Near-surface chemical diffusion at room temperature, in thin films with their a-axis orientation normal to the substrate, was studied by using 4-probe direct-current conductivity measurements. The results showed that, under given experimental conditions, the O out-diffusion coefficient was some 2 orders of magnitude higher in the present films, than in those with their c-axis normal to the substrate. The out-diffusion was also enhanced by ultra-violet light.

B.Pashmakov, K.Zhang, H.M.Jaeger, P.Tiwari, X.D.Wu: Physica C, 1995, 249[3-4], 289-92