Suppression of substrate-induced charge doping in hBN-encapsulated monolayer WS₂

Strong coupling between a two-dimensional material and substrate is problematic in that interlayer charge transfer at the interface often complicates optoelectronic device applications. Such substrate-induced charge doping effects are particularly large for two-dimensional materials on SiO₂/Si substrate. Here, we report a Raman study of monolayer WS₂ encapsulated with hexagonal boron nitride (hBN) to unveil substrate-related charge doping phenomena under the influence of laser irradiation. Raman correlation analysis between the E^′ and A₁^′ phonon frequencies of WS₂ reveals that the encapsulation of WS₂ with hBN leads to a screening of electron transfer from SiO₂ to WS₂. Further, photo-induced charge doping in WS₂ is completely suppressed by hBN encapsulation. Our results demonstrate that understanding the photo-induced charge doping effects in two-dimensional heterostructures is useful in characterizing the role of hBN encapsulation and, thus, shed light on design strategies for efficient two-dimensional optoelectronic applications where a precise control of charge doping is required.