Probing timescales during back side ablation of Molybdenum thin films with optical and electrical measurement techniques.
In this study we present a new measurement technique to investigate the timescales of back side ablation of conductive films, using Molybdenum as an application example from photovoltaics. With ultrashort laser pulses at fluences below 0.6 J/cm(2), we ablate the Mo film in the shape of a fully intact Mo 'disc' from a transparent substrate. By monitoring the time-dependent current flow across a specifically developed test structure, we determine the time required for the lift-off of the disc. This value decreases with increasing laser fluence down to a minimum of 21 ± 2 ns. Furthermore, we record trajectories of the discs using a shadowgraphic setup. Ablated discs escape with a maximum velocity of 150 ± 5 m/s whereas droplets of Mo forming at the center of the disc can reach velocities up to 710 ± 11 m/s.
Robert Bosch GmbH, CR/APJ2, PO Box 300240, 70442 Stuttgart, Germany.
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Bartl
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Ametowobla
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Schmid
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Letsch
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Hafner
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Nolte
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Tünnermann
D003217:Conductometry / Q000379:methods*; D007834:Lasers; D008422:Materials Testing / Q000379:methods*; D008567:Membranes, Artificial; D008982:Molybdenum / Q000032:analysis / Q000737:chemistry* / Q000528:radiation effects*; D012031:Refractometry / Q000379:methods*
D008567:Membranes, Artificial; D008982:Molybdenum