Synthesis and characterization of graphene/carbon nanotube hybrid: effects of Ni catalyst thickness and H-2 flow rate on growth and morphological structure

We reported a combination of the unique properties of (2D) graphene and (1D) carbon nanotubes (CNTs) by synthesizing a novel graphene/CNTs hybrid structure. Graphene and CNTs were synthesized by a two-step chemical vapor deposition (CVD) system. In the first step, multilayer graphene (MLG) was grown on nickel substrates by changing the methane gas flow rate and growth time. In the second step, the CNTs were then grown on the synthesized MLG surface previously. Both the Ni catalyst film thickness and H-2 gas flow rate were changed to investigate their effects on the growth densities and average diameters of the hybrid structures. Structural and morphological analysis of both MLG and MLG/CNT hybrid structures were determined using X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), energy-dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and Raman analysis. As the Ni catalyst film thickness was increased, CNTs grew more densely on the MLG. It was observed that CNTs with smaller diameters and longer lengths formed with increasing H-2 gas flow rate. This hybrid structure is useful in electronic, optoelectronic, and energy storage applications.