Elaboration of alumina nanowire field normal to a generic substrate

Nanoporous alumina film was realised on a silicon substrate. The structure investigated by scanning electron microscopy is presented and reveals homogeneous pores on the entire sample surface. The pore-cell is polygonal and has sometimes a hexagonal shape. The pore-cell is limited by six-edges, leading to alumina nanowires brushes normal to the substrate after an enlargement of the pores. Owing to the geometry of the initial pore structure, the resulting nanowires have an exponential shape with a foot larger than the top, leading to good mechanical behaviour. The alumina annealing has also been investigated by grazing incidence X-ray diffraction measurements and reveals the presence of the γ-Al₂O₃ phase for a temperature upper than 800°C.