title: Probing charged impurities in suspended graphene using Raman spectroscopy.
abstract: 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.
authors.affiliation: Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore.
authors.forename: Zhen Hua
authors.initials: ZH
authors.lastname: Ni
authors.forename: Ting
authors.initials: T
authors.lastname: Yu
authors.forename: Zhi Qiang
authors.initials: ZQ
authors.lastname: Luo
authors.forename: Ying Ying
authors.initials: YY
authors.lastname: Wang
authors.forename: Lei
authors.initials: L
authors.lastname: Liu
authors.forename: Choun Pei
authors.initials: CP
authors.lastname: Wong
authors.forename: Jianmin
authors.initials: J
authors.lastname: Miao
authors.forename: Wei
authors.initials: W
authors.lastname: Huang
authors.forename: Ze Xiang
authors.initials: ZX
authors.lastname: Shen