A non-contact graphene surface scattering rate characterization method at microwave frequency by combining Raman spectroscopy and coaxial connectors measurement Xing-Chang Wei a,b , Yi-Li Xu a , Nan Meng a,c , Yang Xu a,b,c, * , Ayaz Hakro a,c , Gao-Le Dai a , Ran Hao a , Er-Ping Li a,b, * a Department of Information Science and Electronic Engineering, Zhejiang University, Hangzhou 310027, China b Cyber Innovation Joint Research Center, Zhejiang University, Hangzhou 310027, China c Cyrus Tang Center for Sensor Materials and Applications, Zhejiang University, Hangzhou 310027, China ARTICLE INFO Article history: Received 26 December 2013 Accepted 30 April 2014 Available online 10 May 2014 ABSTRACT A non-contact method is proposed to characterize graphene at microwave frequency by combining Raman spectroscopy and Amphenol Precision Connector (APC-7). The CVD- grown graphene is transferred to the ring-shape Teflon substrate and characterized by Raman spectroscopy to estimate its doping density and the related Fermi energy. The graphene is then sandwiched between two APC-7 coaxial connectors and S parameters under transverse electromagnetic (TEM) mode normal incident waves are measured to extract the surface conductivity through transmission matrix, in which the de-embedding process can be avoided. By combing the Kubo formula with our proposed circuit model, the scattering rate of graphene on Teflon substrate is obtained and analyzed. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction Graphene is a single layer of carbon atoms arranged in a hon- eycomb lattice and can be viewed as the fundamental block of other graphitic carbon allotropes [1–3]. Graphene has extraor- dinary mechanical properties [4,5], superior carrier mobility [6,7], and high thermal conductivity [8]. The extraordinary properties and freelance hybridization with other materials make graphene one of the most promising candidates for the future applications in electronic [9–13] and optic engineer- ing [14–17]. To date, various synthesis techniques of graphene are proposed, such as mechanical exfoliation, chemical vapor deposition (CVD) and SiC epitaxial growth. Property of graph- ene synthesized from different techniques varies tremen- dously. However, the performance of graphene-based device is strongly dependent on the properties of graphene layer itself, characterization of graphene without deteriorating is of ultimate importance. Developing a rapid, simple, and reli- able technique to characterize the basic electronic properties of graphene is emergently required. To determine the scattering rate of graphene at microwave frequency is usually through I-V measurement, which will perturb or even deteriorate the intrinsic properties of graph- ene under test [18,19]. Coplanar waveguide (CPW) structure, http://dx.doi.org/10.1016/j.carbon.2014.04.095 0008-6223/Ó 2014 Elsevier Ltd. All rights reserved. * Corresponding authors. Address: Department of Information Science and Electronic Engineering, Zhejiang University, Hangzhou 310027, China. E-mail addresses: yangxu-isee@zju.edu.cn (Y. Xu), liep@zju.edu.cn (E.-P. Li). CARBON 77 (2014) 53 – 58 Available at www.sciencedirect.com ScienceDirect journal homepage: www.elsevier.com/locate/carbon