Phonon and electron transport in Janus monolayers based on InSe

We systematically investigated the phonon and electron transport properties of monolayer InSe and its Janus derivatives including monolayer Inalt;subagt;2alt;/subagt;SSe and Inalt;subagt;2alt;/subagt;SeTe by first-principles calculations. The breaking of mirror symmetry produces a distinguishable Aalt;subagt;1alt;/subagt; peak in the Raman spectra of monolayer Inalt;subagt;2alt;/subagt;SSe and Inalt;subagt;2alt;/subagt;SeTe. The long-range harmonic and anharmonic interactions play an important role in the heat transport of the group-III chalcogenides. The room-temperature thermal conductivity (?) of monolayer InSe, Inalt;subagt;2alt;/subagt;SSe and Inalt;subagt;2alt;/subagt;SeTe is 44.6, 46.9, and 29.9 W/(mK), respectively. There is a competition effect between atomic mass, phonon group velocity and phonon lifetime. The ? can be further effectively modulated by sample size for the purpose of thermoelectric applications. Meanwhile, monolayer Inalt;subagt;2alt;/subagt;SeTe exhibits a direct band gap of 1.8 eV and higher electron mobility than that of monolayer InSe, due to the smaller electron effective mass caused by tensile strain on the Se side and smaller deformation potential. These results indicate that 2D Janus group-III chalcogenides can provide a platform to design the new electronic, optoelectronic and thermoelectric devices.