Tuning transport performance in two-dimensional metal-organic framework semiconductors: Role of the metal d band

Abstract

Hybrid metal-organic frameworks have some exotic electronic properties, such as extremely high electron and hole mobilities and nontrivial topological properties. Here, we systematically study the electronic properties of the two-dimensional metal-organic framework semiconductors (MOFSs) (M3S6C6, M = Mg, Ca, Zn, Cd, Ge, and Sn) using the first principles calculations. We find that the metal d band is important in determining the hole transport properties of M3S6C6. The p-d hybridization between the metal d and S-C p bands will delocalize the wavefunction of the band edge states and reduce the effective mass. From group IIA (Mg, Ca) to IVA (Ge, Sn) to IIB (Zn, Cd), as the p-d coupling increases, the hole effective masses dramatically decrease. Additionally, due to the fact that the conduction band minimum of group IIB (Zn, Cd) MOFSs is mainly dominated by the delocalized M s state, they also have the very small electron effective mass. Therefore, the 2D group IIB (Zn, Cd) MOFSs have excellent hole and electron effective masses, which are comparable with the conventional semiconductors and even better than the popular 2D materials WS2 and MoS2. This result suggests that Zn3S6C6 and Cd3S6C6 MOFSs could be the promising 2D semiconductors for the electronic applications.