Advanced synthesis method for high quality graphene as a channel material for next generation transistor

Abstract

This dissertation focuses on the investigation of graphene synthesis which can be utilized as a channel material of advanced field effect transistor. For that purpose, graphene synthesis using carbon implantation is introduced to improve the reproducibility of synthesis method, and Ni/rGO/SiO2 stacked structure is also suggested for the formation of wrinkle free graphene. For the synthesis of graphene using carbon ion implantation, Carbon ions were implanted in a nickel thin film and after a subsequent rapid thermal annealing, they segregated on the surface, forming a graphene layer. The dependence of graphene synthesis on process conditions, including the carbon implantation dose, RTA temperature and time, were investigated. The graphene shows quality comparable to the best reported CVD graphene. It was also found local growth of graphene through local implantation requires stringent control of the process chamber conditions in order to avoid growth of graphene on unimplanted regions. And, for the method utilizing a reduced graphene oxide (rGO) interfacial layer between the metal film and the wafer substrate, the rGO interlayer releases the residual stress of the metal thin film and thereby suppresses stress-induced metal grain growth. This technique makes it possible to use much thinner nickel films, leading to a dramatic suppression of RMS roughness (~3 nm) of the metal surface even after high temperature annealing. It also endows excellent control of the graphene thickness due to the reduced amount of total carbon in the thin nickel film. The synthesized wrinkle-free graphene layer exhibits excellent thickness uniformity (95% coverage of monolayer) and very high carrier mobility of ~15000 cm2/Vos. As further works, the synthesis of wrinkle free graphene on Cu substrate will be conducted. Since Cu substrate has better reproducibility of forming monolayer graphene than Ni substrate, winkle free graphene formation on Cu substrate should be conducted for the r...