Study On Synthesis Of Graphene By Chemical Vapor Deposition

Graphene, a stable two-dimensional(2D) material built of a single layer of sp2-hybridized carbon atoms, has attracted wide interest for promising applications in the fields of electronics, photonics and optoelectronics. Synthesis of high-quality graphene in low cost is the key for its comprehensive applications. So far, chemical vapor deposition (CVD) is generally considered as one of the best methods to synthesize large-area, high quality graphene films at low cost. In principle, the quality and performances of CVD-grown graphene is largely correlated to the growth conditions, such as substrate, carbon source, temperature, pressure, and so on. In this thesis, we concentrate on the controllable synthesis of graphene by chemical vapor deposition. The influence of different growth condition on morphologies, structures, optical and electrical properties of graphene is discussed. The main results are listed as follows:1.We demonstrated a novel ternary alloy (Cu2NiZn) to synthesize monolayer graphene with high quality and fascinating electrical performance using a liquid carbon precursor cyclohexane by low pressure CVD. Samples were characterized by Raman spectroscopy, Raman mapping, Atomic Force Microscope(AFM), Transmission Electron Microscopy (TEM) and Transmittance, which revealed the graphene on Cu2NiZn was monolayer with better uniformity and higher transmittance in contrast to those on Cu and Cu-Ni substrates. Besides, we fabricated back-gate FETs with graphene grown on different substrates. The test results indicate higher mobility of graphene/Cu2NiZn compared with Cu and Cu-Ni. showed higher mobility in contrast to those on Cu and Cu-Ni. Density functional theory (DFT) calculations confirm that Cu2NiZn substrate possesses higher catalytic activity for the dehydrogenation and nucleation.2. We demonstrated the low temperature, large area growth of ultrathin graphene-like films by atmospheric pressure chemical vapor deposition under atmospheric pressure on various substrates. The characterizations revealed that the low-temperature-grown carbon films were consisting of few short, curved graphene layers and thin amorphous carbon films. Notably, the low-temperature grown films exhibited over 90% transmittance at wavelength range of 400-750 nm and great conductivity. This low-temperature CVD growth method may offer a facile way to directly prepare visible graphene-like films on various substrate surfaces that are compatible with temperatures(500-600℃).3. Using methane as the carbon source, single-crystal graphene was successfully grown on copper by controlling the growth temperature, growth time, gas flow rate and other parameters.. The characterizations revealed single crystal graphene with different morphologies and properties formed on the surfaces of copper under different states.