Volume and size distribution of droplets in oxide films were investigated for a variety of laser fluences, wavelengths and target temperatures. Effects of both the ambient gas pressure and the substrate temperature on the droplet formation was investigated. It was found that the increase in the ratio of the droplet volume to the film volume Vd /Vf caused by increasing the maximum etching depth of target per laser shot de (Vd /Vf ∝ de 3 ,as previously reported) due to changes in the deposition conditions other than the target temperature is mainly attributed to an increase in the formation of large droplets. It was also found that the correlation Vd /Vf ∝ de 3 is valid also for elevated target-temperatures, and the increase in the target temperature enhances the formation of small droplets compared with large ones. The effect of cooling of droplets after the ejection from the target due to the ambient pressure and/or the substrate temperature is discussed.

The effect of ambient gas on the preparation of YBa 2 Cu 3 O x (YBCO) high-T c superconducting thin films by pulsed laser ablation was explored in gas mixtures of argon + oxygen, argon + nitrous oxide, and nitrous oxide + oxygen. These experiments revealed that a reducing environment for the preparation of YBCO films enhances the film growth with the high temperature phase (trilayered perovskite YBCO) rather than the low temperature phase (cubic YBCO). This phenomenon is explained in terms of thermodynamic phase diagram. The effect of nitrous oxide on the thermodynamic phase diagram is far smaller than that of oxygen by a factor of two to three orders of magnitude.