Growth and Characterization of Graphene and Its Derivatives

  • 凃 嘉豪

Student thesis: Doctoral Thesis

Abstract

The aim of this research is to investigate the growth mechanism of the synthesis of graphene related materials by various methods The graphene related materials include monolayer graphene snowflake porous graphenic carbon film composite of carbon nanorod on porous graphenic carbon film and graphene nanowalls First chemical vapor deposition is employed to grow large single-domain graphene snowflakes (> 0 5 mm2) on Cu foil by crossing numerous Cu grain boundaries underneath The orientation of the graphene snowflake branches is preserved when crossing the Cu grain boundaries as evidenced by Raman spectra and transmission electron microscopy analysis Diffraction patterns and scanning electron microscopy images reveal a relationship between the growth front and the orientation of graphene snowflakes The graphene snowflake branch portions before and after crossing a Cu grain boundary show similar effective field-effect mobilities confirming that the orientation did not change Diffraction patterns of graphene and electron backscattering diffraction maps of Cu grains are used to study graphene lattice overlap below Cu grains The orientation of Cu grains has little influence on the growth of top graphene snowflakes probably due to the weak bonding interaction between Cu grains and graphene constraining the growth of graphene snowflakes at temperatures close to the melting point Second a method is developed for growing three-dimensional hierarchic structures of porous graphenic carbon film/ hollow carbon nanorods where porous graphenic carbon film is first synthesized followed by growth of carbon nanorods Porous graphenic carbon films were synthesized by solid-state diffusion on nickel thin film By annealing an amorphous carbon layer deposited underneath a nickel thin film at elevated temperatures the porous graphenic carbon film forms on top via carbon diffusion and precipitation from the grain boundaries of the nickel film Hollow carbon nanorods can then be grown on the pore edges of the porous graphenic carbon film by chemical vapor deposition without catalysts It is speculated that the dangling bonds of the carbon atoms on the pore edges of the graphene layers might be responsible for the nucleation of the hollow carbon nanorods The microstructures and growth mechanisms of both porous graphenic carbon film and hollow carbon nanorods are characterized and discussed in detail Finally carbon nanowalls were successfully grown on Si(001) wafer by direct-current plasma enhanced chemical vapor deposition Carbon nanowalls standing structure of graphene sheets are vertical to substrate Heteroepitaxial nucleation of {002} graphene sheets on {111} facets of plasma treated (100) silicon is confirmed by high-resolution transmission electron microscopy Lattice mismatch by 12% is compensated by tilting the graphene {002} with respect to silicon {111} and matching the silicon lattice with fewer graphene layers The interlayer spacing of graphene sheets near the silicon surface is 0 355 nm which is larger than that of AB stacked graphite and confirmed as AA stacked graphitic phase A strong Raman peak corresponding to silicon-hydrogen stretch vibration is detected by 633 nm excitation at the early stage of graphene nucleation indicating the silicon substrate etched by hydrogen plasma With these analyses the growth mechanism is also proposed
Date of Award2015 Feb 3
Original languageEnglish
SupervisorChuan-Pu Liu (Supervisor)

Cite this

Growth and Characterization of Graphene and Its Derivatives
嘉豪, 凃. (Author). 2015 Feb 3

Student thesis: Doctoral Thesis