Browsing by Author "Valderrama, E."

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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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    Spectroscopic characterization of RF hydrocarbon plasmas for DLC coatings
    (2014) Guzmán, F.; Ruiz, M.; Valderrama, E.; Favre Domínguez, Mario; Bhuyan, Heman; Wyndham, Edmund; Chuaqui, Hernán