Search results for "Annealing"
showing 10 items of 434 documents
Multicolor upconversion luminescence of GdVO4:Ln3+/Yb3+ (Ln3+ = Ho3+, Er3+, Tm3+, Ho3+/Er3+/Tm3+) nanorods
2016
Lanthanide-doped GdVO4 nanorods that exhibit upconversion emission under 982 nm excitation have been prepared by a facile room-temperature chemical co-precipitation method followed by a subsequent annealing at temperatures of 600 degrees C, 800 degrees C and 1000 degrees C. Multicolor upconversion emission, including white, was achieved by tuning the concentrations of dopant lanthanide ions (Ho3+, Er3+, Tm3+ and Yb3+) in GdVO4. It is found that four GdVO4 samples emit light with the white chromaticity coordinates of (0.326, 0.339), (0.346, 0.343), (0.323, 0327) and (0.342, 0.340) respectively, under a single-wavelength NIR excitation. These coordinates are very close to the standard equal e…
In situobservation of the generation and annealing kinetics of E ′ centres induced in amorphous SiO2by 4.7 eV laser irradiation
2011
The kinetics of E' centers induced in silica by 4.7eV laser irradiation was investigated observing in situ their optical absorption band at 5.8 eV. After exposure the defects decay due to reaction with diffusing molecular hydrogen of radiolytic origin. Hydrogen-related annealing is active also during exposure and competes with the photo-induced generation of the centers until a saturation is reached. The concentrations of E' and H2 at saturation are proportional, so indicating that the UV-induced generation processes of the two species are correlated. These results are consistent with a model in which E' and hydrogen are generated from a common precursor Si-H.
Investigation of Annealing Conditions on Electrochemically Deposited CZTS Film on Flexible Molybdenum Foil
2016
In thiswork, the electrodeposition of Cu2ZnSnS4 thin films on molybdenum thin foilwas reported. In order to guarantee co-deposition of elements with different standard electrochemical potential, an aqueous electrolyte added with ligand agents was used. I addition, deposition parameters were carefully chosen, in order to ensure good quality and suitable composition of the films. The deposited films were sulfurized in controlled atmosphere at 580?C, scrutinizing the influence of the annealing conditions on the features of the films. Structure, morphology and composition were investigated by XRD SEM, EDS and Raman spectroscopy. Results reveal the growth of good quality films, with a uniform mo…
Local structure of ball-milled LaNi5 hydrogen storage material by Ni K-edge EXAFS
2010
Abstract Local structure of the nanostructured LaNi5 hydrogen storage alloys, prepared by ball-milling, has been studied using Ni K-edge extended X-ray absorption fine structure spectroscopy. Results indicate that the ball-milling up to 100 h results in the production of nanoparticles characterized by large atomic disorder and slightly reduced unit-cell volume, compared to the bulk LaNi5. High temperature annealing appears to help in partial recovery of atomic order in the ball-milled samples; however, long-time ball-milled samples retain large disorder even after the high temperature annealing. The results suggest that the large disorder and the reduced unit-cell volume might be causing a …
Characterization of the defect density states in MoOx for c-Si solar cell applications
2021
Thin layers of MoOx have been deposited by thermal evaporation followed by post-deposition annealing. The density of states distributions of the MoOx films were extracted deconvoluting the absorption spectra, measured by a photothermal deflection spectroscopy setup, including the small polaron contribution. Results revealed a sub-band defect distribution centered 1.1 eV below the conduction band; the amplitude of this distribution was found to increase with post-deposition annealing temperature and film thickness.
Phase evolution by thermal treatment of equimolar cobalt–magnesium cordierite glass powders
2004
Abstract The structural evolution with annealing time at temperatures between 900 and 1100 °C of loosely compacted equimolar cobalt–magnesium cordierite glass powder was reported. The glass, with composition MgCoAl4Si5O18, was prepared by melting a glass precursor, previously synthesized by a semiwet method, at 1650 °C. Field emission scanning electron microscopy (FESEM) of isothermally heated glasses at 900 and 950 °C revealed increased phase separation with thermal treatment. X-ray diffraction (XRD) results of these powders indicated that the first crystalline phase formed was μ cobalt-containing cordierite which transformed to α cordierite with longer annealing. At the beginning of the μ…
Growth of glass-embedded Cu nanoparticles: A low-frequency Raman scattering study
2012
International audience; Several populations of Cu spherical nanoparticles grown in a silicate glass at different temperatures with respect to the glass transition temperature were studied using high-resolution, low-frequency Raman scattering and optical absorption. The analysis of the spectra shows that the annealing of the doped glass at temperatures close to T-g leads to the formation of metallic copper nanoparticles with high crystallinity, whereas lower-temperature and higher-temperature annealings result in the formation of poorer nanoparticle assemblies in terms of size distribution and/or nanocrystallinity. It is also shown that in the case where the optical data do not unambiguously…
Modification of the sheet resistance under Ti/Al/Ni/Au Ohmic contacts on AlGaN/GaN heterostructures
2018
This paper reports on the modification of the sheet resistance under Ti/Al/Ni/Au Ohmic contacts on AlGaN/GaN heterostructures, studied by means of Transmission Line Model (TLM) structures, morphological and structural analyses, as well as computer simulations. In particular, the contacts exhibited an Ohmic behaviour after annealing at 800 degrees C, with a specific contact resistance rho(c) = (2.4 +/- 0.2) x 10(-5) Omega cm(2), which was associated to morphological and structural changes of both the metal layer and the interface. Interestingly, TLM analyses gave a value of the sheet resistance under the contact (R-SK = 26.1 +/- 5.0 Omega/rectangle) significantly lower than that measured out…
Spin-Polarized Scanning Tunnelling Microscopy of Ultrathin Films
2006
Using low temperature spin-polarized scanning tunneling microscopy we have studied the morphology and magnetic properties of ultrathin Fe(0.5 ML)Au(0.5 ML) nanowires prepared on a Mo(110) single crystal. The Fe nanostripes grown by step flow on a Mo(110) at 700 K were covered by Au at RT, and subsequently annealed at 700 K. Differences in the morphology of Au on Fe(110)/Mo(110) and clean Mo(110) surfaces are observed and discussed. After annealing, the Mo is covered by a homogeneous FeAu ML alloy with several iron enriched islands which reveal an out-of-plane magnetic contrast. Direct lateral exchange coupling has been observed for these islands.
Influence of Co content on structural and magnetic properties of CoxFe84−xNb7B9 alloys
2003
Nanocrystallization of CoxFe84� xNb7B9 (x ¼ 17; 25, 33) alloys has been studied. Crystallization of specimens starts above 4501C. After annealing of specimens in the range 500–7001C, apart from amorphous component and BCC Fe-Co alloy, a non-magnetic component also appears, which is attributed to (Fe1� xCox)2Nb phase with a relative area of about 14%. Decrease of quadrupole splitting with annealing temperature indicates some possible ordering of the nonmagnetic phase. r 2002 Elsevier Science B.V. All rights reserved.