20 research outputs found
RF Power Effect On Structural Characteristics Of Amorphous Carbon Nitride Thin Films Deposited By Reactive Radiofrequency Sputtering
Amorphous carbon nitride thin films were deposited, at room temperature, on silicon substrates by reactive radiofrequency (RF) sputtering from a graphite target in an atmosphere of nitrogen. The structural properties were investigated by Raman spectroscopy. This spectroscopy reveals the presence of C–C, C=C, C=N and C≡N bonding types. The Raman intensity (ID/IG) ratio of disorder and graphitic bands increased from 1.29 to 2.67 with increasing the RF power from 100 to 400W indicating an increase of structural disorder.Amorphous carbon nitride thin films were deposited, at room temperature, on silicon substrates by reactive radiofrequency (RF) sputtering from a graphite target in an atmosphere of nitrogen. The structural properties were investigated by Raman spectroscopy. This spectroscopy reveals the presence of C–C, C=C, C=N and C≡N bonding types. The Raman intensity (ID/IG) ratio of disorder and graphitic bands increased from 1.29 to 2.67 with increasing the RF power from 100 to 400W indicating an increase of structural disorder
Structural and chemical properties of RF sputtered a-C/WOx bilayers
Amorphous carbon on tungsten oxide (a-C/WOx) bilayers were deposited, on glass and silicon substrates, by radio-frequency (RF) sputtering. The WOx layers are obtained from a pure tungsten target in a mixture of argon and oxygen while the a-C ones were obtained from a pure graphite target in a pure argon plasma. The structural and chemical properties of the a-C/WOx interface were investigated by Grazing Incidence X-Ray Diffraction (GIXRD), X-Ray Reflectometry (XRR) and Electron Dispersive Analysis of X-Ray (EDAX). The XRR spectra show that the a-C/WOx interface is strongly reactive, for high RF powers, with the formation of an inhomogeneous WOxCy total layer. The density of this layer is much smaller than the WOx one. For low RF powers, the a-C/WOx interface is also reactive and the total layer obtained is inhomogeneous in depth but the W atoms content in the top layer is relatively small. This result is also confirmed by the EDAX analyses. The GIXRD spectra show that the WOx layers are crystallized while there is no formation of crystallized tungsten carbides or oxycarbides.Amorphous carbon on tungsten oxide (a-C/WOx) bilayers were deposited, on glass and silicon substrates, by radio-frequency (RF) sputtering. The WOx layers are obtained from a pure tungsten target in a mixture of argon and oxygen while the a-C ones were obtained from a pure graphite target in a pure argon plasma. The structural and chemical properties of the a-C/WOx interface were investigated by Grazing Incidence X-Ray Diffraction (GIXRD), X-Ray Reflectometry (XRR) and Electron Dispersive Analysis of X-Ray (EDAX). The XRR spectra show that the a-C/WOx interface is strongly reactive, for high RF powers, with the formation of an inhomogeneous WOxCy total layer. The density of this layer is much smaller than the WOx one. For low RF powers, the a-C/WOx interface is also reactive and the total layer obtained is inhomogeneous in depth but the W atoms content in the top layer is relatively small. This result is also confirmed by the EDAX analyses. The GIXRD spectra show that the WOx layers are crystallized while there is no formation of crystallized tungsten carbides or oxycarbides
Grazing incidence X-rays reflectometry and diffraction studies of radiofrequency sputter deposited a-C/W interfaces
Amorphous carbon on tungsten (a-C/W) bi-layers have been deposited, on crystalline silicon substrates, by Radio-Frequency (RF) sputtering. Carbon films were deposited, from a high purity graphite target, with a RF power of 250 Watts; while those of tungsten were obtained, from a pure tungsten target, at two different RF powers of 100 and 200 Watts. Annealing effects, at 1000 K in vacuum, on the structure and the interface state of the samples, were studied by Grazing Incidence X-rays Reflectometry (GIXR) and Diffraction (GIXD) techniques. The GIXR measurements show that the raw a-C/W interfaces are abrupt while the annealed ones are diffuse with formation of a W2C interfacial layer. The GIXD measurements reveal that W films deposited at 100 Watts are amorphous whereas those deposited