Direct measurements of conductivity and mobility in millimeter-sized single-crystalline graphene via van der Pauw geometry
Ma Rui-Song1, 2, 3, Huan Qing1, 2, 3, Wu Liang-Mei1, 2, 3, Yan Jia-Hao1, 2, 3, Zhang Yu-Yang2, Bao Li-Hong1, 2, 3, †, Liu Yun-Qi4, Du Shi-Xuan1, 2, 3, Gao Hong-Jun1, 2, 3, ‡
       

(color online) Local transport properties of the millimeter-sized graphene flake. (a): Plot of conductivities versus gate voltage, measured near the edge of the graphene flake. The inset micrograph shows the positions of the four probes during measurements. The extracted hole and electron mobility are 4460.1±103.0 cm2·V−1·s−1 and 5384.3±327.7 cm2·V−1·s−1, respectively. The Dirac voltage is at 0 V, indicating the high quality of single crystalline graphene flake. (b): Variation of conductivities with gate voltage, measured in the middle of the graphene flake near the multi-layer graphene islands. The inset show the micrograph during four-probe measurements. The extracted hole and electron mobility are 1944.8±152.8 cm2·V−1·s−1 and 2584.4±115.5 cm2·V−1·s−1, respectively. The Dirac voltage is located at −20 V.