OPTIMIZATION OF DEPOSITING Y1BA2CU3O7-DELTA SUPERCONDUCTING THIN-FILMS BY EXCIMER LASER ABLATION WITH CO2 LASER-HEATED SUBSTRATES

Abstract

The optimum deposition conditions for growing Y1Ba2Cu3O7-delta superconducting thin films in situ by using xenon, Nd:YAG, and KrF excimer lasers with CO2 laser-heated substrates were studied. The dependences of the T(c0) and microstructure of the films on the deposition parameters such as substrate temperature, oxygen partial pressure, laser energy density and repetition rates have been investigated systematically. It was found that both the surface mobility on the substrate and the reaction temperatures for the particulates arriving at the substrates are the key factors for obtaining high-quality films. High-quality Y1Ba2Cu3O7-delta thin films with mirror-like surface morphology, T(c0) almost-equal-to 90 K, and nearly perfect c-axis oriented normal to the film surface were routinely grown in situ on SrTiO3 substrates with the following deposition conditions: substrate temperature at 670-degrees-C, oxygen partial pressure of 0.1 torr, laser energy density of 4 J/cm2 per pulse, and repetition rate of 10 Hz. More significantly, it took only about 3 min to grow a 0.3-mu-m thick film and less than 50 s to cool down the film to room temperature after deposition by the present process. Subsequent processes, such as slow cooling in oxygen atmosphere or any further heat treatments, were unnecessary for the present process. The unique advantage of the present process further offered us good opportunities to delineate the effects of each deposition parameter on the detailed film growth mechanisms without having to deal with the complications introduced by prolonged post-deposition treatments. The details of all the interesting features observed will be presented and their physical implications will be discussed.