Size, orientation, and boundary of graphene domains are the current focus of chemical vapor deposition (CVD) growth because they are closely related to graphene’s physical properties. Here, we study the domain structure of single-layer graphene grown by ambient pressure CVD over heteroepitaxial Cu(111) and Cu(100) films. Low energy electron microscope measurements reveal that the Cu(111) film gives uniform single-layer graphene whose orientation is consistent with the underlying Cu lattice for areas over 1 mm2. On the other hand, single-layer graphene grown on Cu(100) film exhibits clear multidomain structure with two main orientations rotated by 30°. Moreover, a weak Raman D-band is observed along the domain boundaries for the graphene grown on the Cu(100). Our results give new insights into the growth mechanism of CVD-grown graphene over Cu metals and offer a new direction for the realization of single-crystalline graphene.

Epitaxial chemical vapor deposition (CVD) growth of uniform single-layer graphene is demonstrated over Co film crystallized on c-plane sapphire. The single crystalline Co film is realized on the sapphire substrate by optimized high-temperature sputtering and successive H(2) annealing. This crystalline Co film enables the formation of uniform single-layer graphene, while a polycrystalline Co film deposited on a SiO(2)/Si substrate gives a number of graphene flakes with various thicknesses. Moreover, an epitaxial relationship between the as-grown graphene and Co lattice is observed when synthesis occurs at 1000 °C; the direction of the hexagonal lattice of the single-layer graphene completely matches with that of the underneath Co/sapphire substrate. The orientation of graphene depends on the growth temperature and, at 900 °C, the graphene lattice is rotated at 22 ± 8° with respect to the Co lattice direction. Our work expands a possibility of synthesizing single-layer graphene over various metal catalysts. Moreover, our CVD growth gives a graphene film with predefined orientation, and thus can be applied to graphene engineering, such as cutting along a specific crystallographic direction, for future electronics applications.

We report the atmospheric pressure chemical vapor deposition (CVD) growth of single-layer graphene over a crystalline Cu(111) film heteroepitaxially deposited on c-plane sapphire. Orientation-controlled, epitaxial single-layer graphene is achieved over the Cu(111) film on sapphire, while a polycrystalline Cu film deposited on a Si wafer gives non-uniform graphene with multi-layer flakes. Moreover, the CVD temperature is found to affect the quality and orientation of graphene grown on the Cu/sapphire substrates. The CVD growth at 1000 ºC gives high-quality epitaxial single-layer graphene whose orientation of hexagonal lattice matches with the Cu(111) lattice which is determined by the sapphire's crystallographic direction. At lower CVD temperature of 900 ºC, low-quality graphene with

For electronic applications, synthesis of large-area, single-layer graphene with high crystallinity is required. One of the most promising and widely employed methods is chemical vapor deposition (CVD) using Cu foil/film as the catalyst. However, the CVD graphene is generally polycrystalline and contains a significant amount of domain boundaries that limit intrinsic physical properties of graphene. In this Perspective, we discuss the growth mechanism of graphene on a Cu catalyst and review recent development in the observation and control of the domain structure of graphene. We emphasize the importance of the growth condition and crystallinity of the Cu catalyst for the realization of large-area, single-crystalline graphene.

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