Aligned hexagonal coaxial-shaped ZnO nanocolumns on steel alloy by thermal evaporation

Single-crystalline, hexagonal coaxial-shaped ZnO nanocolumns have been synthesized in a large quantity on steel alloy substrate via catalyst-free thermal evaporation of metallic zinc powder at 490°C. The optical-phonon E2 mode at 437cm−1 in Raman spectrum and a strong UV emission at 381nm in photoluminescence spectrum showed that the synthesized ZnO nanocolumns have a good crystal quality, with a wurtzite hexagonal phase and exhibited a good optical property. A layer-by-layer three-step growth mechanism was proposed for the formation of hexagonal coaxial-shaped ZnO nanocolumns.