Self-Etching-Induced Morphological Evolution of ZnO Microrods Grown on FTO Glass by Hydrothermal Method

In this research, the zinc oxide (ZnO) microrods were grown by hydrothermal method on fluorine-doped tin oxide (FTO) glass functionalized by self-assembled monolayer of octadecyltrimethoxysilane (ODS; CH3(CH2)17Si(OCH3)3). The sharp-tip or polygonal shape with specific facets at the top end of ZnO microrods can be obtained by post retention at low temperature. The morphologies were characterized by the field-emission scanning electron microscope (FESEM) and transmission electron microscopy (TEM). The results confirm that the morphology change at the top end is due to self-etching. The mechanism responsible for the formation of various top-end morphologies was proposed. The specific facets that left after 6-h retention were identified. The room-temperature micro-photoluminescence spectra showed a strong ultraviolet emission at 387 nm, and a broad emission at a range of from 500 to 700 nm. The morphology change also influences the photoluminescence (PL) spectra. A satellite peak in the UV emission spectra was observed. The peak may be attributed to the morphology effect of the microrods.