Significant enhancement of piezoelectricity induced by oxygen adsorption in monolayer and multilayer MoS2

Abstract

MoS₂ has received considerable interest due to achieving coupling between its piezoelectric and semiconducting properties. However, the piezoelectricity of multilayer MoS₂ is obtained only in odd layers and decreases as the number of layers increases, which is not beneficial for designing long-term durability piezoelectric devices. In this work, we theoretically study the structural, electronic and piezoelectric properties of monolayer and multilayer MoS₂ by oxygen (O) adsorption (O@MoS₂). The monolayer O@MoS₂ is thermodynamically stable at room temperature. All considered systems are semiconductors. The total energy calculation indicates that O adsorption can stabilize the metastable stackings. In particular, in bilayer stackings, an energetically favorable configuration is obtained in parallel polarization stacking sequences under high O adsorption concentration, resulting in the e₁₁ increasing to 8.641 × 10⁻¹⁰ C m⁻¹ from 4.991 × 10⁻¹⁰ C m⁻¹ of the monolayer. Further, in trilayer stackings, the e₁₁ is enhanced to 12.252 × 10⁻¹⁰ C m⁻¹. For the vertical piezoelectric coefficients, the e₃₁ remains almost unchanged between the monolayer and multilayer systems. More significantly, the e₃₃ of the trilayer structure is increased to 7.837 × 10⁻¹⁰ C m⁻¹. Combined with the elastic stiffness, the d₃₃ is 101.632 pm V⁻¹, which reaches the level of piezoelectric coefficients in the state-of-the-art perovskites. We reveal that the high piezoelectricity is primarily from the enhanced interlayer interaction and polarization perpendicular to the basal plane. Our results reveal that the piezoelectricity of O@MoS₂ does not rely on odd and even layers and is stronger in multilayers. Thus, it has great potential in the fields of piezoelectric applications.