Our aim is to grow zinc oxide (ZnO) nanowires on various semiconductor substrates by hydrothermal synthesis. To obtain porous silicon, electrochemical etching on the silicon substrate was performed. Electrochemical etching is the process of etching where a cathode, anode and an electrolyte are used. Here, we etch the samples using 1:3 HF: Acetonitrile and 1:3 HF: Ethanol. No nanowire growth is observed on the samples etched with HF: Acetonitrile. Very few nanowires are formed on the samples etched with HF: Ethanol. Very dense growth of nanowires is observed on non-porous silicon substrates.

An equimolar mixture of Hexamethylenetetramine and Zinc Nitrate Hexahydrate is prepared and constantly stirred for about 5--10 min to obtain a pH ranging from 6.5--6.85. The samples are then dipped in the equimolar mixture of Hexamethylenetetramine and Zinc Nitrate Hexahydrate maintained at a constant temperature. At a longer growth rate, i.e. at after 16 hours we could grow nanowires on the porous silicon samples. The samples were then characterized using Scanning Electron Microscopy (SEM) and a uniform growth of Nanowires was obtained.