Emission characteristics of ZnO nanorods on nanosilicon-on-insulator: competition between exciton-phonon coupling and surface resonance effect

We investigated the optical properties of ZnO nanorods on nanosilicon-on-insulator using variable temperature photoluminescence (PL) spectroscopy, and explored the contribution of exciton-phonon coupling and surface resonance effect on the emission characteristics of the nanorods. The low-temperature (<100 K) PL spectra revealed different strengths of exciton-phonon interaction for nanorods of different surface structures. The exciton-phonon coupling strength was stronger for nanorods of rougher surfaces with enhanced contribution of longitudinal optical phonon replicas of free exciton. Despite exhibiting different coupling strengths of exciton-phonon interactions, the room-temperature PL showed an unchanged energy position at 3.28 eV for nanorods of different surface structures. The unchanged energy position of band-edge emission was caused by the competitive effect of the surface defects induced exciton-phonon interaction and the surface resonance effect in faceted nanorods.