Current research efforts are aimed at controlling the electronic properties via doping graphene. Previously, dopant-induced changes in the Fermi velocity were observed to result in an effectively downshifted Raman peak below the G′-band for n-doped carbon nanotubes. However, in the case of N-doped graphene, we find that several Raman features vary depending upon both dopant concentration and its bonding environment. For instance, only pyridinic/pyrrolic dopants were observed to result in intense D/D′-bands with a concomitant downshift in the G′-band. Here, we correlate x-ray photoelectron measurements with Raman spectra to elucidate effects of dopant bonding configuration on vibrational properties of graphene.

We explore the effects of crystallite size (L(a)) on the linear and non-linear optical properties of chemical vapor deposition grown polycrystalline graphene. The π-plasmon resonance present at ∼4.75 eV (∼260 nm) in the optical absorption spectrum of graphene follows the empirical relationship λ(π) = 250.5 nm + 89.5 nm(2)/L(a), where λ(π) represents the π-plasmon wavelength. Furthermore, our Z-scan studies reveal that the crystallite size significantly changes the saturation intensity in CVD grown graphene. Notably, in comparison to epitaxial graphene layers grown on SiC wafers which exhibit a photogenerated carrier lifetime of few picoseconds, we find that the photogenerated carriers in our CVD grown graphene can exhibit lifetimes as long as nanoseconds.