Browsing by Author "Wyndham, E."

Now showing 1 - 13 of 13
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    An analytical model of multi-component radio frequency capacitively coupled plasma and experimental validation
    (2017) Veloso Espinosa, Felipe Eduardo; Wyndham, E.; Favre Domínguez, Mario; Bhuyan, Heman; Saikia, P.
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    Collision dynamics of laser produced carbon plasma plumes
    (2016) Favre Domínguez, Mario; Ruiz, H. M.; Cortés, D.; Merello, F.; Bhuyan, Heman; Veloso Espinosa, Felipe Eduardo; Wyndham, E.
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    Comparative study on the dynamics and the composition between a pulsed laser deposition (PLD) and a plasma enhanced PLD (PE-PLD)
    (2021) Escalona, M.; Bhuyan, H.; Valenzuela, J.C.; Ibacache, S.; Wyndham, E.; Favre, M.; Veloso Espinosa, Felipe; Ruiz, H.M.; Wagenaars, E.
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    Dynamics of laser produced annular plasmas
    (2018) Valenzuela-Villaseca, V.; Veloso Espinosa, Felipe; Munoz-Cordovez, G.; Favre, M.; Ruiz, H.M.; Wyndham, E.
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    Effect of hydrogen addition on the deposition of titanium nitride thin films in nitrogen added argon magnetron plasma
    (2016) Saikia, P.; Bhuyan, Heman; Díaz Droguett, Donovan Enrique; Guzman, F.; Mändl, S.; Saikia, B. K.; Favre Domínguez, Mario; Maze Ríos, Jerónimo; Wyndham, E.
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    Effect of RF acetylene plasma on the composition and dynamics of a titanium plasma plume in a plasma enhanced pulsed laser deposition system
    (2025) Bhuyan, H.; Escalona, M.; Villegas, R.; Mal, E.; Cisternas, M.; Saikia, P.; Bora, B.; Kausik, S. S.; Wyndham, E.; Favre, M.
    We report the effect of radio frequency (RF) acetylene plasma on the dynamics and composition of titanium (Ti) plasma plume in a plasma-enhanced pulsed laser deposition (PEPLD) system. The titanium target, mounted inside a capacitively coupled RF discharge, was ablated by using a nanosecond Nd:YAG pulsed laser at 1064 nm with a power density of 2.65 GW/cm(2). The experiments were performed at different operating pressures of acetylene. Fast imaging and optical emission spectroscopy were employed to study the physics behind the pulsed laser deposition in both (PLD) and PEPLD systems. A nonlinear dependence of the plasma plume evolution was observed over a range of pressure. Different expansion regimes correspond to the pressure of the experiments. The plume expansion velocity ranges between 6 x 10(3) m/s and 30 x 10(3) m/s. Emission spectra reveal the presence of C II and Ti II lines depending on the experimental conditions. The presence of background RF plasma leads to substantial enhancement of the emission intensity of the C II spectral lines. In addition, with increasing RF power and background pressure, the intensities of the C II spectral lines increase; whereas the intensities of the Ti II spectral lines decrease with the increase in RF power. Plasma temperature was estimated from the Ti II lines using the Boltzmann plot method, whereas the electron density was estimated from the Stark-broadened Ti II line at 454.9 nm. The calculated densities and temperatures lie between 10(17)-10(18 )cm(-3) and 0.8-2.0 eV, respectively. These results show the effects of the different backgrounds (either neutral or RF plasma) on the propagation of the laser-produced plasma (LPP), which we propose to be useful in the thin film deposition process using PLD.
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    Experimental studies of ion beam anisotropy in a low energy plasma focus operating with methane
    (2006) Bhuyan, H.; Favre, M.; Valderrama, E.; Chuaqui, H.; Wyndham, E.
    We have investigated, with time and space resolution, the ion beam emission from a plasma focus (PF) device, operating in methane, at 20 kV, with 1.8 kJ stored energy. A detector array is used to measure simultaneously the ion beams at five different angular directions with respect to the PF axis (0 degrees, 10 degrees, 15 degrees, 20 degrees and 90 degrees), at a distance of 77 cm from the ion source. Ion beam energy correlations for operation in methane indicate that the dominant charge states on the detector are H+, C+4 and C+5, irrespective of the angular positions. The time integrated ion beam signal and the energy-dispersive x-ray analysis of a carbon films deposited on silicon surface shows the impurity emission from the PF electrode surface. Measured ion fluxes are maximum for the energy range of 15-40 keV, 50-100 keV and 100-300 keV, for H+, C+4, and C+5, respectively. Measurements of the angular distribution of hydrogen and carbon ions reveal a strong angular anisotropy. It is argued that the observed angular anisotropy of the ion beam emission can be explained in terms of ion Larmor radius effects during the z-pinch like plasma formation phase, which is characteristic of PF discharges.
