Combination of cryo-mediated and salt-assisted liquid-phase exfoliation for GaSe nanosheets preparation with absorption coefficient estimation via Raman signal attenuation

In this study, a novel preparation method combining cryo-mediated method and salt-assisted liquid-phase exfoliation is presented for the preparation of Gallium Selenide (GaSe) nanosheets and the absorption coefficient are estimated by the Raman signal attenuation method on silicon substrates.It was found that Potassium citrate (C₆H₅K₃O₇·H₂O) as an accelerator increased the lateral size of GaSe nanosheets, while employing liquid nitrogen as a cryo-mediation significantly reduced the surface roughness of the nanosheets. Furthermore, a correlation exists between the duration of cryo-pretreatment and the thickness distribution of GaSe nanosheets.Using the absorption overlayer model, the study experimentally determined more accurate absorption coefficient of 2D GaSe nanosheets by analyzing the changes in Raman signal intensity on a silicon substrate induced by GaSe nanosheets with varying thicknesses, resulting in an average absorption coefficient of 5.68×10⁴ cm⁻¹.This study introduces a novel approach to prepare GaSe and other two-dimensional (2D) material nanosheets with large size and low roughness, based on which the absorption coefficient of GaSe nanosheets are also determined in a more precise way.