Temperature-dependent photoluminescence properties of C(carbon)-aided ZnO nanorod arrays on (1 0 0) Si substrate

Abstract

We investigate the photoluminescence (PL) spectra of ZnO nanorod (NR) and C(carbon)-aided NR arrays from 10 to 300 K. The activation energy of the donor-bound exciton of the ZnO NRs was determined to be 11.3 meV ranging over 10–300 K. The decreasing behavior of the PL intensity for the C(carbon)-aided ZnO NRs exhibited two activation energies, i.e., 3.2 and 65.8 meV at T < 70 K and T > 70 K, respectively. The activation energy for the donor-bound exciton decreased because of stronger quantum confinement in the C(carbon)-aided ZnO NRs than that of the ZnO NRs. We attribute these results to lower lattice mismatch, a larger surface-to-volume ratio, and the dense structure of the vertically orientated hexagonal pillars with flat faceted surfaces in the C(carbon)-aided ZnO NRs. A considerable exciton binding energy of 65.8 meV from the C(carbon)-aided ZnO NR arrays produced luminescence stably at 300 K. In addition, PL spectra demonstrated that the luminescence intensities of the C(carbon)-aided ZnO NRs were higher than that of the ZnO NRs because of weak exciton-phonon coupling. The higher PL intensities of the C(carbon)-aided ZnO NRs suggest that these structures might feature improved performance in optoelectronic nano-devices manufactured from ZnO NRs.