The diffusion of O through the grain boundaries of Pt films during annealing was investigated. When the Pt film was sputtered onto a TiN film  in vacuo, columnar (111)-oriented grains grew with continuous grain boundaries normal to the substrate. On the other hand, a Pt film which was deposited onto a TiN film that had been exposed to air, consisted of granular grains with a random orientation. This was because the Pt film grew on the native oxide of the TiN. The degree of O diffusion in Pt film which was deposited onto exposed TiN films was lower than that in non-exposed TiN film during annealing at 650C in O2. It was concluded that differences in the grain-boundary structure, such as the diffusion length, determined the O diffusion rate.

Oxygen Diffusion in Pt Bottom Electrodes of Ferroelectric Capacitors Y.Matsui, M.Suga, M.Hiratani, H.Miki, Y.Fujisaki: Japanese Journal of Applied Physics - 2, 1997, 36[9A/B], L1239-41