Search results for "Toe"
showing 10 items of 3824 documents
Synthesis and characterization of GaN/ReS2, ZnS/ReS2 and ZnO/ReS2 core/shell nanowire heterostructures
2020
This research was funded by the ERDF project “Smart Metal Oxide Nanocoatings and HIPIMS Technology”, project number: 1.1.1.1/18/A/073. Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART².
Visible to vacuum-UV range optical absorption of oxygen dangling bonds in amorphous SiO2
2011
Synthetic silica glass with an optical absorption spectrum dominated by oxygen dangling bonds (nonbridging oxygen hole centers, or NBOHCs) and having negligible (1%) contribution from the usually copresent Si dangling bonds (E\ensuremath{'}-centers), was prepared by room temperature ultraviolet photobleaching of high SiOH content (``wet'') silica, irradiated by F${}_{2}$ laser (7.9 eV) at $T$ = 80 K. This allowed us to obtain the up-to-now controversial optical absorption spectrum of NBOHC in the ultraviolet and vacuum-ultraviolet (UV-VUV) region of the spectrum and to show that it is semicontinuous from 4 to 7.8 eV and cannot be represented by a pair of distinct Gaussian bands. Since NBOHC…
Optical determination of the oxygen content of YBa2Cu3O6+x thin films by IR reflectance and transmittance measurements
2001
Abstract Recent studies of the optical properties of YBa2Cu3O6+x (YBCO) single crystals by several authors have shown that the optical conductivity in the infrared spectral region is a sensitive function of the oxygen content of the samples. Infrared spectroscopy thus offers a possibility for oxygen concentration analysis and is an alternative to other methods such as (i) the X-ray determination of the length of the c-axis and (ii) spectroscopic ellipsometry at an electronic transition band centered around 4.1 eV whose strength decreases with increasing oxygen content. We explore the applicability of the IR optical method for the case of YBCO thin films of about 300 nm thickness which are e…
Anti-recombination organic dyes containing dendritic triphenylamine moieties for high open-circuit voltage of DSSCs
2013
Abstract Three novel sensitizers with dendritic triphenylamine moieties were synthesized and used for dye-sensitized solar cells (DSSCs). Their absorption spectra, electrochemical and photovoltaic properties were extensively investigated. All three DSSCs exhibit high open-circuit voltage over 0.8 V. The photovoltaic results indicate that the dendritic triphenylamine units improve the open-circuit voltage, which is attributed to the retardation of charge recombination, demonstrating that non-planar and larger molecules exert better blocking function. Under standard global AM 1.5 solar conditions, the best performance of the DSSCs exhibits a short-circuit current density of 10.35 mA cm−2, an …
Filament-induced visible-to-mid-IR supercontinuum in a ZnSe crystal: Towards multi-octave supercontinuum absorption spectroscopy
2016
Abstract We report on the generation of multiple-octave supercontinuum laser source spanning from 0.5 μm to 11 μm induced by multi-filamentation in a ZnSe crystal. The generated supercontinuum is both spatially and spectrally characterized. It is then exploited in a proof-of-principle experiment for methane spectroscopy measurements by means of the supercontinuum absorption spectroscopy technique. The entire absorption spectrum is successfully recorded within the whole spectral bandwidth of the supercontinuum. Experimental results are in fairly good agreement with the HITRAN database, confirming the reliability and stability over several hours of the generated supercontinuum.
Dual-Comb Spectroscopy With Frequency-Agile Lasers
2015
Multiheterodyne frequency comb spectroscopy without mode-locked lasers is reported in the near-infrared C and L telecommunication bands. The system without active stabilization combines high signal-to-noise ratio, rapid tuning and moderate multiplex spectral span.
Transient absorption with a femtosecond tunable excitation pump reveals the emission kinetics of color centers in amorphous silica.
2021
We report a set of femtosecond (fs) transient absorption (TA) measurements following the dynamics of the so-called nonbridging oxygen hole center in silica, a model color center in wide bandgap amorphous solids, characterized by a very large Stokes shift between the UV excitation and its associated red emission at 1.9 eV. The changes in the TA spectrum were probed in the UV-visible range at various delays after photoexcitation and analyzed as a function of the UV excitation energy, in single-photon absorption conditions. The combination of the experiments helps to clarify the defect photocycle, highlighting how TA measurements with tunable UV excitation could represent a powerful tool to in…
Terahertz spectroscopy for all-optical spintronic characterization of the spin-Hall-effect metals Pt, W and Cu80Ir20
2018
Identifying materials with an efficient spin-to-charge conversion is crucial for future spintronic applications. In this respect, the spin Hall effect is a central mechanism as it allows for the interconversion of spin and charge currents. Spintronic material research aims at maximizing its efficiency, quantified by the spin Hall angle and the spin-current relaxation length . We develop an all-optical contact-free method with large sample throughput that allows us to extract and . Employing terahertz spectroscopy and an analytical model, magnetic metallic heterostructures involving Pt, W and Cu80Ir20 are characterized in terms of their optical and spintronic properties. The validity of our …
Laser irradiation of carbon–tungsten materials
2014
Carbon–tungsten layers deposited on graphite by thermionic vacuum arc (TVA) were directly irradiated with a femtosecond terawatt laser. The morphological and structural changes produced in the irradiated area by different numbers of pulses were systematically explored, both along the spots and in their depths. Although micro-Raman and Synchrotron-x-ray diffraction investigations have shown no carbide formation, they have shown the unexpected presence of embedded nano-diamonds in the areas irradiated with high fluencies. Scanning electron microscopy images show a cumulative effect of the laser pulses on the morphology through the ablation process. The micro-Raman spatial mapping signalled an…
Low-frequency band gap in cross-like holey phononic crystal strip
2018
International audience; A silicon-based cross-like holey phononic crystal (PnC) strip is proposed for the control of elastic waves in the field of micro-electro-mechanical systems (MEMS). The goal is to obtain a broad bandgap at low frequencies with a lightweight structure. In this respect, the effects of varying the in-plane and the out-of-plane geometry parameters are discussed. After design, a gap-to-midgap ratio of 47% is obtained with an intermediate filling fraction of the solid material and a small thickness of the strip. The band gap can be moved to an extremely low frequency range while keeping the strip significantly smaller than previously reported PnC strips. The transmission pr…