Imaging of Photocurrent Generation and Collection in Single-Layer Graphene
Imaging of Photocurrent Generation and Collection in Single-Layer Graphene
复制标题
DOI：
10.1021/nl8029493
复制
发表时间：
2009-05-01
期刊：
影响因子：
10.8
通讯作者：
Ruiz-Vargas, Carlos
中科院分区：
文献类型：
--
作者：
Park, Jiwoong;Ahn, Y. H.;Ruiz-Vargas, Carlos
与线性纳米结构不同，单层石墨烯(SLG)中产生的光电流有望表现出二维特性。这使得能够研究与几个空间变化因素(例如光电流产生和收集的位置)以及SLG的整体电子能带配置相关的载流子动力学。在这封信中，我们使用扫描光电流显微镜来研究多电极几何结构中SLG中光电流产生和收集的空间映射。金属-石墨烯接触附近的强电场导致高效的光电流产生，导致>；30%的电子-空穴分离效率。用接触光电流的极性和大小研究了接触附近的能带排列和石墨烯电势，结果表明石墨烯电势存在较大的空间变化。我们用多电极器件结构进行的测量表明，光电流在不同的收集极之间具有明显的方向依赖性。在相同的测量方案中，我们还通过成像激光感应加热电极产生的热电流来确定不同栅极条件下石墨烯中的主要载流子。
Unlike in linear nanostructures, photocurrent generated in single-layer graphene (SLG) is expected to display two-dimensional characteristics. This allows the investigation of carrier dynamics, in relation to several spatially varying factors (such as the location of photocurrent generation and collection) and the overall electron band configuration of the SLG. In this letter, we use scanning photocurrent microscopy to investigate the spatial mapping of photocurrent generation and collection in SLG in a multielectrode geometry. A strong electric field near metal-graphene contacts leads to efficient photocurrent generation, resulting in > 30% efficiency for electron-hole separation. The polarity and magnitude of contact photocurrent are used to study the band alignment and graphene electrical potential near contacts, from which it is shown that there exist large-scale spatial variations in graphene electric potential. Our measurements with a multielectrode device configuration reveal that photocurrent is distributed with a clear directional dependence among different collector electrodes. In the same measurement scheme, we also determine the majority carrier in graphene under different gate conditions by imaging the thermocurrent generated by laser-induced heating of electrodes.