Pressure induced structure-property tuning of two dimensional materials

Controlling the band gap by tuning the lattice structure through pressure engineering is a relatively new route for tailoring the optoelectronic properties of two dimensional (2D) materials. Here we investigate the electronic and lattice vibrational dynamics of the distorted monolayer 1T-MoS₂ (1T') and the monolayer 2H-MoS₂ via a diamond anvil cell (DAC) and density functional theory (DFT) calculations. The direct optical band gap of the monolayer 2H-MoS₂ increases by 11.7% from 1.85 eV to 2.08 eV, which is the highest reported for a 2D transition metal dichalcogenide (TMD) material. DFT calculations reveal a subsequent decrease in the band gap with eventual metallization of the monolayer 2H-MoS₂, an overall complex structure-property relation due to the rich band structure of MoS₂. Remarkably, the metastable 1T'-MoS₂ metallic state remains invariant with pressure, with the J₂, A₁[subscript g], and E₂[subscript g] modes becoming dominant at high pressures. This substantial reversible tunability of the electronic and vibrational property of the MoS₂ family can be extended to other 2D TMDs. These results present an important advance toward controlling the band structure and optoelectronic properties of monolayer MoS₂ via pressure, which has vital implications for enhanced device applications.