Excitation-driven non-thermal conversion of few-layer graphenes into sp3-bonded carbon nanofilms

Abstract

The microscopic effect of electronic excitations on the transformation of few-layer graphene into sp3-bonded carbon nanofilm is examined through static and real-time propagation time-dependent density-functional theory. Statically, the presence of holes in high-lying valence bands is shown to reduce the energy barrier substantially. Dynamics of excited state electrons combined with Ehrenfest atomic motions reveals that non-thermal fast transformation from sp2 to sp3 can happen within a few hundreds femtoseconds. We suggest that once the efficient path of sp3 carbon surface passivation is provided, the excitation from π to π∗ bands of few-layer graphenes can be utilized to achieve the transformation into nanoscale sp3-bonded carbon film without heating process.