Formation of CuO nanowires by thermal annealing copper film deposited on Ti/Si substrate

Nanowires of various inorganic materials have been fabricated due to the realization of their applications in different fields. Large-area and uniform cupric oxide (CuO) nanowires were successfully synthesized by a very simple thermal oxidation of copper thin films. The copper films were deposited by electron beam evaporation onto Ti/Si substrates, in which Ti film was first deposited on silicon substrate to serve as adhesion layer. The structure characterization revealed that these nanowires are monoclinic structured single crystallites. The effects of different growth parameters, namely, annealing time, annealing temperature, and film thickness on the fabrication of the CuO nanowires were investigated by scanning electron microscopy. A typical procedure simply involved the thermal oxidation of these substrates in air and within the temperature range from 300 to 700 degrees C. It is found that nanowires can only be formed at thermal temperature of 400 degrees C. It is observed that the growth time has an important effect on the length and density of the CuO nanowires, whereas the average diameter is almost the same, i.e. 50 nm. Different from the vapor-liquid-solid (VLS) and vapor-solid (VS) mechanism, the growth of nanowires is found to be based on the accumulation and relaxation of the stress. (C) 2011 Elsevier B.V. All rights reserved.