The origin of intrinsic charge transport for Dirac carbon sheet materials: Roles of acetylenic linkage and electron-phonon couplings

Within the past few years, intriguing graphene Dirac cones have attracted intense interest in novel two-dimensional (2D) Dirac materials as ultrahigh-mobility functional materials. In this work, the phonon-limited charge transport properties of α-graphyne (α-GY), α-graphdiyne (α-GDY), and β-graphyne (β-GY) were investigated using the Boltzmann transport equation within the first-principles framework while considering the electron-phonon coupling (EPC). Despite all three investigated compounds being 2D Dirac carbon materials, each demonstrated distinctly different carrier mobilities by one order of magnitude (2.2 × 10⁴ cm² V^-1 s^-1 for α-GY, 2.1 × 10³ cm² V^-1 s^-1 for α-GDY and 1.9 × 10³ cm² V^-1 s^-1 for β-GY at room-temperature and a carrier connection of n ∼ 3 × 10¹² cm^-2). The essential differences in the mobilities of these materials originated from the acetylenic linkage limiting the group velocity and the E_2g phonon modes limiting the scattering time. For example, a few uniformly equivalent acetylenic linkages and E_2g phonon modes tend to generate high mobilities. A simple mobility relationship was determined using the number of E_2g photon modes, allowing for a quick estimation of the mobilities for Dirac materials. α-GY was identified as a promising alternative to graphene for next generation nanoelectronic devices.