Enhanced anomalous diffusion of sputtered atoms in nanosized pores

Plasma sputtering deposition of platinum catalysts in porous anodic aluminum oxide (AAO) templates is shown to generate an anomalous superdiffusion concentration profile. The growth of an overlayer between the hexagonal array of pores is shown to enhance the diffusion into the pores, leading to a diffusion coefficient having superlinear time dependence. The Pt clusters in the pores have a mean size of 10 nm and almost concentrate on the inner pore surface, and are present up to a depth of 6 μm.