Microwave microscopy of few-layer graphene

Graphene has emerged as a promising material for high speed nano-electronics applications due to the relatively high carrier mobility that can be achieved. To further investigate electronic transport in graphene and reveal its potential for microwave applications [1], a near-field scanning microwave microscope with the probe formed by an electrically open end of a 4 GHz half-lambda parallel-strip transmission line resonator has been employed [2]. We find that the microwave response of mono- and few-layer graphene flakes is determined by the local sheet impedance, which is found to be predominantly active. From fitting a quantitative electrodynamic model (relating the probe resonant frequency shift to 2D conductivity of single- and few-layer graphene) to the experimental data we evaluate graphene sheet resistance as a function of thickness. Near-field scanning microwave microscopy can simultaneously image location, geometry, thickness, and distribution of electrical properties of graphene without a need for device fabrication. \\[4pt] [1] W. Kundhikanjana, K. Lai, H. Wang, H. Dai, M. A. Kelly, and Z.-X. Shen, \textit{Nano Lett.} \textbf{9}, 3762 (2009); Y.-M. Lin, C. Dimitrakopoulos, K. A. Jenkins, D. B. Farmer, H.-Y. Chiu, A. Grill, and Ph. Avouris, Science \textbf{327}, 662 (2010). \\[0pt] [2] V. V. Talanov, C. Del Barga, L. Wickey, I. Kalichava, E. Gonzales, E. A. Shaner, A.V. Gin, and N. G. Kalugin, ASC Nano \textbf{4} (7), 3831(2010).