A comparison of ZnO nanowires grown using hexamethylenetetramine and ammonium hydroxide on Al:ZnO nanoparticle seed layer

ZnO is a low-cost material which can be easily manipulated into different morphologies using hydrothermal synthesis. In this study, ZnO nanowires are grown using hexamethylenetetramine (HMTA) and ammonium hydroxide as bases for the hydrothermal method. The growth time and temperature are varied and the nanowires are characterised structurally and optically. Electron microscopy images of the nanowires show that ammonium hydroxide forms pointed tips whereas HMTA forms flat tips. This is attributed to the chelating properties of HMTA. X-ray diffraction patterns show strong c-axis preferred orientation exhibited by ammonium hydroxide grown nanowires with large variability in crystallinity, whereas HMTA produced nanowires that show random orientation. The optical band gap is observed to decrease with solution temperature for both types of bases, however surface oxygen vacancy defects are observed in photoluminescence measurements of the ammonium hydroxide grown nanowires.