Suppression of pinhole defects in hydrothermally grown ZnO nanorod arrays

Zinc oxide (ZnO) is a versatile semiconductor used in a wide range of electronic and energy-related applications. Hydrothermal growth of vertically aligned ZnO nanorodnanorods from seeded substrates offers a low-cost and scalable route to forming nanorod arrays. However, the process often produces pinholes and voided regions when gas bubbles nucleate and become pinned at the substrate surface during growth. Here, we show that a combined protocol of air plasma surface activation, near vertical substrate orientation and solution degassing which greatly suppresses pinhole defects. The protocol reduced the pinhole area coverage from 1.18% to 0.01%, representing an approximately 118-fold decrease, or just over two orders of magnitude reduction. Removing these defects improves the uniformity and homogeneity of the nanorod array across the substrate. Overall, this defect-mitigation approach improves array quality and coverage, enabling more reliable ZnO device fabrication and enhancing performance by reducing pinhole-driven nonuniformity and failure pathways.