Weak localization scattering lengths in epitaxial, and CVD graphene

Weak localization in graphene is studied as a function of carrier density in the range from 1×10¹¹ cm^-2 to 1.43×10¹³ cm^-2 using devices produced by epitaxial growth onto SiC and CVD growth on thin metal film. The magnetic field dependent weak localization is found to be well fitted by theory, which is then used to analyze the dependence of the scattering lengths L_φ, Lᵢ, and L* on carrier density. We find no significant carrier dependence for L_φ, a weak decrease for Lᵢ with increasing carrier density just beyond a large standard error, and a n^-1/4 dependence for L*. We demonstrate that currents as low as 0.01 nA are required in smaller devices to avoid hot-electron artifacts in measurements of the quantum corrections to conductivity.