学术文献库

Germanium selenide (GeSe) is a unique two-dimensional (2D) material showing various polymorphs stable at ambient condition. Recently, a new phase with a layered hexagonal lattice (γ-GeSe) was synthesized with ambient stability and extraordinary electronic conductivity even higher than graphite while its monolayer is semiconducting. In this work, via using first-principles derived force constants and Boltzmann transport theory we explore the lattice thermal conductivity (κ_l) of the monolayer γ-GeSe, together with a comparison with monolayer α-GeSe and β-GeSe. The κ_l of γ-phase is relatively low (5.50 W/mK), comparable with those of α- and β- phases. The acoustic branches in α-GeSe are well separated from the optical branches, limiting scattering channels in the phase space, while for \b{eta}-GeSe and γ-GeSe the acoustic branches are resonant with the low-frequency optical branches facilitating more phonon-phonon scattering. For γ-GeSe, the cumulative κ_l is isotropic and phononic representative mean free path (rMFP) is the shortest (17.07 nm) amongst the three polymorphs, indicating that the κ_l of the γ phase is less likely to be affected by the size of the sample, while for α-GeSe the cumulative κ_l grows slowly with mean free path and the rMFP is longer (up to 20.56 and 35.94 nm along zigzag and armchair direction, respectively), showing a stronger size-dependence of κ_l. Our work suggests that GeSe polymorphs with overall low thermal conductivity are promising contenders for thermoelectric and thermal management applications.