A New Monolayer ZrSe2 with High Electron Mobility and Excellent Optical Absorption Properties from the High-Pressure Phase

Pressure, as an effective method of obtaining new crystal structures without introducing any impurities, has attracted significant attention from the scientific community. Here, we employed first-principles calculations to investigate the structural evolution of the bulk ZrSe2 under hydrostatic pressure and discovered a series of pressure-induced phase transitions. The ambient-pressure P3̅m1 phase transforms to a monoclinic P21/m phase at 5 GPa, and further to an orthorhombic I4/mmm phase at 9 GPa. The P3̅m1 and P21/m phases exhibit semiconductor properties, while I4/mmm phase is metal, which realizes a semiconductor-to-metal transition under compression. Besides, the P21/m phase still maintains a layered crystal structure, similar to the ambient-pressure P3̅m1 phase. The calculated exfoliation energy of 34.49 meV/Å2 (0.55 J/m2) suggests that a two-dimensional (2D) monolayer ZrSe2 can be cleaved from the monoclinic P21/m high-pressure bulk phase. The new 2D monolayer ZrSe2 exhibits good dynamical, thermal, and mechanical stability, and possesses a moderate band gap of about 0.918 eV. More importantly, the monolayer ZrSe2 shows very high electron mobility of ∼2.6 × 103 cm2 V–1 s–1, and excellent visible-light optical absorption ability of ∼105 cm–1. Such excellent electrical transport and optical properties indicate that the monolayer ZrSe2 is a promising material for potential applications in high-performance nanoelectronic and optoelectronic devices. The present study not only reveals the pressure-induced phase transitions in ZrSe2 but also provides a clue to obtain a novel 2D monolayer material with excellent optoelectronic performance for technological applications.