Inelastic Scattering in Weak Localization for Single-Layer Graphene

Chemical-vapor-deposited graphene is used extensively to fabricate devices. However, the charge-neutral point (CNP) of this material appears at a relatively high back-gate voltage (VG) because of molecular adsorption and impurities on the graphene surface. In this study, a Ti-cleaning process is used to remove contaminants from the transferred graphene. Two contributions to the magnetoresistance are investigated: weak localization (WL) and inhomogeneous charge transport near the Dirac point. One of the most important parameters for clarifying the quantum transport properties is the inelastic scattering time. Fitting of the experimental results with a theoretical WL expression is performed to investigate the temperature and VG dependence of the inelastic scattering and intervalley scattering rates. Small momentum transfer due to Nyquist scattering is dominant in the CNP region, while large momentum transfer processes of direct electron-electron interaction dominate the electron and hole-transport regions.