This paper describes the surface morphology, composition, and structure of aluminum nitride (AlN) thin films formed by single ion-beam sputtering of Al. Either pure N2 or a N2 (75%) + H2 (25%) gas mixture was used as the feed gas for the ion gun. The films formed from the hydrogen containing feed gas were deposited on substrates either at room temperature or at 200-degrees-C. The film surface was extremely smooth for films grown under all the deposition conditions : scanning force microscopy indicated less-than-or-equal-to 1 nm average roughness over a 500 x 500 nm2 area. Transmission electron microscopy examination of the films showed that they were highly textured : the c axis of the AlN grains is preferentially oriented perpendicular to the film/substrate interface. The films grown with pure N2 consisted of grains in the order of 100 nm in diameter whereas films formed with a hydrogen containing feed gas had at least an order of magnitude smaller grain size.