Quasiparticle Gap Renormalization Driven by Internal and External Screening in a <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi>WS</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math> Device

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 WS_{2} device. The 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 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 WS_{2}. Using GW calculations, we determine that intrinsic screening due to stronger doping in vacuum-exposed WS_{2} exceeds the external environmental screening in graphene-encapsulated WS_{2}.