Abstract
Two-dimensional semiconducting gallium sulfide (GaS) has garnered notable interest for its distinct structural and optical properties, which position it as a promising candidate material for various applications ranging from photodetection and photovoltaics to nonlinear frequency conversion. In this work, we determined the out-of-plane longitudinal sound velocity, , via impulsive time-domain femtosecond broadband Brillouin scattering measurements performed on a single flake-like GaS crystal. We obtained a value (3140 ± 20) m/s, which yields an out-of-plane compressive elastic constant, C (33)= (38.1 ± 0.5) GPa.