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search.filters.applied.f.access: openAccess × Subject: ablation ×

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    Laser Patterning of CIGS thin Films with 1550 nm Nanosecond Laser Pulses
    (Amsterdam [u.a.] : Elsevier, 2016) Ehrhardt, Martin; Lorenz, Pierre; Bayer, Lukas; Zagoranskiy, Igor; Zimmer, Klaus
    The results of laser scribing experiments of CIGS thin films deposited on Mo-coated stainless steel sheets, using laser pulses with a wavelength of 1550 nm and a pulse duration of 6 ns, are presented in this study. It is shown that a removal of the CIGS from the Mo film is possible without edge melting of the CIGS or damaging of the Mo. The critical parameter for inducing the delamination lift-off process of the CIGS from the Mo was identified to be the scribing speed of the laser. In dependence on the laser parameters two different material removal processes were found. For a low pulse overlap the laser pulse penetrates the CIGS film and is absorbed in the interface between the CIGS and the Mo causing a lift-off process of the CIGS from the Mo back contact. For a high pulse overlap an ablation process starting from the top side of the CIGS film was found. The composition and morphology of the sample material after the laser patterning were analysed by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and micro-Raman spectroscopy.
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    Investigation of an Ablation-dominated Arc in a Model Chamber by Optical Emission Spectroscopy
    (Praha : Czech Technical University in Prague, Faculty of Electrical Engineering, Department of Physics, 2017) Methling, R.; Khakpour, A.; Wetzeler, S.; Uhrlandt, D.
    A switching arc in a model chamber is investigated by means of optical emission spectroscopy. Ignition wire is applied to initiate an arc of several kiloampere between tungsten−copper electrodes. Radiation emitted by the arc plasma is absorbed by a surrounding PTFE nozzle, leading to an ablation–dominated discharge. Video spectroscopy is carried out using an imaging spectrometer combined with a high–speed video camera. Carbon ion and fluorine atom line emission from the heating channel as well as copper, oxygen and nitrogen from ignition wire and ambient air are analyzed with focus on the low–current phases at the beginning of discharge and near current zero. Additionally, electrical parameters and total pressure are recorded while the general behavior of the discharge is observed by another video camera. Considering rotational symmetry of the arc the corresponding radial emission coefficients are determined. Finally, radial temperature profiles are calculated.
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    Comparison of surface mass balance of ice sheets simulated by positive-degree-day method and energy balance approach
    (München : European Geopyhsical Union, 2017) Bauer, Eva; Ganopolski, Andrey
    Glacial cycles of the late Quaternary are controlled by the asymmetrically varying mass balance of continental ice sheets in the Northern Hemisphere. Surface mass balance is governed by processes of ablation and accumulation. Here two ablation schemes, the positive-degree-day (PDD) method and the surface energy balance (SEB) approach, are compared in transient simulations of the last glacial cycle with the Earth system model of intermediate complexity CLIMBER-2. The standard version of the CLIMBER-2 model incorporates the SEB approach and simulates ice volume variations in reasonable agreement with paleoclimate reconstructions during the entire last glacial cycle. Using results from the standard CLIMBER-2 model version, we simulated ablation with the PDD method in offline mode by applying different combinations of three empirical parameters of the PDD scheme. We found that none of the parameter combinations allow us to simulate a surface mass balance of the American and European ice sheets that is similar to that obtained with the standard SEB method. The use of constant values for the empirical PDD parameters led either to too much ablation during the first phase of the last glacial cycle or too little ablation during the final phase. We then substituted the standard SEB scheme in CLIMBER-2 with the PDD scheme and performed a suite of fully interactive (online) simulations of the last glacial cycle with different combinations of PDD parameters. The results of these simulations confirmed the results of the offline simulations: no combination of PDD parameters realistically simulates the evolution of the ice sheets during the entire glacial cycle. The use of constant parameter values in the online simulations leads either to a buildup of too much ice volume at the end of glacial cycle or too little ice volume at the beginning. Even when the model correctly simulates global ice volume at the last glacial maximum (21 ka), it is unable to simulate complete deglaciation during the Holocene. According to our simulations, the SEB approach proves superior for simulations of glacial cycles.