Fabrication of size-tunable graphitized carbon spheres with hierarchical surface morphology on p-Si (100) by chemical vapour deposition

Abstract

Graphitized carbon spheres (GCSs) with varied diameters (500 nm to 4.5μm) and hierarchical surface morphologies were successfully produced on iron-particles coated silicon (100) substrate at 750°C by chemical vapour deposition (CVD). By varying the mass flow rate of the precursor gasses and the method of catalyst coating on silicon (100), GCSs with varied diameters and differing morphologies were obtained. When the mass flow rate of the precursor gasses was altered, the mean diameter of GCSs increases until it reaches an optimum value (~3.1µm) suggesting a size-tunability of GCSs. Changing the catalyst coating method on silicon (100) from dip coating to spin coating produces larger-sized GCSs on silicon (100). Field Emission Scanning Electron Microscopy (FE-SEM) images show that GCSs possess a regular and uniform shape with the formation of a hierarchical surface morphology. The analysis of the variation of the surface roughness laterally across the substrate showed that the increased surface roughness resulting in from catalyst spin coating increases the mass transfer rates leading to the formation of larger-sized GCSs on Si (100). Raman spectroscopy and X-ray diffraction spectra obtained from the catalyst spin-coated and dip-coated samples confirmed the presence of graphitized hexagonal carbon networks in CSs. The surface functionality of GCSs was examined using FTIR spectroscopy. Synthesized GCSs were then used to fabricate an anode material in sodium ion rechargeable batteries and the performance of GCSs as an anode material in rechargeable battery system was investigated and the results obtained are also discussed here.