Nanowires of gallium oxynitride with wurtzite type structure were grown using seed crystals obtained by ammonia nitridation of an amorphous gallium oxide precursor containing 3 at% nickel additive. The seed crystals on a silica substrate were annealed with the amorphous gallium oxide precursor under ammonia flow to grow gallium oxynitride nanowires. The nanowires grew to lengths of about 150 mu m along the seed crystals parallel to the hexagonal c-plane at 750 and 800 degrees C but they did not grow in the lateral direction. When the growth temperature was increased above 900 degrees C, the growth direction gradually changed to become parallel with the c-axis with a copresenting of gallium-nitride-like crystals. Room-temperature cathodoluminescence spectra of nanowires grown at 800 degrees C exhibited strong blue emission at 2.69 eV along with weak band-edge emission at 3.39 eV, similar to those of GaN. The latter emission was intense for nanowires grown at 1000 degrees C, which had an improved crystallinity and a higher nitride/oxide ion ratio. Nanowires grown at 750 and 900 degrees C exhibited persistent photoconductivity under UV irradiation at 393 nm. (C) 2011 Elsevier B.V. All rights reserved.