Laser-induced forward transfer: A new approach for the deposition of high T c superconducting thin films
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Groupe de Physique des Solides de VENS, Universite Paris VII, 2 Place Jussieu, F-75251 Paris Cedex 05, France (Received 8 December 1988; accepted 17 April 1989) We propose in this work a new approach, named laser-induced forward transfer, for the rapid deposition and patterning in a clean environment of high Tc superconducting thin films. A stoichiometric high Tc compound is initially deposited in a thin layer on an optically transparent support by laser evaporation or another more conventional technique. By irradiating under vacuum or in air the precoated layer with a strongly absorbed single laser pulse through the transparent support, we are able to remove the film from its support to be transferred onto a selected target substrate, held in contact to the original film. Using this technique, we have successfully transferred with one single pulse, provided by an excimer or a Nd:YAG laser, YBaCuO and BiSrCaCuO precoated thin films on various substrates. The Rutherford backscattering spectrometry experiments do not show any strong modification in the composition of the transferred layer against the source material, and the superconducting phases for the two types of compounds were obtained after subsequent thermal annealing carried out in a furnace around 850-900 °C in O2. For the BiSrCaCuO films transferred onto MgO substrates, we have measured an onset critical temperature of about 90 K with a zero resistance at 80 K. I. INTRODUCTION Laser-assisted techniques for thin film deposition of a wide variety of materials 1 ' 2 including recently the new high Tc YBaCuO 3 ' 4 and BiSrCaCuO5"7 superconductor compounds have been the subject of extensive research these last years, mainly for micro- and opto-electronic applications. In this field, we propose a new approach for depositing high Tc superconductor thin films using the laser-induced forward transfer (LIFT) technique,8'9 which appears to be especially suitable for the patterning10'n of high Tc films. With the LIFT technique, a thin film of material to be deposited is initially precoated on an optically transparent support. This precoated support is then placed near or in contact with a selected target substrate. By irradiating the precoated film under vacuum or in controlled atmosphere (air, O2) with a strongly absorbed single laser pulse through the transparent support, the film can be removed from the support to be transferred onto the selected substrate without involving any kind of chemical processes. In addition, the output of the pulsed laser used in this technique can be patterned either by passing through a mask (mask patterning) or by focusing the beam with a lens system (direct patterning). So it is anticipated that in optimizing conditions, a spatial resolution approaching that of laser-assisted depositions from gas-phase precursors can be achieved.1'2 In this work, we demonstrate for the first time that YBaCuO and BiSrCaCuO precoated thin films of about 1082
http://journals.cambridge.org
J. Mater. Res., Vol. 4, No. 5, Sep/Oct 1989
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