Direct measurements of conductivity and mobility in millimeter-sized single-crystalline graphene via van der Pauw geometry

Ma Rui-Song^{1, 2, 3}, Huan Qing^{1, 2, 3}, Wu Liang-Mei^{1, 2, 3}, Yan Jia-Hao^{1, 2, 3}, Zhang Yu-Yang², Bao Li-Hong^{1, 2, 3, †}, Liu Yun-Qi⁴, Du Shi-Xuan^{1, 2, 3}, Gao Hong-Jun^{1, 2, 3, ‡}

(color online) Optical and STM characterization of graphene grown on Cu foil. (a): Optical photograph of graphene grown on Cu foil by CVD method. The scale bar is 1 cm and the grain size of the graphene grain is in the range of millimeter. (b): STM image showing one of the graphene-covered Cu foil. (c)–(d): Atomically-resolved STM images on the morphology in panel (b). Scanning conditions, (b)–(d): I_t = 367.3 pA and V_sample = 82.02 mV.