Search results for "Wide-band"
showing 10 items of 60 documents
Luminescence Properties of ZnO Nanocrystals and Ceramics
2008
The luminescence excitation spectra, luminescence spectra and the nanosecond-scale decay kinetics were studied. The ZnO and ZnO:Al nanopowders were prepared by vaporization-condensation in a solar furnace using different raw powders: commercial, hydrothermal and those obtained by plasma synthesis. Exciton-phonon as well as exciton-exciton interaction processes in nanopowders, a bulk crystal and ZnO ceramics were studied and compared. The fast decay and low afterglow intensity of ZnO nanopowders and ceramics support these materials for scintillators.
BVI photometry in NGC 6611
2007
VizieR online Data Catalogue associated with article published in journal Astronomy & Astrophysics with title 'Correlation between the spatial distribution of circumstellar disks and massive stars in the open cluster NGC 6611. Compiled catalog and cluster parameters.' (bibcode: 2007A&A...462..245G)
BVI & JHK photometry of NGC 3960
2004
VizieR online Data Catalogue associated with article published in journal Astronomy & Astrophysics with title 'Parameter properties and stellar population of the old open cluster NGC 3960.' (bibcode: 2004A&A...417..945P)
Density-functional study of pressure-induced phase transitions and electronic properties of Zn2V2O7
2021
We report a study of the high-pressure behavior of the structural and electronic properties of Zn2V2O7 by means of first-principle calculations using the CRYSTAL code. Three different approaches have been used, finding that the Becke–Lee–Yang–Parr functional is the one that best describes Zn2V2O7. The reported calculations contribute to the understanding of previous published experiments. They support the existence of three phase transitions for pressures smaller than 6 GPa. The crystal structure of the different high-pressure phases is reported. We have also made a systematic study of the electronic band-structure, determining the band-gap and its pressure dependence for the different poly…
Correlation between Zn vacancies and photoluminescence emission in ZnO films.
2006
Photoluminescence and positron annihilation spectroscopy have been used to characterize and identify vacancy-type defects produced in ZnO films grown on sapphire by metal-organic chemical-vapor deposition. The photoluminescence of the samples in the near band edge region has been studied, paying particular attention to the emission at 370.5 nm (3.346 eV). This emission has been correlated to the concentration of Zn vacancies in the films, which has been determined by positron annihilation spectroscopy. Jesus.Zuniga@uv.es Vicente.Munoz@uv.es
Modulation of the electronic properties of GaN films by surface acoustic waves
2003
We report on the interaction between photogenerated electron-hole pairs and surface acoustic waves (SAW) in GaN films grown on sapphire substrates. The spatial separation of photogenerated carriers by the piezoelectric field of the SAW is evidenced by the quenching of the photoluminescence (PL) intensity. The quenching levels in GaN are significantly smaller than those measured in GaAs under similar conditions. The latter is attributed to the lower exciton ionization efficiency and carrier separation probabilities mediated by the piezoelectric effect. The PL spectra also evidence energy shifts and broadenings of the electronic transitions, which are attributed to the band gap modulation by …
The TESS Grand Unified Hot Jupiter Survey I. 10 planets
2022
Hot Jupiters-short-period giant planets-were the first extrasolar planets to be discovered, but many questions about their origin remain. NASA's Transiting Exoplanet Survey Satellite (TESS), an all-sky search for transiting planets, presents an opportunity to address these questions by constructing a uniform sample of hot Jupiters for demographic study through new detections and unifying the work of previous ground-based transit surveys. As the first results of an effort to build this large sample of planets, we report here the discovery of 10 new hot Jupiters (TOI-2193Ab, TOI-2207b, TOI-2236b, TOI-2421b, TOI-2567b, TOI-2570b, TOI-3331b, TOI-3540Ab, TOI-3693b, TOI-4137b). All of the planets…
Improving the Performance of Quasi-Hemispherical CdZnTe Detectors Using Infrared Stimulation
2012
The influence of monochromatic optical stimulation with wavelengths from 400 to 1100 nm on the characteristics of CdZnTe quasi-hemispherical detectors was studied. It was found that illumination with infrared (IR) light with wavelengths of 870-900 nm close to the absorption edge of the CdZnTe significantly improves the performance of the detector at room temperature. Improvement can be achieved with low-intensity IR illumination at 1-300 μW depending on the chosen wavelength of illumination. Higher intensity illumination was observed to lead to the degradation of the detector's spectrometric characteristics. IR radiation was noted to influence the detector's sensitivity, changing the equili…
Nanochemistry Aspects of Titania in Dye Sensitized Solar Cells
2009
We analyze the main nanochemistry factors affecting photovoltaic performance in TiO2 employed as wide bandgap semiconductor in dye-sensitized solar cells (DSCs). What is the best morphology of the oxide? Which processes yield the required structures? Finally, putting the discussion in the context of the rapid evolution of photovoltaic technologies, we argue that new titania nanostructures will form the basic component of second-generation solar modules based on dye solar cells.
Low-cost high-haze films based on ZnO nanorods for light scattering in thin c-Si solar cells
2015
Light scattering from ZnO nanorods (NR) is investigated, modeled, and applied to a solar cell. ZnO NR (120-1300 nm long, 280-60 nm large), grown by low-cost chemical bath deposition at 90 degrees C, exhibit diffused-to-total transmitted light as high as 70% and 30% in the 400 and 1000 nm wavelength range, respectively. Data and scattering simulation show that ZnO NR length plays a crucial role in light diffusion effect. A transparent ZnO NR film grown on glass and placed on top of a 1 mu m thick c-Si solar cell is shown to enhance the light-current conversion efficiency for wavelengths longer than 600 nm. (C) 2015 AIP Publishing LLC.