Layered gallium sulfide optical properties from monolayer to CVD crystalline thin films

Interest in layered van der Waals semiconductor gallium monosulfide (GaS) is growing rapidly because of its wide band gap value between those of two-dimensional transition metal dichalcogenides and of insulating layered materials such as hexagonal boron nitride. For the design of envisaged optoelectronic, photocatalytic and photonic applications of GaS, the knowledge of its dielectric function is fundamental. Here we present a combined theoretical and experimental investigation of the dielectric function of crystalline 2H-GaS from monolayer to bulk. Spectroscopic imaging ellipsometry with micron resolution measurements are corroborated by first principle calculations of the electronic structure and dielectric function. We further demonstrate and validate the applicability of the established dielectric function to the analysis of the optical response of c-axis oriented GaS layers grown by chemical vapor deposition (CVD). These optical results can guide the design of novel, to our knowledge, optoelectronic and photonic devices based on low-dimensional GaS. (C) 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

Automated summary

In this study, the dielectric function of crystalline 2H-GaS from monolayer to bulk was investigated through a combined theoretical and experimental approach. Spectroscopic imaging ellipsometry with micron resolution measurements and first principle calculations were used to determine the dielectric function. The applicability of the established dielectric function was further demonstrated through the analysis of the optical response of GaS layers grown by chemical vapor deposition. These findings provide guidance for the design of optoelectronic and photonic devices based on low-dimensional GaS.