– Studies of the Chemical Vapor Deposition Method of Generating Graphene –
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ABSTRACT
Since the pioneering report of the discovery of graphene in 2004 by Novoselov et al, scientists and researchers worldwide have carried out in-depth investigations in this new family of carbon because of its myriad properties and potential applications. The synthesis of the novel nanoscale material is the main target in current material science.
This study investigates the effect of different types of carbon source and catalyst for the production of large-area, single/few crystalline layer of graphene via chemical vapor deposition (CVD) method.
Four types of carbon source i.e. acetylene, methane ethylene and benzene were used for the synthesis of graphene. The catalysts used in the synthesis of graphene are cobalt and nickel.
The as-synthesized graphene were characterized by scanning electron microscopy (SEM),field emission scanning electron microscopy (FESEM), Raman spectroscopy and atomic force microscopy (AFM).
This analysis also confirmed that all the prepared catalysts were active for the production of graphene. SEM/FESEM analysis revealed good morphologies of graphene formed with different catalysts and carbon source.
Raman spectra revealed that benzene might be a better precursor to produce graphene based on the positions of the G-band and 2D-band peaks.
Generally, this research has been successful in producing graphene from different hydrocarbon sources depending on the catalysts used.
1.1 INTRODUCTION
1.1.1 Carbon Materials
Group IVA, consists of carbon (C), silicon (Si), germanium (Ge), tin (Sn) and lead (Pb). Carbon is the chief constituent of coal, and it forms the backbone of the hydrocarbon molecules in oil and natural gas.
The element, carbon, is one of the most versatile elements in the periodic table in terms of the number of compounds it may form.
Carbon also occur widely in carbonate rocks, such as limestone, dolomite and marble. Basically, carbon has 3 allotropes i.e. diamond, carbon nanotubes and fullerene. Each of these carbon allotropes has different features due to the bonding between carbon atoms.
Carbon has four valence electrons with an electronic configuration of 1s22s22p2. It may form virtually an infinite number of compounds.
This is largely due to the types of bonds it can form and the number of different elements it can join in bonding.[1]
Carbon Bonding
Bonding in any element will take place with only the valence shell electrons. Carbon may form single, double and triple bonds. The valence shell electrons are found in the incomplete, outermost shell.
In the ground state (lowest energy state), two of the electrons are in the 1s orbital (K shell), two are in the 2s orbital (L shell) while the third pair is in the 2p orbital (L shell).
The 1s electrons are considered to be the core electrons and are not available for bonding. There are two unpaired electrons in the 2p orbitals, so if carbon were to hybridize from this ground state, it would be able to form at most two bonds.
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