A MORPHOLOGICAL GROWTH-MODEL FOR LASER-ABLATED Y1BA2CU3O7-X THIN-FILMS

The aim of this work to investigate the growth mechanism of thin Y1Ba2Cu3O7-x filmS ablated by LPVD. The Y1Ba2Cu3O7-x films were prepared by KrF-excimer laser ablation (248 nm) on SrTiO3 (100) substrates. To investigate film properties like surface morphology, epitaxy, c-axis length, critical current density j(c) (77 K) and critical temperature T(c)off we varied the ablation parameters: target substrate distance d(T-S), oxygen partial pressure p(O2), substrate temperature T(s) and laser energy density I. To analyze the films X-my diffraction, Rutherford backscattering spectroscopy, scanning electron microscopy and electrical measurements were used. Three morphological images (zones) of the Y1Ba2CU3O7-x film growth in dependence on p(O2) and T(s) can be distinguished and the growth model of Thornton can be applied as a general rule for optimization of Y1Ba2Cu3O7-x thin film growth. In a medium zone (zone T in the Thornton model) of p(O2) almost-equal-to 70 Pa and T(s) almost-equal-to 720-degrees-C with d(T-S) = 4 cm and 1 = 4.3 J/cm2 we get smooth, epitaxial films with T(c)off > 90 K and j(c) (77 K) > 3 x 10(6) A/cm2. At high p(O2), high (d(T-S) and low I we found outgrowths on the films which are of the same stoichiometry as the surrounding film material.