Gas-phase substitution synthesis of Cu1.8S and Cu2S superlattice nanowires from CdS nanowires

Abstract

Single-crystalline wurtzite CdS nanowires underwent gas-phase substitution to form unique superlattice cubic Cu1.8S (digenite) and hexagonal Cu2S (chalcocite) structures, using thermal evaporation of CuCl2 at 500 similar to 600 degrees C. The Cu1.8S nanowires consisted of superlattices along the < 111 > direction, with controlled growth direction ([110], [211], [100], [111]) and superlattice periods of 1.6 and 1.9 nm. As the temperature decreased, the growth direction evolved from [100] to the higher surface-energy [110] or [211] directions, with longer superlattice periods. The Cu2S nanowires also exhibited a superlattice along the [0001] growth direction, with a periodicity of 2.7 nm and could be irreversibly converted into superlattice Cu1.8S by electron-beam irradiation.