Optical and electrical performance of HfO2 coated ZnO nanorod arrays

In this paper, we demonstrate the optical and electrical performance of ZnO nanorod arrays after surface passivation. The material of larger band gaps (HfO2) was chosen for the surface passivation layer through atom layer deposition (ALD), in order to confine the carriers within the core material efficiently. In the case of nanorods with high defects, HfO2 coating treatment not only improved near band edge (NBE) but also greatly enhanced the defect luminescence, while in the case of nanorods with low defects, surface coating suppressed defect luminescence and promoted the NBE emission as well as electrical performance therein. PL investigation at 10 K displayed that after surface coating phonon related emission was confined along c-axis and the exciton emission related to surface states was largely restrained. Therefore, it's suggested that surface passivation of ZnO nanorod arrays decreases the surface defect, enhances the side confinement of nanorod, and thus improves the optical and electrical performance efficiently.