The effects of annealing ambient on the He-induced voids in silicon were investigated using the combination of the Doppler broadening spectroscopy using a variable-energy positron beam and cross-section transmission electron microscopy (XTEM). A < 1 0 0 >-oriented silicon wafer was implanted with He ions at an energy of 15 keV to a dose of 2 x 10(16) cm(-2) at room temperature. Post-implantation, the samples were annealed at a temperature of 1000 degrees C in the ambient of vacuum, argon, nitrogen, air and oxygen. Positron annihilation spectroscopy (PAS) spectra varied with the annealing ambient. XTEM micrographs demonstrated that the density of He-induced voids could be influenced by the annealing ambient. (C) 2011 Elsevier B.V. All rights reserved.