The electronic band gap of a two-dimensional semiconductor within a device architecture is sensitive to variations in screening properties of adjacent materials in the device and to gate-controlled doping. Here, we employ microfocused angle-resolved photoemission spectroscopy to separate band gap renormalization effects stemming from environmental screening and electron doping during in situ gating of a single-layer ${\mathrm{WS}}_2$ device. The ${\mathrm{WS}}_2$ is supported on hexagonal boron nitride and contains a section that is exposed to vacuum and another section that is encapsulated by a graphene contact. We directly observe the doping-induced semiconductor-metal transition and band gap renormalization in the two sections of ${\mathrm{WS}}_2$. Surprisingly, a larger band gap renormalization is observed in the vacuum-exposed section than in the graphene-encapsulated—and thus ostensibly better screened—section of the ${\mathrm{WS}}_2$. Using $GW$ calculations, we determine that intrinsic screening due to stronger doping in vacuum-exposed ${\mathrm{WS}}_2$ exceeds the external environmental screening in graphene-encapsulated ${\mathrm{WS}}_2$.

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• Electronic structure
• Polarons
• Graphene
• Transition metal dichalcogenides
• Two-dimensional electron system
• GW method
• Photoemission spectroscopy