electrodes. The observed results were correlated with the domain wall pinning at the disturbed film-electrode interface