Department of Physics, Purdue University, West Lafayette, IN 47907, USA.
Nanotechnology. 2011 Jul 22;22(29):295705. doi: 10.1088/0957-4484/22/29/295705. Epub 2011 Jun 16.
We have performed scanning gate microscopy (SGM) on graphene field effect transistors (GFET) using a biased metallic nanowire coated with a dielectric layer as a contact mode tip and local top gate. Electrical transport through graphene at various back gate voltages is monitored as a function of tip voltage and tip position. Near the Dirac point, the response of graphene resistance to the tip voltage shows significant variation with tip position, and SGM imaging displays mesoscopic domains of electron-doped and hole-doped regions. Our measurements reveal substantial spatial fluctuation in the carrier density in graphene due to extrinsic local doping from sources such as metal contacts, graphene edges, structural defects and resist residues. Our scanning gate measurements also demonstrate graphene's excellent capability to sense the local electric field and charges.
我们使用带有介电层的偏置金属纳米线作为接触模式探针和局部顶栅，对石墨烯场效应晶体管 (GFET) 进行了扫描栅显微镜 (SGM) 研究。通过不同背栅电压下的石墨烯进行电传输作为探针电压和探针位置的函数进行监测。在狄拉克点附近，石墨烯电阻对探针电压的响应随探针位置的显著变化，SGM 成像显示出电子掺杂和空穴掺杂区域的介观畴。我们的测量结果表明，由于金属接触、石墨烯边缘、结构缺陷和电阻残留物等外部局部掺杂，石墨烯中的载流子密度存在很大的空间波动。我们的扫描门测量还证明了石墨烯对局部电场和电荷的优异感应能力。
