A study was made of O transport in c-axis oriented thin films. Out-diffusion experiments were performed by heating the films in an ultra-high vacuum. A rotating analyzer ellipsometer was used to monitor the process. It was found that the results could not be explained without assuming that short-circuits were present in the films. The O diffused to the short-circuits via the ab-planes. The O then left the film via these short-circuits. The average spacing between the latter was 2500nm. No outward O diffusion occurred along the c-axis.

W.A.M.Aarnink, R.P.J.Ijsselsteijn, J.Gao, A.Van Sifhout, H.Rogalla: Physical Review B, 1992, 45[22], 13002-7