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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 x $10^{11}$\,cm$^{-2}$ to 1.43 x $10^{13}$\,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 analyse the dependence of the scattering lengths L$_φ$, L$_i$, and L$_*$ on carrier density. We find no significant carrier dependence for L$_φ$, a weak decrease for L$_i$ with increasing carrier density just beyond a large standard error, and a n$^{-\frac{1}{4}}$ dependence for L$_*$. We demonstrate that currents as low as 0.01\,nA are required in smaller devices to avoid hot-electron artefacts in measurements of the quantum corrections to conductivity.