This work reports the interlayer difference of exciton and phonon performance between the top and bottom layer of a bilayer-stacked two-dimensional materials structure (BSS). Through photoluminescence (PL) and Raman spectroscopy, we find that, compared to that of the bottom layer, the top layer of BSS demonstrates PL redshift, Raman ${\mathrm{E}}_{2\mathrm{g}}^1$ mode redshift, and lower PL intensity. Spatial inhomogeneity of PL and Raman are also observed in the BSS. Based on theoretical analysis, these exotic effects can be attributed to substrate-coupling-induced strain and doping. Our findings provide pertinent insight into film–substrate interaction, and are of great significance to researches on bilayer-stacked structures including twisted bilayer structure, Van der Waals hetero- and homo-structure.

The twist-angle dependence of exciton absorption in a molybdenum disulfide (MoS₂)/graphene heterostructure (MGH) is reported. Using photoluminescence (PL) spectroscopy, we found that, as the twist angle increased, the MGH demonstrated an enhancement of PL intensity and a peak position blueshift, indicating that the exciton radiative recombination was positively correlated with the twist angle. In addition, optical reflectance measurements were performed in order to investigate the exciton absorption in the MGH. It was found that the reflectance of MGH samples was twist-angle dependent at wavelengths of 620 and 670 nm, which corresponds to the PL peak positions of MoS₂. This was attributed to the change in interlayer charge transfer for different twist angles. Our findings confirm the tunability of the electronic structure in MGHs via the interlayer twist, which enriches our understanding of interlayer coupling and is important for the future development of electronic and optoelectronic devices based on 2D material heterostructures.