Detailed Study on Photoluminescence Property and Growth Mechanism of ZnO Nanowire Arrays Grown by Thermal Evaporation

The photoluminescence (PL) property and growth mechanism of ZnO nanowires, which are essential to both fundamental and applied studies, are not yet well understood. Here extensive investigations have been carried out to deeply understand the two issues. At first, ZnO nanowire arrays are fabricated on bare glass substrate via a noncatalytic thermal evaporation method. Afterward, the PL measurements reveal that the emission peaks located at 405 and 616 nm are related to the Zn vacancy defect, and the red peak located in the region between 750 and 800 nm has relations with the interaction between the Zn vacancy and Zn interstitial defects. Detailed experiments show that the oxygen flux plays a very important role in the morphology evolution of the as-grown products, which change from nanoflakes to nanowires and finally to nanonails with the increase of oxygen flow rate. The competition between the axial growth and the radial growth results in the morphology evolution. Finally, a two-stage vapor-solid (VS) growth model is proposed to interpret the growth behavior of the ZnO nanowires. Our results have made a positive progress toward the PL property and growth mechanism of ZnO nanowires.