Optical properties of ZnO nanowires grown by thermal evaporation

Abstract

The mass production of wurtzite-type structure ZnO nanowires were synthesized by a simple and rapid method based on the thermal evaporation of metal zinc pellets without the use of noble metal catalyst. The PL spectrum at room temperature shows a strong near band gap emission (NBE) peak and a weak deep-level emission (DL) peak, which implies its good crystallinity and high optical quality. The DL and NBE emission are considered to originate from the singly ionized oxygen vacancy and the overlap of free exciton and free-to-band emission respectively by electron paramagnetic resonance (EPR) spectroscopy and low temperature photoluminescence. The coupling parameters of exciton-acoustic phonon and of exciton-longitudinal-optical phonon were determined as 63.44 μeV/K and 898 meV, and 251 K for Einstein temperature according to the temperature dependence of free exciton emission spectra.