RESUMO
Sulfur vacancy in MoS2 has been found to have an important influence on the performance of optoelectronic devices. Here, we study the effect of sulfur vacancy and O2 adsorption on the electronic and optical properties in the two-dimensional ferroelectric CuInP2S6. It is revealed that a defect state appears at the top of valence band with the presence of sulfur vacancy. However, when O2 is chemisorbed at sulfur vacancy, the defect state disappears. The variation of charge state and charge transfer are calculated and discussed. Although the ferroelectricity is greatly suppressed with the presence of sulfur vacancy, the ferroelectric state can be recovered when the O2 is adsorbed. Within the framework of GW + BSE method, the optical absorption edge of CuInP2S6 monolayer exhibits a red-shift for the presence of sulfur vacancy and further O2 adsorption gives rise to a blue-shift of the spectrum. Our findings have shown an effective way to improve the functionality of two-dimensional ferroelectrics via defect engineering.