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    Formation of hexagonal silicon carbide by high energy ion beam irradiation on Si(100) substrate
    (2007) Bhuyan, H.; Favre, M.; Valderrama, E.; Avaria, G.; Chuaqui, H.; Mitchell, I.; Wyndham, E.; Saavedra, R.; Paulraj, M.
    We report the investigation of high energy ion beam irradiation on Si (100) substrates at room temperature using a low energy plasma focus (PF) device operating in methane gas. The unexposed and ion exposed substrates were characterized by x-ray diffraction, scanning electron microscopy (SEM), photothermal beam deflection, energy-dispersive x-ray analysis and atomic force microscopy (AFM) and the results are reported. The interaction of the pulsed PF ion beams, with characteristic energy in the 60-450 keV range, with the Si surface, results in the formation of a surface layer of hexagonal silicon carbide. The SEM and AFM analyses indicate clear step bunching on the silicon carbide surface with an average step height of 50 nm and a terrace width of 800 nm.
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    Laser-produced annular plasmas
    (AMER INST PHYSICS, 2006) Veloso, F.; Chuaqui, H.; Aliaga Rossel, R.; Favre, M.; Mitchell, I. H.; Wyndham, E.
    A new technique is presented for the formation of annular plasmas on a metal surface with a high-power laser using a combination of axicon and converging lenses. The annular plasma formed on a titanium target in a chamber of hydrogen gas was investigated using schlieren imaging and Mach Zehnder interferometry. Expansion of the plasma was shown to be anisotropic with velocities of similar to 10(3)-10(4) m/s. Electron densities of 10(18) cm(-3) were measured with radial profiles that confirm the presence of a hollow structure. The interferometric observations also show the presence of an inward shock wave traveling to the center of the annular plasma, which compresses the background neutrals, reaching a density around 18 times initial gas density, at 95 ns after the initial annular plasma is produced.
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    NITRIDING OF SUPER-FERRITIC STAINLESS STEEL BY PLASMA IMMERSION ION IMPLANTATION IN RADIO FREQUENCY AND ECR-MICROWAVE PLASMA SYSTEM
    (IEEE, 2015) Bhuyan, H.; Favre, Mario; Cisternas, M.; Henriquez, A.; Wyndham, E.; Mandl, S.; Manova, D.; Walczak, M.
    Stainless steel 470 Li-24 Cr and 460Li-21 Cr are two new generation super-ferritic nickel free grades, contains titanium (Ti), niobium (Nb) and very small percentage of carbon (C) and nitrogen (N). The Ti and Nb enhance the corrosion resistance while the low interstitial content of C and N leads to finer precipitates and greater ductility. These grades are economic alternative to 316L and 304 with corrosion resistance comparable or superior. However, as 316L and 304 can be nitrided efficiently to improve the mechanical surface properties like hardness and wear; it has to be asked whether these new generation super-ferritic grade stainless steels can be improved further by plasma nitriding too. Two sets of experiments have been carried out, one with capacitively coupled radio frequency Plasma at PUC Chile and the other is microwave plasma at IOM Leipzig, to investigate further improvements in the mechanical properties of 470 Li-24 Cr and 460Li-21 Cr steel. Nitrided and unnitrided substrates are further investigated using different surface characterization techniques including secondary ion mass spectroscopy, scanning electron microscopy, energy dispersive x-ray analysis, Vickers hardness, wear resistance, corrosion test etc. In most of the characterizations the nitrided 470 Li-24 Cr and 460Li-21 Cr shows similar results. Increase of surface roughness for higher treatment temperature is observed in both the experiments, independent of the steel types. The formation of chromium nitride compound takes place at treatment temperature around 400 o C-450 o C, and it increases with further increase in temperature. But at higher temperature corrosion property deteriorate. The characterization results show up to 25% of nitrogen, 4-5 times increased in hardness and diffusion of nitrogen layer up to 4-6 micron for different experimental conditions. The samples implanted with temperature higher than 400°C presented wear resistance values around two orders of magnitude higher than the others.
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    Observations of Ablation Dynamics in Wire-Array Z-Pinch Experiments on the Llampudken Generator
    (2012) Veloso Espinosa, Felipe; Suzuki-Vidal, F.; Molina, F.; Mitchell, I. H.; Chuaqui, H.; Favre, M.; Wyndham, E.
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    Radiographic imaging of insects using a copper x-pinch plasma backlighting source
    (2018) Vescovi, M.; Veloso Espinosa, Felipe; Munoz-Cordovez, G.; Valenzuela-Villaseca, V.; Favre, M.; Wyndham, E.
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    Refractive optical measurements on the Llampüdkeñ generator
    (2006) Suzuki, F.; Veloso Espinosa, Felipe; Molina, F.; Mitchell, I.; Chuaqui, H.; Aliaga-Rossel, R.; Favre, M.; Wyndham, E.