On the growth of copper oxide nanowires by thermal oxidation near the threshold temperature at atmospheric pressure

Abstract

This study focuses on the growth of copper oxide nanowires networks (CuO NWs) close to the onset temperature, found to be 310 ℃. The NWs were obtained by thermal oxidation in air of polycrystalline copper foils on hot plate. The investigated oxide layers with the NWs network on their surface grown between 200 ℃ and 440 ℃, were characterized by: SEM-EDX, STEM-EDX, XRD, and micro-Raman techniques. The accurate determination of copper content in self-exfoliated oxide sheets is above the stoichiometric concentration. XRD reveals nano-crystallites of 20–40 nm, in Cu2O phase of thick oxide sheets located close to the oxide-substrate interface. Statistical data on the average length of the NWs versus annealing time indicates unexpected early saturation in between 10 and 40 min at 320–340 ℃. A semi-empirical model proofs quantitatively that the emerging delays of the NWs relative to the start of copper oxidation determine the plateau of the average length versus time. The excess concentration of copper found in the cuprous oxide layer is cautioned to accompany the early saturation effect having critical restrictions regarding the oxidation time and temperature. This study sustains the development of control and monitoring methods, applied to the growth of CuO NWs.