First-principles prediction of a new ground state for surface-oxidized phosphorene with remarkable piezoelectricity

Abstract

In this paper, a new ground state (Pca21-PO) of surface-oxidized phosphorene is identified from a series of possible crystalline configurations. The crystalline structure of Pca21-PO is based on the previously proposed θ-P with further distortion. It is predicted to be more favorable than the previously proposed Pmn21-PO and confirmed to be dynamically stable. The calculated band structures show that Pca21-PO is an indirect band gap semiconductor with a gap of 0.607 eV and 1.396 eV based on DFT-PBE and HSE06 methods, respectively. It is a potential piezoelectric material with coefficients of −9.38 pm V−1, 50.32 pm V−1, 0.83 pm V−1 and –0.09 pm V−1 for d11, d12, d21 and d22, respectively. These coefficients are comparable to those of group-IV monochalcogenides and more remarkable than that of the experimental MoS2. In particular, Pca21-PO possesses piezoelectric effect in arbitrary direction in view of the absence of both inverse and mirror symmetries, which can be considered as a potential material for applications in nano-scale devices, such as sensors, actuators, electric field generators and any other applications requiring electrical and mechanical energy conversion.