Characterizing the low doping regime and charge fluctuation in graphene using Raman spectroscopy.*

Graphene without charge impurities is essential for high-quality transport-based devices. Here we propose using Raman spectroscopy, as opposed to labor-intensive transport measurements, to monitor low-level accidental doping and charge fluctuation in graphene. At low doping level, monitoring the 2D band splitting reveals a whole host of information on charge density screening in graphene [1]. This method provides orders of magnitude higher precision than the reported results using the G-band shift. Our work provides a simple, noninvasive way to explore doping levels and charge fluctuation in graphene, which is important to evaluate the quality of graphene before fabricating graphene-based devices.

[1] Wang, X., Christopher, J.W. and Swan, A.K., 2017. 2D Raman band splitting in graphene: Charge screening and lifting of the K-point Kohn anomaly. Scientific Reports, 7(1), p.13539.