AlN nanocrystalline layers and superstructures are used in the modern optoelectronic technology as reflecting mirrors in semiconductor lasers. In the present work the properties of AlN films prepared by sputtering methods from an AlN target in reactive Ar + N plasma were investigated. The characterisation was performed with HRTEM, SEM, glancing angle XRD and RBS methods. The present measurements confirmed the polycrystalline structure of AlN layers and enabled the evaluation of their grain size. The roughness and thickness of the layers were additionally determined by ellipsometric and profilometric measurements.
Enrichment of AISI 316L steel surface layers with rare earth elements was carried out using two methods with ion beam applying. The first one was the ion implantation with the doses in the range of 1 × 10^{15} cm^{-2} up to 5 × 10^{17} cm^{-2} where mishmetal (Ce+La) was used as the ion source. The second method was the high intensity pulsed plasma beams. The plasma pulses contained both ions/atoms of Ce+La from the electrodes material (mishmetal). The pulse energy densities (3 J/cm^2) were sufficient to melt the near surface layer of the steel and introduce those elements into the surface layer. The aim of this work was to investigate the changes of stainless steel surface properties (morphology, rare earth elements concentration, presence of identified phases) after the rare earth elements addition with or without melting. Scanning electron microscopy, energy dispersion spectroscopy, and X-ray diffraction analysis were used for initial and modified surface characterisation. Grazing-incidence X-ray diffraction shows differences in the identified phase presence in the modified surface layer connected with the modification method.
Diamond-like carbon (DLC), in particular hydrogenated amorphous carbon (a-C:H) films have been formed on various conductive and dielectric materials by plasma immersion ion implantation and deposition (PI^{3}D) processing. Effect of pulse voltage and other process parameters on the film properties was investigated. It was found that for conductive substrates, a low-voltage ( ≈1 kV), high repetition rate pulsing provides better overall film performance comparing to that obtained by applying higher voltages, which is also favourable for conformal treatment of 3D workpieces. However, short 1-2 μs, high-voltage 5-20 kV pulses are required for dielectric workpieces several millimeter thick. Good film adhesion was achieved by forming a Si-containing buffer layer using hexamethyldisiloxane (HMDSO) as a precursor and a low-voltage pulsing. Roughness and wettability of DLC coatings was found to be controlled by varying the bias specs and sample temperature. Very smooth films with average roughness less than 1 Å were prepared at optimised process parameters.
In the present paper we propose a model of physical phenomena behind the front face of the electrodes in an impulse plasma accelerator. The model is based on the results of recent experimental observations and measurements. It correlates plasma dynamics with mechanism of phenomena in a column of pinching plasma. On the contrary to the previous model the current one suggests the series of relatively short pulses of metallic ions from the erosion of electrode material. Till now the pinch was treated rather as a nearly continuous source of metallic plasma, feeding the process with ions from the erosion of electrode material.
Silicon organic thin films have been prepared by RF hollow cathode plasma chemical vapor deposition system, from hexamethyldisilazane (HMDSN) as the source compound, under different plasma conditions, namely feed gas and applied RF power. The feed gas has been changed from argon to nitrogen, and the power has been varied between 100 W and 300 W in N_2/HMDSN plasma. The structural properties of the deposited films have been investigated by the Fourier transform infrared spectroscopy technique. Spectrophotometry measurements have been used to determine films optical constants (refractive index, dielectric constant and energy band gap); in addition, the photoluminescence from these films has been recorded. The electrical resistivity of films has been estimated from the measurements of current-voltage characteristics of deposited thin films. The effect of the different plasma conditions on these structural, optical and electrical properties of the prepared thin films, as well as the correlation between the different properties are reported.
The annealed low alloy 4140 steel samples have been nitrided for different treatment periods (1-6 h) in an RF inductive plasma discharge with very low bias voltage ( ≈ 400 V). The resulting nitrided layer has been observed by means of an optical microscope whereas the nitride phases have been characterised by X-ray analysis. The corrosion response, assessed by the potentiodynamic tests in the 3.5% NaCl solution, presents both higher noble potential values and lower corrosion rates when compared with the untreated sample. The Vickers microhardness tests values show an appreciable increment compared to that of the untreated sample. The process is characterized by a high overall efficiency because similar average Vickers tests values were obtained, no matter for how long the treatment was extended. Likewise, the scanning electron micrographs confirmed no appreciable size evolution of the compound layer microstructure at different times of treatment.
With incident fluences of ≈ 10^{12} atoms/cm^2 aluminium samples have been plasma immersion ion implanted with either pure nitrogen or argon/nitrogen mixtures at temperatures around 450°C. X-ray diffraction studies have validated the formation of the cubic phase of AlN, in samples treated with both the gas mixtures and pure nitrogen. Likewise, the presence of the hexagonal phase of AlN has been detected when either pure nitrogen or a 70%N/30%Ar mixture have been used. The signature peak of AlN has also been confirmed by the Raman spectroscopy. The maximal microhardness values were found in samples treated with the mixture. The maximal roughness was achieved with the equal part mixture in all cases, although increasing with the implantation pulse width up to a 300 nm peak at 150 μs. The latter critical value remains invariant under the pure nitrogen plasma treatment, provided that implantation periods in the order of 4.5 h are carried out.
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