Search results for "Vapor deposition"
showing 10 items of 229 documents
In Situ Heating TEM Study of Onion-like WS2 and MoS2 Nanostructures Obtained via MOCVD
2007
We report on the in situ heating transmission electron microscopy (TEM) study of WS2 and MoS2 nanoparticles obtained from metal–organic chemical vapor deposition (MOCVD). The general behavior of MoS2 and WS2 is similar: Round, amorphous particles in the pristine sample transform to hollow, onion-like particles upon annealing. A second type of particle with straight layers exhibits only minor changes. A significant difference between both compounds could be demonstrated in their crystallization behavior. The results of the in situ heating experiments are compared to those obtained from an ex situ annealing process under Ar.
Absorption and luminescence in amorphous SixGe1-xO2 films fabricated by SPCVD
2012
Abstract Optical absorption and photoluminescence of Ge-doped silica films fabricated by the surface-plasma chemical vapor deposition (SPCVD) are studied in the 2–8 eV spectral band. The deposited on silica substrate films of about 10 μm in thickness are composed as x·GeO2-(1-x)·SiO2 with x ranging from 0.02 to 1. It is found that all as‐deposited films do not luminesce under the excitation by a KrF (5 eV) excimer laser, thus indicating lack of oxygen deficient centers (ODCs) in them. After subsequent fusion of silicon containing (x
The Effect of surface topographical changes of two different surface treatments rotary instrument
2018
Background One of the major innovations in endodontics has been the introduction of nickel-titanium (NiTi) alloy. This study evaluated the surface topographical changes of two different surface treatments rotary instrument after instrumentation and sterilization. Material and Methods 240 Extracted teeth were included in this study. 90 new AlphaKite and Revo-S NiTi rotary instruments were selected and divided into two groups (Group A 45 AlphaKite and group B 45 Revo-S). Each group were divided into three subgroups: (A1, B1) n=5 files were used as a control, (A2,B2) n=20 files were used to prepare three root canals using endodontic rotary motor then sterilized by autoclave for one cycle under…
Ge-doped silica nanoparticles: production and characterisation
2016
Silica nanoparticles were produced from germanosilicate glasses by KrF laser irradiation. The samples were investigated by cathodoluminescence and scanning electron microscopy, providing the presence of nanoparticles with size from tens up to hundreds of nanometers. The emission of the Germanium lone pair center is preserved in the nanoparticles and atomic force microscopy revealed the presence of no spherical particles with a size smaller than ~4 nm. The absorption coefficient enhancement induced by Ge doping is reputed fundamental to facilitate the nanoparticles production. This procedure can be applied to other co-doped silica materials to tune the nanoparticles features.
Structural studies of nano/micrometric semiconducting GaInP wires grown by MOCVD
2004
Abstract 3D (Ga,In)/GaInP structures were grown on polycrystalline InP substrates by the MOCVD technique. The growth temperature was varied from 600 to 700 °C. Trimethyl-gallium and N 2 were, respectively, used as the Ga source and the carrier gas. These newly presented 3D structures have a scepter-like shape and are composed of a long GaInP internal support (rods of tens of μm long and tens of nm diameter) capped by a micrometer size metallic (Ga,In) structure. These structures were characterized by the SEM, EDX and TEM techniques. High-resolution TEM shows that the support rods present a GaInP single crystal structure. A preliminary discussion about the growth step mechanism, based on the…
Growth of nanometric CuGaxOystructures on copper substrates
2005
This paper presents an alternative method based on the metal–organic chemical vapour deposition technique to obtain new nanowire structures. Here, the metal–organic precursor acts as a catalyst and interacts with a metallic substrate to produce 3D structures such as nanowires. In the present case, trimethyl gallium interacts with a copper metallic substrate to build a single-crystalline CuGaxOy wire structure. Electronic microscopy techniques on image or diffraction modes have provided the structural and chemical characterization of the obtained nanowires.
Soft X-ray photoelectron microscopy used for the characterization of diamond, a-C and CN , thin films
2002
Abstract This article gives an overview about the application of X-ray photoemission electron microscopy (X-PEEM) used for the analysis of carbon thin films. We present the results of an X-ray absorption near edge structure (XANES) study of CVD diamond, a-C and CNx films on Si (100) as well as a defect analysis of a hard disc scratch test. The sp2/sp3 ratio of the carbon films was determined and mapped in the electron micrographs, which show localized defects in the surface.
High-Mobility, Wet-Transferred Graphene Grown by Chemical Vapor Deposition
2019
We report high room-temperature mobility in single layer graphene grown by Chemical Vapor Deposition (CVD) after wet transfer on SiO$_2$ and hexagonal boron nitride (hBN) encapsulation. By removing contaminations trapped at the interfaces between single-crystal graphene and hBN, we achieve mobilities up to$\sim70000cm^2 V^{-1} s^{-1}$ at room temperature and$\sim120000cm^2 V^{-1} s^{-1}$ at 9K. These are over twice those of previous wet transferred graphene and comparable to samples prepared by dry transfer. We also investigate the combined approach of thermal annealing and encapsulation in polycrystalline graphene, achieving room temperature mobilities$\sim30000 cm^2 V^{-1} s^{-1}$. These …
Study of the Chemical Conversion of Aluminum Alloys by Coupling CFDE and EQCM
2004
The ability of the channel flow double electrode (CFDE) technique and electrochemical quartz crystal microbalance (EQCM) for studying in situ chromate phosphate conversion coating on 5182 aluminum alloys was explored. It was first demonstrated that aqueous Cr(VI) can be analyzed quantitatively with the CFDE technique by reduction into Cr(III) on a graphite electrode. Samples used for EQCM were quartz plated by physical vapor deposition using a 5182 alloy target, allowing thin layers of aluminum alloys with a similar chemical composition to be obtained. EQCM was adapted in order to account for the hydrodynamic conditions in an industrial process, by placing the quartz in a flow cell. In orde…
In-Situ Growth of Ultrathin Films of NiFe-LDHs: Towards a Hierarchical Synthesis of Bamboo-Like Carbon Nanotubes
2014
The synthesis of ultrathin films (UTFs) of NiFe-LDHs has been achieved by means of an in situ hydrothermal approach, leading to a flat disposition of the LDH crystallites on the substrate, in clear contrast to the most common perpendicular orientation reported to date. Experimental factors like time of synthesis or the nature of the substrate, seem to play a crucial role during the growing process. The 2D morphology of the NiFe-LDH crystallites was kept after a calcination procedure, leading to a topotactic transformation into mixed-metal oxide platelets. Hereby, in order to study the catalytic behavior of our samples, a chemical vapor deposition process is explored upon the as-synthesized …