Synthesis of Ultrathin Topological Insulator beta-Ag2Te and Ag2Te/WSe2-Based High-Performance Photodetector

beta-Ag2Te has attracted considerable attention in the application of electronics and optoelectronics due to its narrow bandgap, high mobility, and topological insulator properties. However, it remains a significant challenge to synthesize 2D Ag2Te because of the non-layered structure of Ag2Te. Herein, the synthesis of large-size, ultrathin single crystal topological insulator 2D Ag2Te via the van der Waals epitaxial method for the first time is reported. The 2D Ag2Te crystal exhibits p-type conduction behavior with high carrier mobility of 3336 cm(2) V-1 s(-1) at room temperature. Taking advantage of the high mobility and perfect electron structure of Ag2Te, the Ag2Te/WSe2 heterojunctions are fabricated via mechanical stacking and show an ultrahigh rectification ratio of 2 x 10(5). Ag2Te/WSe2 photodetector also exhibits self-driven properties with a fast response speed (40 mu s/60 mu s) in the near-infrared region. High responsivity (219 mA W-1) and light ON/OFF ratio of 6 x 10(5) are obtained under the photovoltaic mode. The overall performance of the Ag2Te/WSe2 photodetector is significantly competitive among all reported 2D photodetectors. These results indicate that 2D Ag2Te is a promising candidate for future electronic and optoelectronic applications.