Center for Nanophysics and Advanced Materials, University of Maryland, College Park, Maryland 20742-4111, United States.
Nano Lett. 2013 Aug 14;13(8):3576-80. doi: 10.1021/nl4012529. Epub 2013 Aug 1.
Kelvin probe microscopy in ultrahigh vacuum is used to image the local electrostatic potential fluctuations above hexagonal boron nitride (h-BN) and SiO2, common substrates for graphene. Results are compared to a model of randomly distributed charges in a two-dimensional (2D) plane. For SiO2, the results are well modeled by 2D charge densities ranging from 0.24 to 2.7 × 10(11) cm(-2), while h-BN displays potential fluctuations 1-2 orders of magnitude lower than SiO2, consistent with the improvement in charge carrier mobility for graphene on h-BN compared to SiO2. Electron beam exposure of SiO2 increases the charge density fluctuations, creating long-lived metastable charge populations of ~2 × 10(11) cm(-2) at room temperature, which can be reversed by heating.
在超高真空环境下，利用 Kelvin 探针显微镜对六方氮化硼（h-BN）和二氧化硅（SiO2）这两种常见的石墨烯衬底上方的局部静电电势波动进行成像。结果与二维（2D）平面中随机分布电荷的模型进行了对比。对于 SiO2，实验结果可以通过 2D 电荷密度为 0.24 到 2.7×10(11) cm(-2) 的模型很好地拟合，而 h-BN 显示出的电势波动比 SiO2 低 1-2 个数量级，这与 h-BN 上石墨烯的电荷载流子迁移率相对于 SiO2 的提高一致。电子束辐照 SiO2 会增加电荷密度波动，在室温下产生寿命较长的亚稳电荷群体，约为 2×10(11) cm(-2)，通过加热可以使其反转。
