Fapeng Sun,Wenting Hong,Xu He,Chuanyong Jian,Qiankun Ju,Qian Cai,Wei Liu
β-Ag 2 Te 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 Ag 2 Te because of the non-layered structure of Ag 2 Te. Herein, the synthesis of large-size, ultrathin single crystal topological insulator 2D Ag 2 Te via the van der Waals epitaxial method for the first time is reported. The 2D Ag 2 Te 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 Ag 2 Te, the Ag 2 Te/WSe 2 heterojunctions are fabricated via mechanical stacking and show an ultrahigh rectification ratio of 2 × 10 5 . Ag 2 Te/WSe 2 photodetector also exhibits self-driven properties with a fast response speed (40 µs/60 µs) in the near-infrared region. High responsivity (219 mA W −1 ) and light ON/OFF ratio of 6 × 10 5 are obtained under the photovoltaic mode. The overall performance of the Ag 2 Te/WSe 2 photodetector is significantly competitive among all reported 2D photodetectors. These results indicate that 2D Ag 2 Te is a promising candidate for future electronic and optoelectronic applications.
Polymorphic phase transition is an essential phenomenon in condensed matter that the physical properties of materials may undergo significant changes due to the structural transformation. Phase transition has thus become an important means and dimension for regulating material properties. Herein, this study demonstrates the pressure-induced multi-transition of both structure and physical properties in violet phosphorus, a novel phosphorus allotrope. Under compression, violet phosphorus undergoes sequential polymorphic phase transitions. Concomitant with the first phase transition, violet phosphorus exhibits emergent insulator–metal transition, superconductivity, and dramatic switching from positive to negative photoconductivity. Remarkably, the resistance of violet phosphorus shows a sudden drop of around 10 7 along with the phase transition. In addition, piezochromism from translucent red to opaque black and suppression of photoluminescence are observed upon compression. Of particular interest is that the sample irreversibly transforms into black phosphorus with a pronounced discrepancy in physical properties from the pristine violet phosphorus after decompression. The abundant polymorphic transitions and property changes in violet phosphorus have significant implications for designing novel pressure-responsive electronic/optoelectronic devices and exploring concealed polymorphic transition materials.
危险品化学品经营许可证（带存储）