Photoexfoliation of graphene from graphite: an ab initio study.

We propose to use ultrashort laser pulses to detach intact graphene monolayers from a graphite surface, one at a time. As suggested by a combination of real-time ab initio time-dependent density functional calculations for electrons with molecular dynamics simulations for ions, this athermal exfoliation process follows exposure to femtosecond laser pulses with a wavelength of 800 nm and the full width at half maximum (FWHM) of 45 fs. Shorter pulses (FWHM=10  fs) with the same wavelength and intensity speed up the exfoliation and cause transient contraction in subsurface layers. Photoexfoliation should be capable of producing intact graphene monolayers free of contaminants and defects at a high rate.