Singh Anil Kumar, Gupta Anjan Kumar
Department of Physics, Indian Institute of Technology Kanpur, Kanpur 208016, India.
J Phys Condens Matter. 2017 Sep 27;29(38):385302. doi: 10.1088/1361-648X/aa7dbf. Epub 2017 Jul 5.
The electronic states at graphene-SiO interface and their inhomogeneity is investigated using the back-gate-voltage dependence of local tunnel spectra acquired with a scanning tunneling microscope. The conductance spectra show two, or occasionally three, minima that evolve along the bias-voltage axis with the back gate voltage. This evolution is modeled using tip-gating and interface states. The energy dependent interface states' density, [Formula: see text], required to model the back-gate evolution of the minima, is found to have significant inhomogeneity in its energy-width. A broad [Formula: see text] leads to an effect similar to a reduction in the Fermi velocity while the narrow [Formula: see text] leads to the pinning of the Fermi energy close to the Dirac point, as observed in some places, due to enhanced screening of the gate electric field by the narrow [Formula: see text]. Finally, this also demonstrates STM as a tool to probe the density of interface states in various 2D Dirac materials.
利用扫描隧道显微镜获取的局部隧道谱对背栅电压的依赖性，研究了石墨烯 - 二氧化硅界面处的电子态及其不均匀性。电导谱显示出两个，偶尔三个，随着背栅电压沿偏置电压轴演化的最小值。这种演化是通过针尖栅控和界面态进行建模的。为了对最小值的背栅演化进行建模所需的能量相关界面态密度[公式：见原文]，其能量宽度存在显著的不均匀性。宽的[公式：见原文]导致类似于费米速度降低的效应，而窄的[公式：见原文]由于窄的[公式：见原文]对栅极电场的增强屏蔽作用，导致费米能量在某些地方被钉扎在狄拉克点附近。最后，这也证明了扫描隧道显微镜是探测各种二维狄拉克材料中界面态密度的一种工具。
