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search.filters.applied.f.access: openAccess × Author: Lorenz, Pierre × End date: 2019 × Start date: 2010 × Publisher: Amsterdam [u.a.] : Elsevier × Subject: Konferenzschrift ×

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Now showing 1 - 4 of 4
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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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    Nanostructuring of Fused Silica Assisted by Laser-shaped Metal Triangles Using a Nanosecond Laser
    (Amsterdam [u.a.] : Elsevier, 2016) Lorenz, Pierre; Grüner, Christoph; Ehrhardt, Martin; Bayer, Lukas; Zimmer, Klaus
    Self-organized processes are of special interest for the laser-induced nanostructuring of surfaces. In this study we combined two self-organized processes: the microsphere lithography and the molten phase transformation for the nanostructuring of dielectrics. A fused silica substrate was covered with periodically ordered polystyrene (PS) spheres and the system was subsequently covered with 30 nm chromium. Afterwards the PS spheres were removed and the bare and resultant periodic Cr triangles were irradiated in two steps using a KrF excimer laser. First step: A low laser fluence treatment results in a melting and shape transformation of the triangles. Second step: A high laser fluence treatment of the pre-treated surface results in a nanostructuring of the dielectric surface (and removal of the metal). The surface topography was studied by scanning electron microscopy. Furthermore, the different steps were simulated and compared with the experimental results.
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    Shock-wave-induced Thin-film Delamination (SWIFD): A Non-thermal Structuring Method of Functional Layers
    (Amsterdam [u.a.] : Elsevier, 2016) Lorenz, Pierre; Ehrhardt, Martin; Bayer, Lukas; Zimmer, Klaus
    The laser structuring of thermally sensitive functional layers is a challenge for laser methods. However, already ultrashort laser pulses can induce thermal modifications. The spatial separation of the laser pulse absorption from the functional layer removal process allows a non-thermal structuring process. Therefore, the rear side of the substrate is irradiated and the following laser ablation process induces a transverse shock wave through the substrate. Finally, the interaction of the shock wave with the substrate/functional layer interface results in a delamination of the functional layer. This shock-wave-induced thin-film delamination (SWIFD) method was tested on a layer system (1.5 μm thick epoxy-based negative photoresist SU 8, 250 nm–1 μm chromium layer) on a 25 μm polyimide flexible substrate where the influence of the systematic variation of the thickness of the metallic intermediate layer on the delamination process was studied. The resultant surface morphology was analyzed by optical microscopy as well as by white light interferometry (WLI).
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    From statistic to deterministic nanostructures in fused silica induced by nanosecond laser radiation
    (Amsterdam [u.a.] : Elsevier, 2018) Lorenz, Pierre; Klöppel, Michael; Zagoranskiy, Igor; Zimmer, Klaus
    The production of structures by laser machining below the diffraction limit is still a challenge. However, self-organization processes can be useful. The laser-induced self-organized modification of the shape of photolithographic produced chromium structures on fused silica as well as the structuring of the fused silica surface by nanosecond UV laser radiation was studied, respectively. Low fluence single pulse laser irradiation (□ > 300 mJ/cm2) cause the formation from chromium squares to droplets due to the mass transport in the molten chromium film. This process is governed by the instability of the molten metal due to the surface tension driven liquid phase mass transport. For a chromium pattern size similar to the instability length two specific droplet distributions were found which are single droplets with a determined position near the centre of the original pattern or random distributed smaller droplets arranged circularly. Each of the metal patterns can be transferred into the fused silica by a multi-pulse irradiation. The experimental results can be simulated well for low fluences by sequential solving the heat and Navier-Stokes equation.