First-principles simulation of monolayer hydrogen passivated Bi2O2S2–metal interfaces

Abstract

Monolayer (ML) MoS₂ is one of the most extensively studied two-dimensional (2D) semiconductors. However, it suffers from low carrier mobility and pervasive Schottky contact with metal electrodes. 2D semiconductor Bi₂O₂S, a sulfur analogue of 2D Bi₂O₂Se, has been prepared recently. ML fully hydrogen-passivated Bi₂O₂S₂ (Bi₂O₂S₂H₂) posseses a comparable band gap (1.92 eV) with ML MoS₂ (1.8 eV), but probably has a better device performance than ML MoS₂. Based on the density functional theory, the electron and hole mobilities of ML Bi₂O₂S₂H₂ at 300 K are calculated to be 16 447–26 699 and 264–968 cm² V⁻¹ s⁻¹, respectively. Then we firstly characterize the contact properties of ML half hydrogen-passivated Bi₂O₂S₂ (Bi₂O₂S₂H) with four bulk metal electrodes (Ti, Sc, Pd, and Pt) based on ab initio quantum transport simulation. In the lateral direction, a p-type Schottky contact is found in Pd and Pt electrodes, and the corresponding hole Schottky barrier heights (SBHs) are 0.54 and 0.99 eV, respectively. Remarkably, a coveted n-type Ohmic contact appears in Sc and Ti electrodes. Finally, the current on–off ratio of the ML hydrogen-passivated Bi₂O₂S₂ field effect transistor with a Ti electrode reaches 10⁵. Hence, the good intrinsic properties, contact properties, and large switching ability put ML hydrogen-passivated Bi₂O₂S₂ in the rank of potential channel candidates for post-silicon era field effect transistors.