Aluminum nitride (AlN) films were grown on sapphire substrates by radio frequency magnetron sputtering in plasma containing a mixture of argon and nitrogen, using a pure aluminum target. Surface morphology dependence of the AlN films on growth conditions such as substrate temperature and nitrogen concentration was investigated. c-axis preferred wurtzite AN film with surface roughness as small as 2.9 nm was obtained at substrate temperature of 100 degrees C and nitrogen concentration of 20%. The surface roughness of the AlN films increased with increasing substrate temperature and nitrogen concentration. The correlation between the growth conditions and the film morphology was discussed. (c) 2004 Elsevier B.V. All rights reserved.