We report a study of the annealing temperature and time on Ag catalyst size and density for subsequent growth of ZnO nanorods by catalyst-driven molecular beam epitaxy (MBE). Two different substrates (SiO2 and SiNX) for the Ag deposition were used and the thickness of the Ag held constant at 25 angstrom. Annealing between 600 and 800 degrees C produced Ag cluster sizes in the range 8-30 nm diameter on SiO2 and 10-65 nm on SiNX with a cluster density from 100 to 2500 mm(-2) for SiO2 and 30 to 1900 mm(-2) for SiNX. ZnO nanorods grown on these clusters show single-crystal, wurtzite-phase nature and strong band-edge photoluminescence at 380 nm. The nanorods can also be grown selectively on lithographically-patterned dielectric stripes with Ag clusters formed on top by e-beam evaporation and annealing. (c) 2006 Elsevier B.V. All rights reserved.