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 In₂SSe and In₂SeTe by first-principles calculations. The breaking of mirror symmetry produces a distinguishable A ₁ peak in the Raman spectra of monolayer In₂SSe and In₂SeTe. 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 ([Formula: see text]) of monolayer InSe, In₂SSe and In₂SeTe are 44.6, 46.9, and 29.9 W (mK)^-1, respectively. There is a competition effect between atomic mass, phonon group velocity and phonon lifetime. The [Formula: see text] can be further effectively modulated by sample size for the purpose of thermoelectric applications. Meanwhile, monolayer In₂SeTe exhibits a direct band gap of 1.8 eV and a 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.