Widely tunable and anisotropic charge carrier mobility in monolayer tin(II) selenide using biaxial strain: a first-principles study

Two dimensional (2D) materials are promising candidates for developing next-generation electronics. Monolayer tin(II) selenide (SnSe), which can be obtained by exfoliating bulk SnSe crystals at a low cleavage energy, is shown to be a nearly direct band gap semiconductor using first-principles calculations. By incorporating the anisotropic characteristics of effective masses, elastic modulus, and deformation potential with the longitudinal acoustic deformation potential scattering mechanism, we demonstrate that the charge carrier mobilities of monolayer SnSe strongly depend on the carrier type, valley index, transport direction, and biaxial strain. In particular, electron mobility is generally higher than hole mobility, and exhibits anisotropy of up to 241%. With increasing biaxial tensile strain, both electron mobility and hole mobility decline gradually, which is mainly attributed to a strain-induced heavier effective mass. Surprisingly, it is found that carrier mobilities can be enhanced by about 147% (electrons) and 968% (holes) via a small biaxial compressive strain, which effectively produces smaller effective masses of carriers and larger elastic modulus, suggesting the possibility of achieving high mobility of monolayer SnSe over a large number of substrates. Our results highlight a new promising 2D tin-based chalcogenide material with high thermal stability and controllable superior carrier mobility, having great potential in future flexible nano-electronic devices.