Modelling study and tuning of graphene growth on Cu foil by CVD method

Abstract

Graphene as a two-dimensional material has attracted more and more interests due to its remarkable properties. Nowadays chemical vapor deposition (CVD) on Cu foil is the most popular method to achieve large area, high quality and layer number controllable graphene films. The understanding of the graphene/Cu interaction is not only important for successful graphene transfer onto other applicable substrates but also for tuning the growth behavior during the synthesis step. In this PhD thesis, we first investigated the decoupling process of graphene from Cu foil by oxidation-assisted water intercalation. Our findings reveal that the decoupling process initiates from the graphene edges and defect sites, assisted by interfacial copper oxidation and water intercalation due to Cu galvanic corrosion. During this process, interfacial oxidation acts as the dominating role. In the second part, we established a facile strategy to control the graphene nucleation by tuning the gas flow rate and restricting gas diffusion in semi-open space. In addition, by applying the Cu/quartz substrate, the dehydrogenation of carbon precursor is greatly enhanced leading to boosted graphene growth rate while not affecting the nucleation density. With this method, sub-centimeter sized single crystal graphene grains can be obtained in one hour. Finally, we demonstrated that epitaxial graphene growth on copper can be achieved by simply turning off hydrogen during the growth. We find that the graphene grains grown on both Cu (111) and Cu (110) align in one orientation, while two orientations with ~30° rotation are obtained on Cu (100). This epitaxial growth is achieved due to stronger edge interaction between graphene and Cu substrate. On the other hand, the more surface oxygen modifies the growth mechanism from attachment limited to diffusion limited resulting in non-hexagonal grain shapes.

Date of Award	2017
Original language	English
Awarding Institution	The Hong Kong University of Science and Technology