Regular arrays of Ta nanopillars, 200 nm wide and 500 nm tall, were grown on SiO2 nanosphere patterns by glancing angle sputter deposition (GLAD). Plan-view and cross-sectional scanning electron microscopy analyses show dramatic changes in the structure and morphology of individual nanopillars as a function of growth temperature T, ranging from 200 to 700 degrees C. At low temperatures, T-s <= 300 degrees C, single nanopillars develop on each sphere and branch into subpillars near the pillar top. In contrast, T-s >= 500 degrees C leads to branching during the nucleation stage at the pillar bottom. The top branching at low Ts is associated with surface mounds on a growing pillar that, due to atomic shadowing, develop into separated subpillars. At high Ts, the branching occurs during the nucleation stage where multiple nuclei on a single SiO2 sphere develop into subpillars during a competitive growth mode which, in turn, leads to intercolumnar competition and the extinction of some nanopillars. (c) 2006 Elsevier B.V. All rights reserved.