Characteristics of controllable-shape well-aligned zinc oxide nanorods synthesised by microwave-assisted heating

A microwave-assisted heating method for growing well-aligned zinc oxide (ZnO) nanorods on the ZnO/silicon (Si) substrate is developed. For ZnO nanorods growth, a thin ZnO seed layer was deposited on an Si substrate by sputtering technique. The ZnO nanorods grown on the ZnO/Si substrate were synthesised in aqueous solution mixed with zinc nitrate hexahydrate and hexamethylenetetramine (HMTA) under microwave heating. The scanning electron microscopy (SEM) images and X-ray diffraction results exhibit that the ZnO nanorods with hexagonal phase, single crystalline, and highly oriented along (002) plane are obtained successfully. SEM images also show that the morphology and diameter of the synthesised ZnO nanorods can be controlled by adjusting the molar ratio of Zn(NO₃)₂·6H₂O to HMTA. The Raman scattering results evidence the vertical well-aligned ZnO nanrods with larger diameter are strain-free. The investigations of the photoluminescence spectra suggest that the ultraviolet emission peak of the synthesised ZnO nanorods depending on its controllable diameter would be applicable for various nanodevice fabrications.