Direct Imaging of Charged Impurity Density in Common Graphene Substrates

作者：Burson Kristen M; Cullen William G^*; Adam Shaffique; Dean Cory R; Watanabe K; Taniguchi T; Kim Philip; Fuhrer Michael S

来源：Nano Letters, 2013, 13(8): 3576-3580.

DOI：10.1021/nl4012529

• Graphene
• noncontact atomic force microscopy
• Kelvin probe force microscopy
• charged impurity scattering
• charge inhomogeneity

Kelvin probe microscopy in ultrahigh vacuum is used to image the local electrostatic potential fluctuations above hexagonal boron nitride (h-BN) and SiO2, common substrates for graphene. Results are compared to a model of randomly distributed charges in a two-dimensional (2D) plane. For SiO2, the results are well modeled by 2D charge densities ranging from 0.24 to 2.7 X 10(11) cm(-2), while h-BN displays potential fluctuations 1-2 orders of magnitude lower than SiO2, consistent with the improvement in charge carrier mobility for graphene on h-BN compared to SiO2. Electron beam exposure of SiO2 increases the charge density fluctuations, creating long-lived metastable charge populations of similar to 2 x 10(11) cm(-2) at room temperature, which can be reversed by heating.

• 出版日期2013-8