at 200 Watts are polycrystalline in the b-W phase. After annealing at 1000 K, the formation of W2C at the a-C/W interfaces is confirmed by GIXD measurements. The W2C content is more important in the case of the W layer deposited at 200 Watts. Moreover, the part of the W layer, which has not reacted with the a-C layer, is crystallized in the α-W phase after the annealing.Amorphous carbon on tungsten (a-C/W) bi-layers have been deposited, on crystalline silicon substrates, by Radio-Frequency (RF) sputtering. Carbon films were deposited, from a high purity graphite target, with a RF power of 250 Watts; while those of tungsten were obtained, from a pure tungsten target, at two different RF powers of 100 and 200 Watts. Annealing effects, at 1000 K in vacuum, on the structure and the interface state of the samples, were studied by Grazing Incidence X-rays Reflectometry (GIXR) and Diffraction (GIXD) techniques. The GIXR measurements show that the raw a-C/W interfaces are abrupt while the annealed ones are diffuse with formation of a W2C interfacial layer. The GIXD measurements reveal that W films deposited at 100 Watts are amorphous whereas those deposited at 200 Watts are polycrystalline in the -W phase. After annealing at 1000 K, the formation of W2C at the a-C/W interfaces is confirmed by GIXD measurements. The W2C content is more important in the case of the W layer deposited at 200 Watts. Moreover, the part of the W layer, which has not reacted with the a-C layer, is crystallized in the α-W phase after the annealing
Dielectric and relaxation studies in hydrothermal processed PLZT ceramics
(Pb1-yLay)(Zr0.52Ti0.48)O3 (PLZTy) powders were prepared using hydrothermal process and their structural and dielectric properties investigated. Increasing La content is shown to enhance crystallization of the raw samples and to transform the average symmetry to tetragonal one in the calcined ones. Two anomalies are observed on the real part of the permittivity on the sample with y = 0.03, at a relatively high temperatures (~ 180 °C, ~ 260 °C). The latter was interpreted as a transition from ferroelectric-rhombohedral phase to ferroelectric-quadratic phase. A quadratic law in temperature was used to study the temperature dependence of the dielectric constant of the samples showing the relaxation phenomenon and values of the fitting parameters such as the diffuseness parameter were calculated and discussed.(Pb1-yLay)(Zr0.52Ti0.48)O3 (PLZTy) powders were prepared using hydrothermal process and their structural and dielectric properties investigated. Increasing La content is shown to enhance crystallization of the raw samples and to transform the average symmetry to tetragonal one in the calcined ones. Two anomalies are observed on the real part of the permittivity on the sample with y = 0.03, at a relatively high temperatures (~ 180 °C, ~ 260 °C). The latter was interpreted as a transition from ferroelectric-rhombohedral phase to ferroelectric-quadratic phase. A quadratic law in temperature was used to study the temperature dependence of the dielectric constant of the samples showing the relaxation phenomenon and values of the fitting parameters such as the diffuseness parameter were calculated and discussed
Optical Emission Spectroscopy Study Of RF Sputtered A-C/WOX Interface
Amorphous carbons on tungsten oxide (a-C/WOX) bi-layers were deposited on silicon substrates by rf sputtering. The WOX layers were obtained from a pure tungsten target, in a gas mixture of argon and oxygen, whereas those of a-C were obtained from a graphite target, in pure argon plasma. The reactivity of the a-C/WOX interface and the ion bombardment effects have been studied by Optical Emission Spectroscopy (OES) technique. The OES spectra show that the a-C/WOX interface is reactive in accordance with previous results obtained by X-ray reflectometry. The inter-diffusion depth is estimated to be greater than 56 nm. Emission lines of W are still observed even after an ion bombardment time of about 45 minutes. This result confirms the presence of the Knock-on effect.Amorphous carbons on tungsten oxide (a-C/WOX) bi-layers were deposited on silicon substrates by rf sputtering. The WOX layers were obtained from a pure tungsten target, in a gas mixture of argon and oxygen, whereas those of a-C were obtained from a graphite target, in pure argon plasma. The reactivity of the a-C/WOX interface and the ion bombardment effects have been studied by Optical Emission Spectroscopy (OES) technique. The OES spectra show that the a-C/WOX interface is reactive in accordance with previous results obtained by X-ray reflectometry. The inter-diffusion depth is estimated to be greater than 56 nm. Emission lines of W are still observed even after an ion bombardment time of about 45 minutes. This result confirms the presence of the Knock-on effect
