We report the fabrication of one dimensional ZnO nanostructures under various argon sputtering pressures by radio frequency magnetron sputter deposition technique. The transition of the nanostructures from vertical to inclined is monotonously increased with the argon sputtering pressure owing to the decrease in migration length of the adatoms by the increased number of collisions. The blue shift, intensity quenching and peak broadening of A(1)(LO) phonon mode in the Raman spectra indicates the increase of free carrier concentration with the argon sputtering pressure due to the enhancement of point defects such as zinc and oxygen vacancies. The dominant neutral donor to bound exciton emission with narrow full width at half maximum implies the high optical quality of the nanostructures irrespective of argon sputtering pressure. The characteristic of visible emission at 3.01 and 2.28 eV provides a strong evidence for the existence of zinc and oxygen vacancies in ZnO nanostructures. (c) 2013 Elsevier Ltd. All rights reserved.