講演情報
[15a-K207-3]Investigation of Twist Angle Variations in Large-Scale High-Quality Hexagonal Few Layer Graphene
〇(P)Sengottaiyan Chinnasamy1, Kazunori Hirosawa1, Yuta Kurachi1, Masanori Hara1, Masamichi Yoshimura1 (1.Toyota Tech. Inst.)
キーワード：
Graphene、Raman、AFM
Despite the large single-crystal graphene is highly desired and important for the applications of graphene in electronics, it is still a challenge to precisely control the nucleation site of graphene to develop wafer-scale high-quality graphene. Herein, we synthesized millimeter-scale high-quality graphene stacked in a few layers on copper (Cu) foil by chemical vapor deposition.
In detail, a Cu-foil was carefully annealed in Ar and H2 atmosphere to synthesize graphene to remove impurities and increase grain size. Then methane (CH4) was introduced at 1035 °C to grow high-quality graphene on the copper surface at different times. The domain size of the graphene is gradually increased when the growth times are extended. The maximum size of hexagonal graphene was found to be around 5.5 mm after 5 hours growth. In this process carbon diffusion continuously occurred on the large single-layer graphene, resulting in the formation of a second layer of graphene in certain regions. The carbon atoms in this layer were twisted due to weakened van der Waals interaction between graphene layers at high temperatures. The additional layers were successively grown in this region. The thus grown graphenes were transferred from Cu-foil to SiO2/Si substrate by electrochemical delamination method [1,2], and five layers stacked graphenes were confirmed by optical microscope (Figure 1a). Raman spectra and their map specify the quality and defect structure in the graphene lattice from the monolayer to twisted few-layer graphene (Figure 1b,c). As the number of twisted layers increases, a small D peak appears due to misalignment and localized strain [2]. We investigate the structural properties of twisted few layer graphene to advance research on high-quality graphene’s.
In detail, a Cu-foil was carefully annealed in Ar and H2 atmosphere to synthesize graphene to remove impurities and increase grain size. Then methane (CH4) was introduced at 1035 °C to grow high-quality graphene on the copper surface at different times. The domain size of the graphene is gradually increased when the growth times are extended. The maximum size of hexagonal graphene was found to be around 5.5 mm after 5 hours growth. In this process carbon diffusion continuously occurred on the large single-layer graphene, resulting in the formation of a second layer of graphene in certain regions. The carbon atoms in this layer were twisted due to weakened van der Waals interaction between graphene layers at high temperatures. The additional layers were successively grown in this region. The thus grown graphenes were transferred from Cu-foil to SiO2/Si substrate by electrochemical delamination method [1,2], and five layers stacked graphenes were confirmed by optical microscope (Figure 1a). Raman spectra and their map specify the quality and defect structure in the graphene lattice from the monolayer to twisted few-layer graphene (Figure 1b,c). As the number of twisted layers increases, a small D peak appears due to misalignment and localized strain [2]. We investigate the structural properties of twisted few layer graphene to advance research on high-quality graphene’s.