Organic light emitting devices (OLEDs) using Alq(3) have been fabricated by employing two techniques: energetic cluster evaporation and normal thermal evaporation. Atomic force microscopy taken on the Alq3 film surfaces obtained from both techniques revealed that using energetic clusters was advantageous over normal thermal evaporation in terms of surface roughness particularly when the film grows thicker than 50 nm. OLEDs with the critical thickness of 50 nm, prepared by energetic cluster evaporation, thus showed much better performances in both current-voltage (I-V) and luminance-voltage (L-V) curves than devices prepared by thermal evaporation. The lifetime of the energetic-cluster-prepared OLED was also found to be longer than those of devices prepared by thermal evaporation. (C) 2004 American Vacuum Society.