Gate-controlled ionization and screening of cobalt adatoms on a graphene surface
Gate-controlled ionization and screening of cobalt adatoms on a graphene surface
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DOI：
10.1038/nphys1807
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发表时间：
2011-01-01
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：
Brar, Victor W.;Decker, Regis;Crommie, Michael F.
石墨烯杂质提供了迁移率限制无序的来源和期望地改变石墨烯电子结构的手段。石墨烯上的吸附物可以，例如，诱导库仑散射（1，2），改变电子-声子相互作用（3），移动化学势（1，2），改变有效介电常数（4），并在诸如“石墨烯”的情况下（5）-形成全新的二维材料。虽然这些效应迄今为止主要是用空间平均技术研究的，但要理解这种行为的微观物理学，需要对石墨烯上杂质的亚纳米级电子和结构特性进行局部探测。在这里，我们描述了扫描隧道显微镜和光谱测量单个钴原子沉积到背栅石墨烯器件。我们发现，钴吸附原子的电子结构可以通过施加器件的栅极电压进行调谐，并且钴原子可以被可逆地电离。观察到以这种方式电离的Co吸附原子周围形成大的屏蔽云，并且我们观察到一些固有的石墨烯缺陷也显示出充电行为。我们的研究结果提供了新的见解带电杂质散射在石墨烯，以及使用石墨烯设备作为化学传感器的可能性。
Graphene impurities provide both a source of mobility-limiting disorder and a means to desirably alter graphene electronic structure. Adsorbates on graphene can, for example, induce Coulomb scattering(1,2), alter electron-phonon interactions(3), shift the chemical potential(1,2), change the effective dielectric constant(4) and-in cases such as 'graphane'(5)-form whole new two-dimensional materials. While these effects have thus far been primarily studied with spatially averaged techniques, understanding the microscopic physics of such behaviour requires local-probe exploration of the subnanometre-scale electronic and structural properties of impurities on graphene. Here we describe scanning tunnelling microscopy and spectroscopy measurements made on individual Co atoms deposited onto back-gated graphene devices. We find that the electronic structure of Co adatoms can be tuned by application of the device gate voltage, and that the Co atoms can be reversibly ionized. Large screening clouds are observed to form around Co adatoms ionized in this way, and we observe that some intrinsic graphene defects also show charging behaviour. Our results provide new insight into charged-impurity scattering in graphene, as well as the possibility of using graphene devices as chemical sensors.