Influence of porosity on the critical currents of trifluoroacetate-MOD YBa/sub 2/Cu/sub 3/O/sub 7/ films

The influence of porosity on the superconducting properties have been investigated on YBa/sub 2/Cu/sub 3/O/sub 7/ thin films deposited on LaAlO/sub 3/ [100] substrates by the so-called Trifluoroacetate (TFA) route. Micro-Raman spectroscopy have been used to determine the concentration of c-axis grains (delta) in different samples and their influence on the final film porosity as observed from SEM imaging. This has been compared with measurements of resistivity and critical currents in the same samples. We prove that this (delta) fraction is the main parameter controlling the porosity and hence the normalstate resistivity of the thin films. The optimization of the microstructure of these YBa/sub 2/Cu/sub 3/O/sub 7/ TFA films allow to have high critical currents : J/sub c/ = 3 * 10/sup 6/ A/cm/sup 2/ at 77 K.