In2Si2S3X3 (X = S, Se, Te) Janus monolayers: from magnetic element-free spin-Hall transistor to sustainable energy generation

Abstract

Conventional spintronics uses ferromagnets for spin generation and detection; however, recent experiments have demonstrated highly efficient ferromagnet-free spin-Hall transistors. In this work, we propose a novel multiatomic direct band gap Janus In₂Si₂S₃Te₃ monolayer as a channel semiconductor that exhibits a finite spin-Hall conductivity with high charge carrier mobility of 2772 cm² V⁻¹ s⁻¹ at room temperature. In this model device, a pure spin current can be generated from the charge current using the spin-Hall effect whereas the inverse spin-Hall effect can be used to generate a Hall voltage. Further, this monolayer is predicted to possess a large out-of-plane piezoelectric coefficient of 160 pm V⁻¹ originating from crystal asymmetry and low elastic stiffness. A three-fold enhancement in solar to hydrogen efficiency is obtained for the Janus In₂Si₂S₃Se₃ monolayer (∼7.32%) compared to its pristine In₂Si₂S₆ monolayer (∼2.44%). Moreover, this work provides detailed theoretical insights into the emergent electronic and piezoelectric properties of multi-atomic In₂Si₂S₃X₃ (X = S, Se, Te) monolayers. Experimental synthesis of multi-atomic CuInP₂S₆ nanosheets paves the way for the exploration of the proposed semiconductors in spintronics, piezotronics, and water splitting.