Microstructure of epitaxial superconductive YBa[sub 2]Cu[sub 3]O[sub 7] thin films prepared at different deposition rates.

A study is reported on the growth mechanism of YBa[sub 2]Cu[sub 3]O[sub 7] with different growth speeds by high resolution transmission microscopy (HRTEM) and analysis of the interface and thin film microstructure. Two thin films were synthesized by pulse laser deposition on [100], miscut 5°, SrTiO[sub 3] substrate at 820°C, one with a pulse laser frequency of 1Hz and one with 6Hz. Cross-sections were studied by an H-9000 NAR HRTEM along the [010] direction. The growth process of the sample made at 1Hz was as follows. First, distorted step flow growth occurred on a step-mediated substrate surface of 3–4 cells thickness. Second, about a 15nm thickness of island shape growth becomes superimposed on the area of the step flow layer. Finally, thin film growth occurred but with growth fluctuation. The sample made at 6Hz showed the characteristics of island growth; the growth area of island or ball shape was of small size and dense distribution, and seemed to be a confused mosaic stack. The influence of growth speed on YBCO epitaxial film microstructure was studied explicitly by HRTEM. [ABSTRACT FROM AUTHOR]