Tuning Optoelectronic Properties Through In‐Plane Arrangement and Point Defects in ZnO Nanorods as Prepared by Room‐Temperature DC‐Unbalanced Magnetron Sputtering

Abstract

Electronic and optical properties of ZnO nanorods grown by room temperature dc-unbalanced magnetron sputtering are studied. As a comparison, ZnO thin film is deposited as well. Surface morphology images and X-ray diffraction patterns show that ZnO nanorods are successfully grown with hexagonal wurtzite structure and the diameter varies from 50 to 90 nm. Using photoluminescence spectroscopy, the presence of oxygen vacancy (V O ) is observed in ZnO nanorods sample. Furthermore, current-voltage measurement shows that ZnO nanorods have a lower dark current due to V O -induced oxygen adsorption, which confirms the presence of a high potential barrier related to the V O . It is found that ZnO nanorods give photocurrent to dark current ratio almost 20 times higher than that of the thin film at bias voltage of 5 V. Here, the performance of ZnO nanorods with the metal-semiconductor-metal (MSM) and p-n heterojunction configuration is also compared. The photosensitivity of MSM configuration is six times higher than p-n heterojunction. These results are important to improve the functionality of nanostructured ZnO by controlling the structure and point defects for nano-scale optoelectronic application.