Search results for "chemical vapor deposition"
showing 10 items of 199 documents
Studies on atomic layer deposition of MOF-5 thin films
2013
International audience; Deposition of MOF-5 thin films from vapor phase by atomic layer deposition (ALD) was studied at 225-350 degrees C. Zinc acetate (ZnAc2) and 1,4-benzenedicarboxylic acid (1,4-BDC) were used as the precursors. The resulting films were characterized by UV-Vis spectrophotometry, Fourier transform infrared spectroscopy (FTIR), optical microscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), time-of-flight elastic recoil detection analysis (TOF-ERDA), isopropanol adsorption tests, and nanoindentation. It was found out that the as-deposited films were amorphous but crystallized in humid conditions at room temperature. The crystalline films h…
Raman imaging and spectroscopy of heterogeneous individual carbon nanotubes
2003
Isolated single-walled carbon nanotubes (CNTs) were grown by chemical vapor deposition methods on Fe/Mo/Al2O3 catalysts, which were patterned by microcontact printing. The pattern allowed us to trace back and investigate the same isolated CNT by atomic-force (AFM) and confocal Raman microscopy with different excitation wavelengths. A change of the Raman intensity could be correlated with structural defects revealing that the molecular structure of the tubes is changing along the tube axis. By investigating the same tube segments with different excitation energies, we found that the D-line of isolated tubes shows a strong dispersive effect of 45−50 cm-1/eV. In contrast, the spectral position…
Conductimetry and impedance spectroscopy study of low pressure metal organic chemical vapor deposition TiN O films as a function of the growth temper…
2001
Abstract Titanium oxinitride thin films have been grown by low pressure metal organic chemical vapor deposition (LP-MOCVD) using titanium isopropoxide, Ti(OCH(CH 3 ) 2 ) 4 (TIP) and NH 3 precursors in a growth temperature range from 450 to 750°C on sapphire substrates. The electrical behaviour of these films was studied between 400 and 173 K, revealing three different behaviours, ranking from a hopping conductivity (450–500°C) to a conducting one (700–750°C), with a dual behaviour for the intermediate growth temperatures. Moreover, at room temperature, both conductimetry and impedance spectroscopy highlighted a percolation behaviour, interpreted in terms of continuum percolation. The effect…
Temperature and substrate influence on the structure of TiN O thin films grown by low pressure metal organic chemical vapour deposition
2000
Abstract This paper presents the growth and characterization of titanium oxinitride (TiN x O y ) films grown by low pressure metal organic chemical vapour deposition (LP-MOCVD). The film nitrogen content, obtained by Rutherford backscattering spectroscopy (RBS), increases as the growth temperature increases (from 23 at.% at 450°C to 46 at.% at 750°C). Below 550°C, the films do not show any X-ray diffraction pattern. Above 550°C, the deposited films present the (111) and (200) TiN textures. Films deposited on (100) Si exhibit a 2 θ shift to higher Bragg angles, depending on the N/O ratio. These shifts are explained by using a substitutional oxygen model. Moreover, the atomic structure of suc…
Antiferromagnetism and p‐type conductivity of nonstoichiometric nickel oxide thin films
2020
Plasma‐enhanced atomic layer deposition was used to grow non‐stoichiometric nickel oxide thin films with low impurity content, high crystalline quality, and p‐type conductivity. Despite the non‐stoichiometry, the films retained the antiferromagnetic property of NiO.
High temperature reactivity of nickel aluminide diffusion coatings
2008
Abstract The high-temperature oxidation behaviour of nickel aluminides has been studied at 900 °C in air under atmospheric pressure. Yttria doped and undoped specimens of nickel were aluminised and then oxidised for 100 h under isothermal and cycling conditions. The results showed that when yttria is added by metal-organic chemical vapour deposition technique prior to the aluminisation process, it increased the oxidation rate of aluminised nickel, but improved the oxide scale adherence under cyclic conditions. The effects of yttria on the scale morphology, oxidation behaviour and scale spallation tendency are discussed based on the experimental results, using X-ray diffraction (XRD), scanni…
Cathodoluminescence and structural studies of nitrided 3D gallium structures grown by MOCVD
2009
Abstract Cathodoluminescence (CL) spectrum imaging and grazing incidence X-ray diffraction (GIXRD) are employed to investigate nitride three-dimensional (3D) gallium structures. The metallic precursors are naturally obtained on a large variety of substrates by metal-organic chemical vapor deposition (CVD) with different shape/size controlled by the growth conditions, especially the temperature. These 3D metallic structures are subsequently exposed to a nitridation process in a conventional CVD reactor to form GaN nanocrystals, as confirmed by GIXRD measurements. CL spectroscopy shows visible light emission (2.5–2.8 eV) excited from the GaN in the 3D structures.
Synthesis of nanostructured amorphous carbon-copper composite films by plasma-enhanced chemical vapour deposition
2016
Abstract Nanostructured amorphous carbon-copper composite films were formed by plasma-enhanced chemical vapour deposition. The formation was done on copper-silicon substrates at 25 °C, 300 °C, 520 °C, and 700 °C temperatures using an acetylene gas at 40–70 Pa pressure. The heating of the Cu Si substrate induced formation of Cu nanospheres with 50–500 nm size depending on the substrate temperature. The microstructure and composition of nanostructured carbon-copper composite films were investigated. The SEM views showed formation of amorphous carbon films with the randomly distributed nanostructures. The oxygen concentration in the composite films decreased with the increased heating temperat…
Hysteresis in graphene nanoribbon field-effect devices
2020
Hysteresis in the current response to a varying gate voltage is a common spurious effect in carbon-based field effect transistors. Here, we use electric transport measurements to probe the charge transport in networks of armchair graphene nanoribbons with a width of either 5 or 9 carbon atoms, synthesized in a bottom-up approach using chemical vapor deposition. Our systematic study on the hysteresis of such graphene nanoribbon transistors, in conjunction with temperature-dependent transport measurements shows that the hysteresis can be fully accounted for by trapping/detrapping carriers in the SiO2 layer. We extract the trap densities and depth, allowing us to identify shallow traps as the …
Growth and characterization of AP-MOCVD iron doped titanium dioxide thin films
1999
Abstract Atmospheric pressure metal organic chemical vapor deposition (AP-MOCVD) was used to prepare iron doped titanium dioxide thin films. Thin films, between 40 and 150 nm thick, were deposited on Si, SiO 2 and Al 2 O 3 substrates using titanium tetra isopropoxide and ferrocene as metal organic precursors. TiO 2 iron doping was achieved in the range of 1–4 at.%. The film morphology and thickness, polycrystalline texture and doping content were studied using respectively scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The influence of growth temperature, deposition time, substrate type and dopant partial pressure were studied. Electr…