Structural Instability of Transferred Graphene Grown by Chemical Vapor Deposition against Heating

A heating treatment is often used in graphene research to remove adsorbates and resist materials from graphene. Heating graphene followed by air exposure is also known to result in heavy hole doping in graphene, although the role of heating has been unclear. Here, we demonstrate that a practical graphene sample fabricated using the commonly used growth and transfer techniques is unstable against heating in a high vacuum. Structural disorder likely due to defect formation is induced by heating, and the disorder is accompanied by hole doping. Our analysis shows that the main cause of the defect formation is graphene reacting with O₂ and H₂O molecules inserted between graphene and the substrate. The hole doping caused by air exposure after heating is explained by gas adsorption at the defect sites

Domain Structure and Boundary in Single-Layer Graphene Grown on Cu(111) and Cu(100) Films

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