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 Cu_1.94S 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 Cu_1.94S 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.