Structural evolution and optoelectronic applications of multilayer silicene

Despite the recent progress on two-dimensional multilayer materials (2DMMs) with weak interlayer interactions, the investigation of 2DMMs with strong interlayer interactions is far from sufficient. Here, we report on first-principles calculations that clarify the structural evolution and optoelectronic properties of such a 2DMM, multilayer silicene. With our global optimization algorithm, we discover the existence of rich dynamically stable multilayer silicene phases, whose stability is closely related to the extent of sp3 hybridization that can be evaluated by average bonds and effective bond angles. Stable Si(111) surface structures are obtained when the silicene thickness gets up to four, showing the critical thickness for a structural evolution. We also find that multilayer silicene with π-bonded surfaces presents outstanding optoelectronic properties for solar cells and optical fiber communications due to the incorporation of sp2-type bonds in the sp3-type bond dominated system. This study helps to complete the picture of the structure and related property evolution of 2DMMs with strong interlayer interactions.