Surface coordination modification and electrical properties of few-layer black phosphorus exfoliated by the liquid-phase method

Abstract Black phosphorus (BP) is a novel multifunctional two-dimensional semiconductor material, which has wide application prospects in nano-electronic devices and optoelectronic devices. However, its poor environmental stability hinders its industrial applications. In this work, liquid exfoliation method was employed to isolate few-layer BP in N-methyl-2-pyrrolidone (NMP), and a titanium sulfonate ligand (TiL4) was synthesized to coordinate with BP to prevent oxidation in air and water. We have shown that TiL4-modified BP nanoplates present the excellent stability against water and oxygen due to the passivation of lone pair electrons in P atoms. The current-voltage curves, which do not change with temperature, indicates that surface coordination modification may passivate the defects or impurities on surfaces of few-layer BP and inhibits the production of carriers from the ionization of these defects or impurities, and the carrier migration mobility is also greatly affected. These results indicated a possible method to tailor the electrical properties of few-layer BP by the surface coordination coverage of titanium sulfonate ligand.