The effects of variations in laser fluence and pulse repetition rate on YBCO thin films.

Epitaxial thin films of YBCO were grown to a thickness of similar to 200nm by pulsed laser deposition onto single crystal (001) MgO substrates with systematic variations in the laser fluence and pulse repetition rate. RBS ion beam channeling spectra proved the films to be of good crystallinity with minimum channeling yields for Barium (chi(min,Ba)) between 4 and 12%. Comparison of the channeling minima obtained from the magnesium signals by RBS angular scans indicated the misorientation between film and substrates to vary between 0 and 0.6 degrees. The deposition rate per pulse was found to be independent of the repetition rate but appears to vary with the square of the laser fluence. The density of growth spirals was found to increase with both repetition rate and laser fluence.