Morphology-controllable synthesis of highly ordered nanoporous diamond films

The remarkable functional properties of diamond depend not only on its physical and chemical properties but also on its surface morphology. Ordered porous diamond with hierarchical structures is used in various applications in the fields of environment and energy management. However, obtaining such micro- and nanostructures via conventional techniques has proven to be challenging because of the superhardness and extreme chemical inertness of diamond. In this study, a strategy to create highly textured diamond films structured by vertical columnar crystals was developed. The mechanism of shape-evolution of diamond grains was proposed to account for the changes in the crystal shape from octahedron through cubo-octahedron to cube, followed by oxidation and hydrogenation. Shape evolution of diamond crystals during the initial fabrication stages was assessed by scanning electron microscopy, which revealed that the surfaces of fabricated diamond consisted of rough octahedral {111} and smooth cubic {100} faces. The variation of the crystal shape depended on the relative growth rate of {111} faces to that of {100} faces during the growth process. Finally, highly ordered porous diamond films with switchable wettability properties were obtained by post-fabrication modification involving thermal etching in air followed by etching in hydrogen plasma. (c) 2017 Elsevier Ltd. All rights reserved.