Nanostructured films of AIN, GaN, and InN were grown via a reactive magnetron sputtering technique without templates or catalyst. The growth of nanorod arrays or two-dimensional compact films can be switched by fine tuning nitrogen content in sputtering gas. The nanorods grow along [001] direction with a diameter of similar to 100-500 nm. AIN has a cone shape with an apical tip radius of similar to 2 nm. A growth mechanism involving in the mobilities of metallic adatoms (such as Ga, Al, and In) and N adatoms on different crystallographic planes is presented for formation of nanorod arrays. (c) 2007 Elsevier B.V. All rights reserved.