Preparation of copper nanowires and thermal oxidation behaviour in dry oxygen

Copper (Cu) nanowires are a promising functional and structural material in electronics, optoelectronic devices and integrated circuits. The preparation and thermal stability of Cu nanowires are crucial for the functional realisation and performance stability of related devices. In this work, the authors particularly prepared Cu nanowires by a two-step approach and further studied the thermal oxidation behaviour of Cu nanowires in dry oxygen. It was found that the as-prepared Cu nanowires have a good (111)-oriented single crystal structure with a smooth and clean surface. With the increase of annealing temperature and time, the Cu nanowires were oxidised gradually in dry oxygen and the crystal phase of Cu nanowires underwent the evolution of Cu (111)→Cu₂O (111)→CuO (−111)+(111). Furthermore, when the temperature was not higher than 400°C, the as-formed Cu₂O and CuO layers or nanowires were slightly crystallised or nearly amorphous. However, when the temperature was higher than 400°C, the as-formed CuO nanowires were greatly crystallised. It was further observed that the oxidation of Cu nanowires arose from the wire surface and formed a non-dense, nearly amorphous layer of Cu₂O nanoparticles therein. Such Cu₂O layer on the surface of Cu nanowires greatly reduces optical transmittance.