Research On Synthesis And Mechanism Of Graphene Grown Directly On SiO₂ Dielectric Substrates

Graphene is a perfect two-dimensional carbon material with compact honeycomb structures, consisting of sp²-bonded carbon atoms. Considerable works have been devoted to growing graphene on metal catalysts by CVD method. However, for further application, we have to transfer the as-grown graphene onto another suitable substrate from the metal catalyst surface, which is a complicated process. This transfer process is inevitable to result in various contaminations, wrinkles, defects, cracks inside graphene, which can decrease the quality and properties of obtained graphene film. Therefore, it is indispensable to grow graphene films directly on dielectric substrates without any transfer process. Nowadays,those methods which grow graphene directly on dielectric substrates meet two questions, including long growth time and high growth temperature. In this thesis, we discuss a series of effective methods to grow graphene directly on SiO₂/Si substrates.Large-area and continuous graphene film has been grown directly on SiO₂/Si substrates by a fast growth method. This method avoids the complicated transfer process from the metal surface onto the dielectric substrates. Instead of the traditonal precusor（CH4） which is difficult to decompose, ethanol is used as carbon source which is easier to decompose at high temperature. After optimizing the related experimental condition, a large area（centimeter level） and continous graphene can be formed within shorter time using this CVD method. field effect transistor（FET） is fabricated and the hole mobility is in the range of 1.2^-19.1 cm²·V^-1·s^-1.The growth mechanism of catalyzing ethanol to synthesis graphene is discussed in term of growth kinetics and thermodynamics. The morphology, chemical composition and structure of obtained graphene in different stages are also analysised.Large-area and continuous graphene film on SiO₂/Si substrates is formed without hydrogen etching. Contrasted to CH4, methanol itself can easily decompose into water（an etching reagent）. Different reaction conditions on the quality and structure of the obtained graphene are discussed, including growth temperature, growth time, and the concentration of hydrogen. Similarly, the FET of graphene is fabricated and its hole mobility is measured in the range of 14.1-74.0 cm²/V·s.