Development and Investigation of Direct Growth of Graphene on Arbitrary Oxide Substrates

• Main Authors: YEN, WEN-CHUN, 顏文群
• Other Authors: CHUEH, YU-LUN
• Format: Others
• Language: en_US
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/06280784911505591201

博士 === 國立清華大學 === 材料科學工程學系 === 102 === In 2004, graphene, a stable 2D material with only one atomic thickness, has been first synthesized from a highly ordered pyrolytic graphite by mechanical exfoliation. Due to the two-dimensional nature, graphene exhibits a lot of outstanding physical properties such as extremely high mobility for both electrons and holes, extremely high thermal conductivity, and extremely high optical adsorption rate and is considered as one of candidates of materials for the next generation optoelectronics industry. Until today, many different processes to synthesize graphene have been developed. The chemical vapor deposition process by using Cu or Ni as the catalysts is the most famous process since it can grow graphene with high quality and large area by adjusting the growth conditions. Unfortunately, the graphene grown on the Cu or Ni foils/films by the CVD process needs an extra transfer process to transfer the graphene onto oxide substrate for devices. The transfer processes are complex and usually damage graphene to significantly decrease the quality of graphene. In this thesis, development of new processes on directly growing graphene on the arbitrary metal oxide substrates by using microwave heating process and Ni vapor-assisted CVD processes, respectively. Due to the strong dipole nature, SiC was used as the susceptor to absorb microwave and transfer into heat to heat the α-C/Ni/SiO2 sample prepared by E-xbeam evaporation. Since the microwave can be focused on the target, the process is fast with high temperature increase/decrease rate. The balance between oxidation and reduction by oxygen and amorphous carbon keeps the Ni layer to remain the metallic nature and allows graphene segregate on the surface. Besides, the highly order graphite was found at the interface between Ni and SiO2 with the almost 80% transformation ratio from amorphous carbon. For the graphene deposition process, Ni vapor was used as a gas phase catalyst to decompose the methane and release carbon atoms during the annealing process. The thickness of graphene can be tuned linearly by adjusting the deposition time. In addition, we also demonstrated direct growth of graphene on a high aspect ratio Si nanorod arrays. The endurance of field emitted test also shows the high stability performance of this graphene/Si nanorod hybrid structure even under a large current. Depending on the self-assembly process, we also introduce a boron vapor into the growth system to achieve the boron doping of the graphene during the graphene deposition to change the work functions by carefully adjusting the deposition rate of graphene.