Ni Zhen Hua, Yu Ting, Luo Zhi Qiang, Wang Ying Ying, Liu Lei, Wong Choun Pei, Miao Jianmin, Huang Wei, Shen Ze Xiang
Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore.
ACS Nano. 2009 Mar 24;3(3):569-74. doi: 10.1021/nn900130g.
Charged impurity (CI) scattering is one of the dominant factors that affects the carrier mobility in graphene. In this paper, we use Raman spectroscopy to probe the charged impurities in suspended graphene. We find that the 2D band intensity is very sensitive to the CI concentration in graphene, while the G band intensity is not affected. The intensity ratio between the 2D and G bands, I(2D)/I(G), of suspended graphene is much stronger compared to that of nonsuspended graphene, due to the extremely low CI concentration in the former. This finding is consistent with the ultrahigh carrier mobility in suspended graphene observed in recent transport measurements. Our results also suggest that at low CI concentrations that are critical for device applications, the I(2D)/I(G) ratio is a better criterion in selecting high quality single layer graphene samples than is the G band blue shift.
带电杂质（CI）散射是影响石墨烯中载流子迁移率的主要因素之一。在本文中，我们使用拉曼光谱来探测悬浮石墨烯中的带电杂质。我们发现，二维带强度对石墨烯中的CI浓度非常敏感，而G带强度不受影响。由于前者的CI浓度极低，悬浮石墨烯的二维带与G带强度比I(2D)/I(G)比非悬浮石墨烯要强得多。这一发现与最近在输运测量中观察到的悬浮石墨烯中的超高载流子迁移率一致。我们的结果还表明，在对器件应用至关重要的低CI浓度下，I(2D)/I(G)比在选择高质量单层石墨烯样品方面比G带蓝移是更好的标准。
