Search results for "CONDENSED MATTER"
showing 10 items of 13918 documents
Copper Induces a Core Plasmon in Intermetallic Au(144,145)–xCux(SR)60 Nanoclusters
2015
The electronic structure and optical absorption spectra of intermetallic thiol-stabilized gold-copper clusters, having 144-145 metal atoms and 60 thiols, were studied by ab initio computations. The widely known icosahedral-based cluster model from the work of Lopez-Acevedo et al. (2009) was used, and clusters doped with one to 30 copper atoms were considered. When doped inside the metal core, copper induces dramatic changes in the optical spectrum as compared to the previously studied all-gold Au144(SR)60. An intense broad absorption peak develops in the range 535-587 nm depending on the amount of doping and doping sites. This result agrees very well with recent experiments by the Dass grou…
Optical Absorption of Excimer Laser‐Induced Dichlorine Monoxide in Silica Glass and Excitation of Singlet Oxygen Luminescence by Energy Transfer from…
2021
An optical absorption (OA) band of interstitial dichlorine monoxide molecules with peak at 4.7 eV and halfwidth 0.94 eV is identified in F2 laser - irradiated (photon energy=7.9 eV) synthetic silica glass bearing both interstitial O2 and Cl2 molecules. Alongside with intrinsic defects, this OA band can contribute to solarization of silica glasses produced from SiCl4. While the formation of ClClO is confirmed by its Raman signature, its structural isomer ClOCl may also contribute to this induced OA band. Thermal destruction of this band between 300C and 400C almost completely restores the pre-irradiation concentration of interstitial Cl2. An additional weak OA band at 3.5 eV is tentatively a…
Radioluminescence Response of Ce-, Cu-, and Gd-Doped Silica Glasses for Dosimetry of Pulsed Electron Beams
2021
Radiation-induced emission of doped sol-gel silica glass samples was investigated under a pulsed 20-MeV electron beam. The studied samples were drawn rods doped with cerium, copper, or gadolinium ions, which were connected to multimode pure-silica core fibers to transport the induced luminescence from the irradiation area to a signal readout system. The luminescence pulses in the samples induced by the electron bunches were studied as a function of deposited dose per electron bunch. All the investigated samples were found to have a linear response in terms of luminescence as a function of electron bunch sizes between 10−5 Gy/bunch and 1.5×10−2 Gy/bunch. The presented results show that these…
Near‐IR Radiation‐Induced Attenuation of Aluminosilicate Optical Fibers
2021
The X-ray radiation-induced attenuation (RIA) growth kinetics are studied online in different single-mode aluminosilicate optical fibers in the near-IR (NIR) domain to evaluate their potential in terms of dosimetry. The optical fibers differ by Al contents, core sizes, drawing parameters, and also by a preform deposition process. The data show no dependence of the RIA on all these parameters, a positive result for the design of point or distributed radiation detectors exploiting RIA to monitor the dose. The RIA growth rate is unchanged for dose rates changing from 0.073 to 6.25 Gy(SiO2) s−1, and the RIA linearly increases with the dose up to 2 kGy(SiO2). Small but noticeable RIA changes are…
Ge quantum well plasmon-enhanced quantum confined Stark effect modulator
2014
ABSTRACTWe theoretically and experimentally investigate a novel modulation concept on silicon (Si) based on the combination of quantum confinement and plasmon enhancement effects. We experimentally study the suitability of Ge/SiGe quantum wells (QWs) on Si as the active material for a plasmon-enhanced optical modulator. We demonstrate that in QW structures absorption and modulation of light with transverse magnetic (TM) polarization are greatly enhanced due to favorable selection rules. Later, we theoretically study the plasmon propagation at the metal-Ge/SiGe QW interface. We design a novel Ge/SiGe QW structure that allows maximized overlap between the plasmonic mode and the underlying Ge/…
Evolution of microstructure and related optical properties of ZnO grown by atomic layer deposition.
2013
A study of transmittance and photoluminescence spectra on the growth of oxygen-rich ultra-thin ZnO films prepared by atomic layer deposition is reported. The structural transition from an amorphous to a polycrystalline state is observed upon increasing the thickness. The unusual behavior of the energy gap with thickness reflected by optical properties is attributed to the improvement of the crystalline structure resulting from a decreasing concentration of point defects at the growth of grains. The spectra of UV and visible photoluminescence emissions correspond to transitions near the band-edge and defect-related transitions. Additional emissions were observed from band-tail states near th…
Optical and structural properties of Al 2 O 3 /ZnO nanolaminates deposited by ALD method
2014
International audience; We report on the investigation of optical and structural properties of Al2O3/ZnO nanolaminates. The nanolaminates were deposited on Si and glass substrates by Atomic layer deposition method. Structural properties of nanolaminates were studied by SEM, GIXRD, and AFM. Optical characterization was performed by transmittance and photoluminescence spectroscopy. Complex analysis of monolayer properties was done by ellipsometry. Optical constants for Al2O3 and ZnO monolayer were calculated.
Atomic layer deposition of AlN from AlCl3 using NH3 and Ar/NH3 plasma
2018
The atomic layer deposition (ALD) of AlN from AlCl3 was investigated using a thermal process with NH3 and a plasma-enhanced (PE)ALD process with Ar/NH3 plasma. The growth was limited in the thermal process by the low reactivity of NH3, and impractically long pulses were required to reach saturation. Despite the plasma activation, the growth per cycle in the PEALD process was lower than that in the thermal process (0.4A ° vs 0.7A ° ). However, the plasma process resulted in a lower concentration of impurities in the films compared to the thermal process. Both the thermal and plasma processes yielded crystalline films; however, the degree of crystallinity was higher in the plasma process. The…
Long-transient conoscopic pattern technique
1999
0038-1098; Recent results on laser induced anisotropy in terbium gallium garnet are extended to the dynamic regime. We observed that the characteristic conoscopic pattern formation time presents a quadratic dependence on the beam size. The observed pattern intensity is accounted for by a simple analytical formula. The transient refractive index change due to thermal stress in the terbium gallium garnet is determined. (C) 1999 Elsevier Science Ltd. All rights reserved.
Unravelling the Intertwined Atomic and Bulk Nature of Localised Excitons by Attosecond Spectroscopy
2021
The electro-optical properties of most semiconductors and insulators of technological interest are dominated by the presence of electron-hole quasi-particles, called excitons. The manipulation of excitons in dielectrics has recently received great attention, with possible applications in different fields including optoelectronics and photonics. Here, we apply attosecond transient reflection spectroscopy in a sequential two-foci geometry and observe sub-femtosecond dynamics of a core-level exciton in bulk MgF2 single crystals. Furthermore, we access absolute phase delays, which allow for an unambiguous comparison with theoretical calculations. Our results show that excitons surprisingly exhi…