First-principles study of thermal transport properties in the two- and three-dimensional forms of Bi2O2Se

Recently, an air-stable layered semiconductor Bi2O2Se has been synthesized [Nat. Nanotechnol., 2017, 12, 530; Nano Lett. 2017, 17, 3021]. It possesses ultrahigh mobility, semiconductor properties, excellent environmental stability and easy accessibility. Here, we report on the thermal transport properties in monolayer (ML), bilayer (BL), and bulk forms of Bi2O2Se using density-functional theory and the Boltzmann transport approach. The results show that the ML exhibits better thermal transport properties than the BL and bulk. The intralayer opposite phonon vibrations greatly suppress the thermal transport and lead to an ultralow lattice thermal conductivity of B0.74 W m-1 K-1 in the ML, which has a large band gap of B2.12 eV, a low value of average acoustic group velocity of B0.76 km s-1, low-lying optical modes of B0.54 THz, strong optical-acoustic phonon coupling, and large Gruneisen parameters of B5.69. The size effect for all three forms is much less sensitive due to their short intrinsic phonon mean free path (MFP).