Induced Growth of Asymmetric Nanocantilever Arrays on Polar Surfaces

We report that the Zn-terminated ZnO (0001) polar surface is chemically active and the oxygen-terminated (0001) polar surface is inert in the growth of nanocantilever arrays. Longer and wider ``comblike'' nanocantilever arrays are grown from the (0001) -Zn surface, which is suggested to be a self-catalyzed process due to the enrichment of Zn at the growth front. The chemically inactive (0001) -O surface typically does not initiate any growth, but controlling experimental conditions could lead to the growth of shorter and narrower nanocantilevers from the intersections between (0001) -O with (0110) surfaces.