Probing the Optical Response and Local Dielectric Function of an Unconventional Si@MoS Core-Shell Architecture.

Heterostructures of optical cavities and quantum emitters have been highlighted for enhanced light-matter interactions. A silicon nanosphere, , and MoS, , structure is one such heterostructure referred to as the core@shell architecture. However, the complexity of the synthesis and inherent difficulties to locally probe this architecture have resulted in a lack of information about its localized features limiting its advances. Here, we utilize valence electron energy loss spectroscopy (VEELS) to extract spatially resolved dielectric functions of Si@MoS with nanoscale spatial resolution corroborated with simulations. A hybrid electronic critical point is identified ∼3.8 eV for Si@MoS. The dielectric functions at the Si/MoS interface is further probed with a cross-sectioned core-shell to assess the contribution of each component. Various optical parameters can be defined via the dielectric function. Hence, the methodology and evolution of the dielectric function herein reported provide a platform for exploring other complex photonic nanostructures.