Effects of Interlayer Coupling and Band Offset on Second Harmonic Generation in Vertical MoS/MoSSe Structures.

Noncentrosymmetric monolayers (MLs) of transition metal dichalcogenides (TMDCs) and their 3-type vertical stacks provide an ideal platform for studying atomic-scale nonlinear light-matter interaction in terms of second harmonic generation (SHG). Unlike the case of MLs, SHG from artificial stacks can be nontrivially affected by interlayer coupling and band offset between the constituent MLs, where the latter occurs for band-gap-engineered vertical heterostructures (VHs). In order to study these effects, we produced different sets of 3-type homobilayers (homo-BLs) and heterobilayers (hetero-BLs) composed of MoS and its ternary alloy MoSSe.