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 (000(-)1) 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 (000(-)1)-O with +/- (01(-)10) surfaces.