Thin SolidFilms, 191 (1990)317 334 PREPARATIONAND CHARACTERIZATION 317 FORMATION OF Y-Ba-Cu-OXIDE THIN FILMS BY PULSED LASER DEPOSITION: A COMPARATIVE STUDY IN THE UV, VISIBLE AND IR RANGE WOLFGANG KAUTEK Laboratory for Chemical Surface Technologies, Federal Institute for Materials Research and Testing (BAM), Unter den Eichen 87, D-IO00 Berlin 45 (F.R.G.) BERNHARD ROASAND LUDWIG SCHULTZ Siemens AG. Research Laboratories, Paul-Gossen-Strasse 100, D-8520 Erlangen (F.R.G.) (Received January 20, 1990;revised April 10, 1990;acceptedApril 27, 1990) A study of the correlation between the pulsed laser deposition process and the specific interaction of the laser light with the target material in a wide wavelength range between far-UV and near-IR was performed. Sintered Y-Ba-Cu-oxide targets were irradiated with laser pulses of the order of 108-109Wcm -2 to generate an energetic material beam which was collected on zirconia substrates placed nearby. Visible and IR light penetrates deeply into the targets and is converted mainly into heat. This results in abrupt evaporation, rough remnant surface features on the target and splashing on the substrate film. Less than (0.3-0.5 × 109) W cm - 2 of UV light leads to incongruent evaporation with, typically, yttrium deficiency on the substrate. Above this power threshold, favourably stoichiometric and smooth films are generated by UV laser light. The observed phenomena are explained in terms of competing energy dissipation mechanisms on the target surface. 1. INTRODUCTION A technique for synthesizing high. quality thin films of high temperature superconductors must be able (a) to produce smooth films with (b) sharp interfaces and (c) the appropriate elemental composition and (d) to obtain the right crystal phase. Thin YBa2Cu3OT_x films have been produced by electron beam co- deposition l'2, molecular beam epitaxy 3, sputtering 4-7, thermal evaporation s'9, chemical vapour deposition 1°'~1, and pulsed laser deposition (PLD) ~2-21. An amorphous film is deposited and either post-annealed up to 900 °C ex situ (see, for example, refs 13-15 and 17) or, more recently, annealed in situ in the laser process chamber (see, for example, refs. 16, 18 and 21). In the case of ejection of the elements from separate sources using heat, electrons, or ions, the relative ejection rates of the elements and the non-overlap of the atomic trajectories from the three sources (yttrium, barium, copper) form a serious technical problem. However, the use of single targets has its own problems: the ejection rates or the sputtering yields of the 0040-6090/90/$3.50 © ElsevierSequoia/Printed in The Netherlands