New routes to copper sulfide nanostructures and thin films

Abstract

The copper(II) complex of 1,1,5,5-tetra-iso-propyl-2-thiobiuret [Cu(SON(CNiPr2)2)2], has been synthesized and its single crystal X-ray structure determined. The complex has been used as a single source precursor for the preparation of copper sulfide nanoparticles by solution thermolysis. The nanoparticles synthesized had various morphologies including spherical, hexagonal disks, and trigonal crystallites; depending on the reaction temperature, concentration of the precursor and the growth time. Thermolysis experiments in oleylamine produced Cu7S4 nanoparticles as a mixture of roxbyite (monoclinic) and anilite (orthorhombic) phases. Pure anilite Cu7S4 nanoparticles were obtained when a solution of precursor in octadecene was injected into hot oleylamine whereas, djurleite Cu1.94S nanoparticles were obtained when a solution of the precursor in oleylamine was injected into hot dodecanethiol. The optical properties of the pure anilite Cu7S4 phase and the djurleite Cu1.94S are consistent with indirect band gap materials. The complex was also used for the preparation of copper sulfide thin films by aerosol assisted chemical vapour deposition (AACVD). Powder X-ray diffraction (p-XRD) patterns of the thin films showed the deposition of a mixture of cubic CuS2 and hexagonal Cu2S phases at all temperatures. Scanning Electron Microscopy (SEM) of copper sulfide films showed spherical crystallites from reaction at 280 °C, cuboids at 320 °C and plate like crystallites between 360 and 400 °C. Transmission Electron Microscopy (TEM) of material scratched from thin films showed nanoplates of copper sulfides with 25–30 nm in width.