The origin of instinct charge transport for Dirac carbon sheet materials: Roles of acetylenic linkage and electron-phonon couplings
Within the past few years, the intriguing Dirac cones in graphene have attracted intense interest in the 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) are investigated using the Boltzmann transport equation within first-principles framework considering electron-phonon coupling (EPC). Despite the three compounds investigated are all 2D Dirac carbon materials, they demonstrate distinctly different carrier mobilities by one order of magnitude (2.2×10^4 cm^2/Vs for α-GY, 2.1×10^3 cm^2/Vs for α-GDY and 1.9×10^3 cm^2/Vs for β-GY at room-temperature and carrier connection n ~ 3×10^12 /cm^2). Acetylenic linkage limited group velocity and E2g phonon modes limited scattering time are the origins of the essential difference of mobility in these materials. For example, few and uniformly equivalent acetylenic linkages as well as few number of E2g phonon modes tend to obtain high mobilities. A simple relation of mobility determined by the number of E2g modes has been concluded, which may enable a quick estimation of the mobilities for Dirac materials by the number of E2g phonon modes. α-GY is identified as a promising alternative to graphene in next generation nanoelectronic devices.