Ultrahigh electron mobility in one-dimensional single-chain Bi4RuX2 (X = I, Br)

Low dimensional materials usually bring about unique physical properties and exceptional phenomena. Beyond the highly sought-after two-dimensional materials, the quasi-one-dimensional (1D) materials have attracted increasing attention due to the further reduced dimensionality and the resultant more pronounced quantum confinement effect. In the present Letter, we systematically explore the stability, mechanical properties, electronic structure, and optical properties of the 1D single-chain ternary bismuth subhalides Bi4RuX2 (X = I, Br) by first-principles calculations. 1D Bi4RuX2 exhibit good dynamical, thermal, and mechanical stability. Along with the dimensionality reduction from three-dimensional bulk to 1D single-chain, Bi4RuX2 undergo a transition from the indirect bandgap semiconductor to direct bandgap semiconductor, and their bandgap values increase from 1.028 and 1.151 eV to 1.224 and 1.263 eV, respectively. More importantly, 1D Bi4RuI2 and Bi4RuBr2 possess very high electron mobilities of 416.25 and 277.17 cm2 V−1 s−1, which far outperform the hole mobilities of 0.95 and 1.35 cm2 V−1 s−1. In addition, the bandgap values and band edge positions can be effectively modulated by the tensile strains, which meet the conditions for photocatalytic water splitting during a wide strain range. Furthermore, the 1D Bi4RuX2 exhibit an excellent light absorption ability of ∼105 cm−1, which can be regulated by the tensile strain for the highly efficient utilization of solar energy. The excellent electronic and optical properties indicate 1D Bi4RuX2 are promising materials for potential applications in high-performance nanoelectronic, optoelectronic devices, photocatalytic water splitting, and solar energy conversion.