Electronic transport properties of hydrogenated and fluorinated graphene: a computational study

Hydrogenation and fluorination have been presented as two possible methods to open a bandgap in graphene, required for field-effect transistor applications. In this work, we present a detailed study of the phonon-limited mobility of electrons and holes in hydrogenated graphene (graphane) and fluorinated graphene (graphene fluoride). We pay special attention to the out-of-plane acoustic (ZA) phonons, responsible for the highest scattering rates in graphane and graphene fluoride. Considering the most adverse cut-off for long-wavelength ZA phonons, we have obtained electron (hole) mobilities of 28 (41) cm² V^-1 s^-1 for graphane and 96 (30) cm² V^-1 s^-1 for graphene fluoride. Nonetheless, for a more favorable cut-off wavelength of ∼2.6 nm, significantly higher electron (hole) mobilities of 233 (389) cm² V^-1 s^-1 for graphane and 460 (105) cm² V^-1 s^-1 for graphene fluoride are achieved. Moreover, while complete suppression of ZA phonons can increase the electron (hole) mobility in graphane up to 278 (391) cm² V^-1 s^-1, it does not affect the carrier mobilities in graphene fluoride. Velocity-field characteristics reveal that the electron velocity in graphane saturates at an electric field of ∼4 × 10⁵ V cm^-1. Comparing the mobilities with other two-dimensional (2D) semiconductors, we find that hydrogenation and fluorination are two promising avenues to realize a 2D semiconductor while providing good carrier mobilities.