Thermodynamic behaviors of excitonic emission in ZnO nanorods grown by pulsed laser deposition

We investigated the thermodynamic behaviors of the exciton emission in ZnO nanorods that had been grown by laser ablation. The ZnO nanorods exhibited a clear luminescence peak from the neutral donor-bound exciton (D0X), which persisted near room temperature. Through analyzing temperature-dependences of photoluminescence properties, we found out insignificant thermal-quenching of D0X, arising from the large donor binding energy (i.e., EbD(NR) ~ 51.1 ± 7.3 meV). A small discrepancy of EbD(NR) from ZnO bulks' values (i.e., EbD(Bulk) = 53 - 72 meV) is associated with inhomogeneous thermal-broadening factors such as defect-scattering at the surface of the nanorod. Despite of inhomogeneous thermal-broadening, the ZnO nanorods still have a high luminescence efficiency because of the weak homogeneous thermal-broadening effect (i.e., low exciton-phonon coupling).