Periodic arrays of Ta nanopillars were grown onto patterned substrates by glancing angle sputter deposition at growth temperatures T-s ranging from 200 to 900 degrees C. The Si substrates were patterned using a colloidal suspension of 260-nm-diameter silica spheres that was dispersed to form a two-dimensional close-packed monolayer. At low growth temperatures, T-s <= 500 degrees C, nanopillars exhibit regular hexagonal arrays. However, the arrays randomize with increasing T-s and completely degrade at T-s = 900 degrees C. The transition to a less Ordered film morphology is attributed to strong interpillar competition caused by the increasing adatom diffusion length with increasing T-s. The competitive growth mode leads to a decrease in the pillar number density (by 48%) and pillar separation (from 65 nm to negligible), an increase in the average pillar width from 200 to 260 nm, the accelerated growth of some pillars at the cost of others which die out (25%), and an increased probability (20%) for the merging of neighboring pillars. (c) 2007 American Vacuum Society.