Origin of spatial charge inhomogeneity in graphene
Origin of spatial charge inhomogeneity in graphene
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DOI：
10.1038/nphys1365
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发表时间：
2009-10-01
期刊：
影响因子：
19.6
通讯作者：
Crommie, Michael F.
中科院分区：
文献类型：
--
作者：
Zhang, Yuanbo;Brar, Victor W.;Crommie, Michael F.
在理想的石墨烯片中，电荷载流子表现为二维狄拉克费米子（1）。这已经被放置在SiO2衬底上的石墨烯薄片中的半整数量子霍尔效应的发现所证实。然而，石墨烯中的狄拉克费米子会受到微观扰动，包括地形波纹和电子密度不均匀性（即电荷池）。这种扰动深刻地改变了狄拉克-费米子的行为，对它们的基础物理和未来的石墨烯器件应用产生了影响。在这里，我们报告了一种新的技术的Dirac点映射，我们已经用来确定在石墨烯中的电荷不均匀性的起源。我们发现石墨烯电荷密度的波动不是由拓扑波纹引起的，而是由石墨烯下方的电荷捐赠杂质引起的。这些杂质诱导令人惊讶的驻波图案由于意外的背散射狄拉克费米子。这种波型可以通过电选通连续调制。我们的观察提供了新的见解狄拉克费米子的杂质散射和限制电子迁移率在石墨烯的微观机制。
In an ideal graphene sheet, charge carriers behave as two-dimensional Dirac fermions(1). This has been confirmed by the discovery of a half-integer quantum Hall effect in graphene flakes placed on a SiO2 substrate. The Dirac fermions in graphene, however, are subject to microscopic perturbations that include topographic corrugations and electron-density inhomogeneities (that is, charge puddles). Such perturbations profoundly alter Dirac-fermion behaviour, with implications for their fundamental physics as well as for future graphene device applications. Here we report a new technique of Dirac-point mapping that we have used to determine the origin of charge inhomogeneities in graphene. We find that fluctuations in graphene charge density are caused not by topographical corrugations, but rather by charge-donating impurities below the graphene. These impurities induce surprising standing wave patterns due to unexpected backscattering of Dirac fermions. Such wave patterns can be continuously modulated by electric gating. Our observations provide new insight into impurity scattering of Dirac fermions and the microscopic mechanisms limiting electronic mobility in graphene.