Sulfur-Doped Black Phosphorus Field-Effect Transistors with Enhanced Stability

Black phosphorus (BP) has drawn great attention owing to its tunable band gap depending on thickness, high mobility, and large I-on/I-off Toff ratio, which makes BP attractive for using in future two-dimensional electronic and optoelectronic devices. However, its instability under ambient conditions poses challenge to the research and limits its practical applications. In this work, we present a feasible approach to suppress the degradation of BP by sulfur (5) doping. The fabricated S-doped BP few layer field-effect transistors (FETs) show more stable transistor performance under ambient conditions. After exposing to air for 21 days, the charge-carrier mobility of a representative S-doped BP FETs device decreases from 607 to 470 cm(2) V-1 s(-1) (remained as high as 77.4%) under ambient conditions and a large I-on/I-off ratio of similar to 10(3) is still retained. The atomic force microscopy analysis, including surface morphology, thickness, and roughness, also indicates the lower degradation rate of S-doped BP compared to BP. First-principles calculations show that the dopant S atom energetically prefers to chemisorb on the BP surface in a dangling form and the enhanced stability of S-doped BP can be ascribed to the downshift of the conduction band minimum of BP below the redox potential of O-2/O-2(-). Our work suggests that S doping is an effective way to enhance the stability of black phosphorus.