Proton conductivity in Al-stevensite pillared clays
Fine stevensite mineral fraction (< 2 m) has been extracted from natural Moroccan ghassoulite clay. Thereafter, it has been pillared by Al13 polycations species. Physico-chemical characterization, performed using X-ray diffraction (XRD), thermal analysis (TG-TDA) and Scanning Electron Microscopy (SEM) equipped with X-ray Energy Dispersion (XED) analysis, has proved that stevensite pillaring has been successfully achieved. Electrical impedance measurements, carried out onto samples before and after pillaring operation, have shown an increase in proton conductivity for pillared with respect to pristine stevensite clay mineral.Fine stevensite mineral fraction (< 2 m) has been extracted from natural Moroccan ghassoulite clay. Thereafter, it has been pillared by Al13 polycations species. Physico-chemical characterization, performed using X-ray diffraction (XRD), thermal analysis (TG-TDA) and Scanning Electron Microscopy (SEM) equipped with X-ray Energy Dispersion (XED) analysis, has proved that stevensite pillaring has been successfully achieved. Electrical impedance measurements, carried out onto samples before and after pillaring operation, have shown an increase in proton conductivity for pillared with respect to pristine stevensite clay mineral
Characterization of CuInTe2 thin films prepared by flash evaporation
peer reviewedThin films of CuInTe2 were grown by flash evaporation. The influence of the substrate temperature Ts during film deposition on the properties of the thin films was examined. CuInTe2 films were structurally characterized by the grazing incidence x-ray diffraction (GIXD) technique. Investigation by this technique demonstrates that the surface of thin films of CuInTe2 prepared by flash vaporation at Ts > 100 °C exhibits the chalcopyrite structure with additional binary compounds in the surface. However, in the volume the films exhibit the chalcopyrite structure only; no foreign phases were observed. X-ray reflectometry was utilized to evaluate the critical reflection angle bc of CuInTe2 (bCuInTe2 c 0.32°) which permitted us to calculate the density of the films to be 6 g cm−3. The evaporated films were p type and the films deposited at Ts = 100 °C had a resistivity in the range 0.3–2 cm. From optical measurements we have determined the optical energy gap Eg 0.94 eV and the effective reduced mass m*r 0.07me
Abiotic ammonium formation in the presence of Ni-Fe metals and alloys and its implications for the Hadean nitrogen cycle
Experiments with dinitrogen-, nitrite-, nitrate-containing solutions were conducted without headspace in Ti reactors (200°C), borosilicate septum bottles (70°C) and HDPE tubes (22°C) in the presence of Fe and Ni metal, awaruite (Ni80Fe20) and tetrataenite (Ni50Fe50). In general, metals used in this investigation were more reactive than alloys toward all investigated nitrogen species. Nitrite and nitrate were converted to ammonium more rapidly than dinitrogen, and the reduction process had a strong temperature dependence. We concluded from our experimental observations that Hadean submarine hydrothermal systems could have supplied significant quantities of ammonium for reactions that are generally associated with prebiotic synthesis, especially in localized environments. Several natural meteorites (octahedrites) were found to contain up to 22 ppm Ntot. While the oxidation state of N in the octahedrites was not determined, XPS analysis of metals and alloys used in the study shows that N is likely present as nitride (N3-). This observation may have implications toward the Hadean environment, since, terrestrial (e.g., oceanic) ammonium production may have been supplemented by reduced nitrogen delivered by metal-rich meteorites. This notion is based on the fact that nitrogen dissolves into metallic melts