Search results for "Annealing"
showing 10 items of 434 documents
Influence of nanoscale order–disorder transitions on the magnetic properties of Heusler compounds for spintronics
2017
Modifications in nanoscale chemical order are used to tune the magnetic properties, namely T-C, of Co2FeSixAl1-x (0 < x < 1). High-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) with Z-contrast reveals nanoscale regions of L2(1) order within a B2 matrix in the off-stoichiometry samples. Perhaps surprisingly, the latter, more chemically disordered structure, exhibits a higher T-C. Upon annealing, the off-stoichiometry samples become more homogeneous with the fraction of L2(1) order decreasing. The short-range order was also investigated using X-ray absorption fine structure (XAFS) measurements at the Co and Fe K edges. Since the local atomic environments of C…
The effect of annealing temperature and time on synthesis of graphene thin films by rapid thermal annealing
2015
In this paper, we performed synthesis of graphene thin films by rapid thermal annealing (RTA) of thin nickel copper (Ni/Cu) layers deposited on spectroscopic graphite as a carbon source. Furthermore, we investigated the effect of annealing temperature and annealing time on formation and quality of synthesized graphene films. Raman spectroscopy study showed that annealing at lower temperatures results in formation of monolayer graphene films, while annealing at higher temperatures results in formation of multilayer graphene films. We used Raman mapping to determine the distribution of graphene sheets. Surface morphology of graphene thin films was investigated by atomic force microscopy and s…
Tailoring of highly porous SnO2 and SnO2-Pd thin films
2019
Abstract Tin oxide is a material that attracts attention due to variety of technological applications. The main parameters that influence its properties are morphology, crystalline structure and stoichiometry. Researchers try to develop nanostructured thin films with tunable parameters that would conform its technological applications. Herein, we report on the preparation and characterization of highly porous SnO2 and Pd-doped SnO2 thin films. These films were deposited in the form of nanorods with controllable geometry. Such morphology was achieved by utilizing glancing angle deposition (GLAD) with assisted magnetron sputtering. This arrangement allowed preparation of slanted pillars, zig-…
CFD prediction of bubble behavior in two-dimensional gas-solid fluidized beds
2009
This work focuses on the computational fluid dynamics (CFD) simulation of a laboratory-scale, two-dimensional fluidized bed and the relevant experiments in order to validate the prediction capability of the adopted codes and models. Both experimental and computational quantitative data were analyzed by means of an original digital image analysis technique, allowing for coherent comparison of computational and experimental results. In particular, this work analyzes the capability of the CFD simulations in predicting the fluctuating behavior of bubbling fluidized beds by means of frequency analysis of bubble-related phenomena.
Selective growth and optical properties of sputtered BaTiO3films
2000
we report the growth of BaTiO 3 thin films by standard Radio Frequency sputtering. Without any in situ or post annealing, these polycristalline films are oriented relative to the substrate even when it is amorphous. We show that this preferential orientation may be monitored using a DC Bias during the film growth. At room temperature, cubic films of (100) and (110) orientations have been achieved, on fused silica substrate. Some optical waveguiding properties of these films have been studied. The resulting film index is 2.26 and the optical step index at the substrate interface is sharp. This allows the use of standard RF sputtering techniques to monitor oriented BaTiO 3 films for linear op…
Cu cluster shell structure at elevated temperatures
1991
Equilibrium structures of small (3--29)-atom Cu clusters are determined by simulated annealing, and finite-temperature ensembles are simulated by Monte Carlo techniques using the effective-medium theory for the energy calculation. Clusters with 8, 18, and 20 atoms are found to be particularly stable. The equilibrium geometrical structures are determined and found to be determined by a Jahn-Teller distortion, which is found to affect the geometry also at high temperatures. The ``magic'' clusters retain their large stability even at elevated temperatures.
Substrate and atmosphere influence on oxygen p-doped graphene
2016
Abstract The mechanisms responsible for p-type doping of substrate supported monolayer graphene (Gr) by thermal treatments in oxygen ambient have been investigated by micro-Raman spectroscopy, atomic force microscopy (AFM) and X-ray Photoelectron Spectroscopy (XPS), considering commonly employed dielectric substrates, such as SiO 2 and Al 2 O 3 thin films grown on Si. While a high p-type doping (∼10 13 cm −2 ) is observed for Gr on SiO 2 , no significant doping is found for Gr samples on the Al 2 O 3 substrate, suggesting a key role of the Gr/SiO 2 interface states in the trapping of oxygen responsible for the Gr p-type doping. Furthermore, we investigated the doping stability of Gr on SiO…
Highly Stable Thin Films Based on Novel Hybrid 1D (PRSH)PbX3 Pseudo-Perovskites
2021
In this study, the structure and morphology, as well as time, ultraviolet radiation, and humidity stability of thin films based on newly developed 1D (PRSH)PbX3 (X = Br, I) pseudo-perovskite materials, containing 1D chains of face-sharing haloplumbate octahedra, are investigated. All films are strongly crystalline already at room temperature, and annealing does not promote further crystallization or film reorganization. The film microstructure is found to be strongly influenced by the anion type and, to a lesser extent, by the DMF/DMSO solvent volume ratio used during film deposition by spin-coating. Comparison of specular X-ray diffraction and complementary grazing incidence X-ray diffract…
Thermal atomic layer deposition of AlOxNy thin films for surface passivation of nano-textured flexible silicon
2019
Abstract Aluminum oxynitride (AlOxNy) films with different nitrogen concentration are prepared by thermal atomic layer deposition (ALD) for flexible nano-textured silicon (NT-Si) surface passivation. The AlOxNy films are shown to exhibit a homogeneous nitrogen-doping profile and the presence of an adequate amount of hydrogen, which is investigated by Time-of-Fight Elastic Recoil Detection Analysis (ToF-ERDA). The effective minority carrier lifetimes are measured after the NT-Si surface passivation; the minimum surface recombination velocity (SRV) of 5 cm-s−1 is achieved with the AlOxNy film in comparison to the Al2O3 and AlN films (SRV of 7–9 cm-s−1). The better SRV with AlOxNy film is due …
Structural organization of silanol and silicon hydride groups in the amorphous silicon dioxide network
2011
We present a study on the effects of an isothermal annealing treatment on a-SiO 2 having a significant content of silanol hydride groups (Si-H). We examined the properties of the IR absorption bands of silanol (Si-OH) and silicon hydride groups as a function of the duration of the thermal treatment. We showed that the Si-OH and Si-H groups contents decrease in a linearly correlated way. The annealing dynamics suggest that the two species are close to each other in the amorphous network. We showed that the profile of the silanol groups absorption band is the same as that observed in other commercial a-SiO 2 materials, irrespectively of the concomitant presence of nearby Si-H groups, and, mor…