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.