Xia Jilin, Chen Fang, Li Jinghong, Tao Nongjian
Center for Bioelectronics and Biosensors, Biodesign Institute, Department of Electrical Engineering, Arizona State University, Tempe, AZ 85287, USA.
Nat Nanotechnol. 2009 Aug;4(8):505-9. doi: 10.1038/nnano.2009.177. Epub 2009 Jul 5.
Graphene has received widespread attention due to its unique electronic properties. Much of the research conducted so far has focused on electron mobility, which is determined by scattering from charged impurities and other inhomogeneities. However, another important quantity, the quantum capacitance, has been largely overlooked. Here, we report a direct measurement of the quantum capacitance of graphene as a function of gate potential using a three-electrode electrochemical configuration. The quantum capacitance has a non-zero minimum at the Dirac point and a linear increase on both sides of the minimum with relatively small slopes. Our findings -- which are not predicted by theory for ideal graphene -- suggest that charged impurities also influences the quantum capacitance. We also measured the capacitance in aqueous solutions at different ionic concentrations, and our results strongly indicate that the long-standing puzzle about the interfacial capacitance in carbon-based electrodes has a quantum origin.
石墨烯因其独特的电子特性而受到广泛关注。迄今为止进行的许多研究都集中在电子迁移率上，电子迁移率由带电杂质和其他不均匀性的散射决定。然而，另一个重要的量——量子电容，在很大程度上被忽视了。在这里，我们报告了使用三电极电化学配置对石墨烯量子电容作为栅极电位函数的直接测量。量子电容在狄拉克点处有一个非零最小值，并且在最小值两侧以相对较小的斜率线性增加。我们的发现——这是理想石墨烯理论所无法预测的——表明带电杂质也会影响量子电容。我们还测量了不同离子浓度的水溶液中的电容，我们的结果有力地表明，关于碳基电极界面电容的长期谜题有一个量子起源。
