Revealing layer-dependent interlayer interactions by doping effect on graphene in WSe2/N-layer graphene heterostructures using Raman and photoluminescence spectroscopy

Assembling layered materials in the form of vertically stacked heterostructures has enabled the combination of various properties from different two-dimensional (2D) materials, which is receiving a great deal of attention for investigating novel physical phenomena and emerging a facile way to fabricate promising highly tailored architectures. In this study, we employ Raman and photoluminescence (PL) spectroscopy to systematically investigate the influence of thickness on interlayer interaction in WSe2/n-layer graphene (WSe2/nL-Gr, n = 1, 2, 3, 4) heterostructures. It is found that the charge carrier concentration of graphene can be significantly affected by distinct interlayer coupling originated from heterostructure interface. The observed varying doping levels in graphene as layer number (nL) increases from 1L to 4L are quantitatively studied by considering the screening effects and band structure. On the other hand, the corresponding change of electronic band structure of WSe2 is further discussed after introducing graphene, PL intensity in WSe2/N-Gr heterostructures is quenched by more than 2 orders of magnitude which suggests ultra-efficient interlayer charge transfer occurs. Meanwhile, the various screening effects from graphene with different nL can account for the evolution of band structure of WSe2, which is in good agreement with the layer-dependent doping effect in graphene. This work offers a comprehensive investigation on nL dependence of interface coupling in WSe2/N-Gr heterostructures. Our observations also demonstrate that the physical properties of each component in heterostructures can be effectively tuned by the other one, which will drive the development of heterostructures in electronic and optoelectronic devices.