144 research outputs found
LOW-TEMPERATURE SILICON CRYSTALLIZATION MEDIATED BY COPPER SILICIDE FORMATION IN CU/A-SI-H BILAYERS
No full textCu/a-Si:H interfacial reaction and copper silicide mediated crystallization of amorphous silicon have been investigated by a combination of several analytical techniques: atomic force microscopy, scanning electron microscopy, Raman spectroscopy through a microscope probe, Auger electron spectroscopy and nuclear analysis. Si crystallization has been evidenced in samples annealed at 280 degrees C, while the formation of copper silicide occurs at 200 degrees C. The role of hydrogen in the crystallization process is discussed
IN-DEPTH MODIFICATIONS OF IMPLANTED AMORPHOUS-CARBON FILMS
No full textAmorphous carbon films (a-C:H) and nitrogen incorporated carbon films [a-C:H(N)] deposited by a self-bias glow discharge have been implanted with 70 keV nitrogen ions at fluences of 0.6, 1 and 2 x 10(17) N/cm(2) The in-depth modifications caused by ion implantation were determined by means of nuclear techniques, such as Rutherford Backscattering Spectrometry (RBS), Nuclear Reaction Analysis (NRA) and Elastic Recoil Detection Analysis (ERDA), as well as by Auger Electron Spectroscopy (AES) and Raman scattering. ERDA profiles show that nitrogen implantation causes hydrogen depletion, the amount of which depends on the film composition and on the ion fluence. In a-C:H(N) films nitrogen loss was also measured. The induced structural modifications in both a-C:H and a-C:H(N) films were followed by both AES, using factor analysis, and microprobe Raman spectroscopy. They turn out to be related to the energy deposited by the incident ions. Our results indicate that the ion-beam bombardment causes in both a-C:H and a-C:H (N) films an increase of either the degree of disorder or the ratio between sp(2)/sp(3) bonds across the hydrogen-depleted layer, which depends on the ion fluence
RAMAN-SPECTROSCOPY ON NITROGEN-INCORPORATED AMORPHOUS HYDROGENATED CARBON-FILMS
No full textNitrogenated a-C:H films, a-C:H(N), were obtained by plasma decomposition of methane-nitrogen mixtures. The samples were thermally annealed in vacuum for 30 min at fixed temperatures between 300 and 700-degrees-C. Undoped films were implanted at room temperature with 70 keV-N+ at fluences of 6, 10 and 20 x 10(16) N cm-2. The induced structural modifications were studied by Raman spectroscopy through the evolution of the D and G bands. The spectral evolution observed on a-C:H(N) samples shows evidence that a progressive graphitization follows the nitrogen incorporation in these films. Micro-Raman depth profile analysis indicates that the structural and modifications observed on implanted samples are due to the energy deposited by the incident ions. Thermal annealing induces the formation of graphitic domains in a-C:H(N) films
AMORPHOUS NITROGENATED CARBON-FILMS - STRUCTURAL MODIFICATIONS INDUCED BY THERMAL ANNEALING
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STRUCTURAL MODIFICATIONS IN A-C-H FILMS DOPED AND IMPLANTED WITH NITROGEN
No full textThe results of a study on structural modifications resulting from nitrogen incorporation into hard amorphous, hydrogenated carbon (a-C:H) films are presented. Nitrogen-doped films are produced by r.f. glow discharge deposition from CH4-N-2 mixtures onto silicon substrates or by 70 keV nitrogen ion implantation of a-C:H films. The Films were obtained at different N-2, partial pressures (P-N2=0%-50%) and bias voltages (V-b=-200 to -900 V), with a total pressure of P=8 Pa. The ion-implanted films were obtained at fluences of 4-20 x 10(16) N cm(-2). The samples were characterized by nuclear techniques (Rutherford backscattering, elastic recoil detection and nuclear reaction analysis), Raman scattering, Auger electron spectroscopy and the gas effusion method. It has been observed that nitrogen incorporation during deposition does not change the atomic density or hydrogen concentration, although the internal stress is reduced by about 40%. For the implanted samples, a depletion of hydrogen can be determined. The thickness of this depletion layer is of the order of R(p). The internal stress is reduced by a factor of 5 and this is associated with the formation of an interconnected void structure
STUDY OF ANNEALED AMORPHOUS HYDROGENATED FILMS BY ELASTIC RECOIL DETECTION ANALYSIS
No full textHydrogen out-diffusion in amorphous hydrogenated films, a-Ge:D, a-C:H and a-C:H(N) films, was studied by using elastic recoil detection analysis (ERDA). The a-Ge:D films were deposited onto Si substrates at 210-degrees-C by rf-sputtering in an atmosphere of argon and deuterium. The a-C:H and a-C:H(N) films produced by plasma decomposition of a methane-nitrogen mixture, were deposited onto Si substrates at room-temperature. The a-Ge:D samples were annealed in nitrogen atmosphere at temperatures between 200 and 400-degrees-C and the carbon films in a vacuum furnace, with the temperature ranging from 300 to 700-degrees-C. The total hydrogen (deuterium) content and the concentration depth-profiles were determined by ERDA using helium beams of 2.2 and 3.0 MeV for hydrogen and deuterium profiles, respectively. Two kinds of hydrogen motion coexist in a-Ge:D films: a fast one, probably due to the presence of a network of interconnected voids, and a slower one, due to the dispersive-like diffusion of atomic deuterium in the amorphous skeleton. In a-C:H and a-C:H(N) films only the fast process was observed. A correlation between hydrogen loss and structural modifications of annealed carbon films was also made
NITROGEN IMPLANTATION INTO AMORPHOUS-CARBON FILMS - XPS, AES AND RAMAN ANALYSES
No full textHard amorphous hydrogenated carbon films (350 nm thick) deposited by self-bias glow discharge were implanted at room temperature with 70 keV nitrogen ions at fluences of 0.6, 1.0 and 2.0 X 10(17) N/cm(2). The implanted energy was chosen so that the projected range plus straggling (R(p) + Delta R(p)) was smaller than the film thickness. The implanted samples were analyzed by Auger electron spectroscopy, X-ray photoelectron spectroscopy and micro-Raman spectroscopy. Factor analysis was applied to the crater-edge Auger profile. For micro-Raman depth profiles, a well focused argon laser beam was scanned across the wall of the same crater produced by 2 keV Ar+ bombardment for the AES measurements. XPS depth profiles were also obtained. The Auger and Raman results indicated that the structural modifications (increase of the relative amount of carbon sp(2)-bonds) are related to the energy deposited by the incident ion and depend on the ion fluence. Nitrogen incorporation into the amorphous carbon network can be inferred from XPS results
Phase separation methodology for physicochemical studies of soils.
No full textA detailed study of a soil in every country is of a paramount importance, because it determines an entire economic strategy. The mineralogical properties of soils have been studied in the world for more than 100 years by various characterization techniques, X-ray diffraction being the most prominent. The main difficulty in most of employed techniques is the dominance of the majority phases in the response or the measured signal from the sample that becloud minority phases preventing their identification. The application of methods of phases'separation would provide the possibility to discern minority phases in soils. This work presents a phase separation method that employs a combination of two phenomena based on principles of fluid dynamics: flotation and sedimentation. Different characterization methods were used to analyse the produced soil samples. The methodology employed for separation of phases allowed the complete separation of clay phase from heavier mineral phases. This result makes it possible to discern minority mineral phases of soils that are difficult to detect. A more accurate determination of the mineralogical composition of a soil becomes feasible
Amorphous nitrogenated carbon films: Structural modifications induced by thermal annealing
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