Facile Synthesis of 1D and 2D Zinc Sulfide Nanostructures on Multi-Layered Graphene

Abstract

ZnS nanostructures have been fabricated over multi-layered graphene substrate via chemical vapor deposition technique. A controllable morphology of grown ZnS nanostructures, including (1D) nanowires, (2D) discs and nano-flakes were achieved by direct carbo-thermal evaporation of (1:1) ZnS and graphite powders mixture. The substrate location and therefore its temperature was found as a crucial growth parameter, which controls the morphology of the grown ZnS Nanostructures. The average diameter of the ZnS 1-D nanowires, at T= 400 °C, 2-D planar filling nano-discs, at T=300 °C, are 0.418 ± 0.007 μm, 0.600 ± 0. 020 μm respectively. At lower substrate temperature, <300 °C, a periodic round shaped features or flakes with some nanowire at their edges were formed due to nanodiscs amalgamation. This is because at a lower temperature, higher liquid instability leads to more nucleation sites and high conversion rate from liquid to solid state and therefore small nano-discs will merge to form larger flake structure. All products are cubic sphalerite ZnS in structure and with preferentially intense (111) planes. The lattice parameter for (220) planes was 5.72 A with 5.92% strain % clearly indicate that they are in tensile stress region. Raman was utilized to define the existence of graphene layers and the ZnS nanostructures (Magnified range100-700 cm-1) on top of multigraphene layers before and after growth process. In addition, ZnS nanostructures PL emissions of violet and cyan-blue centered at 3.23ev and (2.41-2.53ev) respectively were detected and attributed to defects such as Zn2+ vacancies, S2− interstitials, and dislocations. Graphene-based inorganic hybrid nanostructures deliver several potential applications in optoelectronics and nanoscale electronics such as photodetectors, photovoltaic and optical devices.