Abstract

Understanding interfacial interactions in two-dimensional (2D) heterostructures is essential for advancing optoelectronic and quantum technologies. Here, we investigate metal-organic chemical vapor deposition (MOCVD)-grown WSe₂ films (1–5 layers) on graphene/SiC substrates, directly compared to exfoliated WSe₂ on SiO2, using Raman and photoluminescence (PL) spectroscopy complemented by atomic force microscopy. Raman results reveal compressive strain and interfacial charge transfer in WSe₂/graphene heterostructures, evidenced by blue-shifted phonon modes and the emergence of higher-order layer breathing modes absent on SiO2. Accompanying shifts and attenuation of graphene’s G and 2D modes with increasing WSe₂ thickness indicate progressive p-type doping of graphene and n-type doping of WSe₂ due to interfacial electron transfer. PL measurements show strong quenching in monolayer WSe₂ on graphene caused by ultrafast charge transfer and Forster resonance energy transfer (FRET), while multilayers recover emissions relative to SiO₂-supported flakes. Interestingly, exciton behavior differs strongly between substrates: on SiO2, A and B exciton energies shift markedly with thickness, whereas on graphene they remain nearly pinned. This stability reflects the combined effects of graphene’s strong screening and charge-transfer-induced free-carrier screening, with strain playing only a minor role. This comparison shows that graphene, unlike SiO2, acts as an active interfacial partner that stabilizes excitonic states, offering new opportunities for engineering the optical response of 2D heterostructures.

Abstract

Understanding interfacial interactions in two-dimensional (2D) heterostructures is essential for advancing optoelectronic and quantum technologies. Here, we investigate metal-organic chemical vapor deposition (MOCVD)-grown WSe₂ films (1–5 layers) on graphene/SiC substrates, directly compared to exfoliated WSe₂ on SiO2, using Raman and photoluminescence (PL) spectroscopy complemented by atomic force microscopy. Raman results reveal compressive strain and interfacial charge transfer in WSe₂/graphene heterostructures, evidenced by blue-shifted phonon modes and the emergence of higher-order layer breathing modes absent on SiO2. Accompanying shifts and attenuation of graphene’s G and 2D modes with increasing WSe₂ thickness indicate progressive p-type doping of graphene and n-type doping of WSe₂ due to interfacial electron transfer. PL measurements show strong quenching in monolayer WSe₂ on graphene caused by ultrafast charge transfer and Forster resonance energy transfer (FRET), while multilayers recover emissions relative to SiO₂-supported flakes. Interestingly, exciton behavior differs strongly between substrates: on SiO2, A and B exciton energies shift markedly with thickness, whereas on graphene they remain nearly pinned. This stability reflects the combined effects of graphene’s strong screening and charge-transfer-induced free-carrier screening, with strain playing only a minor role. This comparison shows that graphene, unlike SiO2, acts as an active interfacial partner that stabilizes excitonic states, offering new opportunities for engineering the optical response of 2D heterostructures.

Abstract

Understanding interfacial interactions in two-dimensional (2D) heterostructures is essential for advancing optoelectronic and quantum technologies. Here, we investigate metal-organic chemical vapor deposition (MOCVD)-grown WSe₂ films (1–5 layers) on graphene/SiC substrates, directly compared to exfoliated WSe₂ on SiO2, using Raman and photoluminescence (PL) spectroscopy complemented by atomic force microscopy. Raman results reveal compressive strain and interfacial charge transfer in WSe₂/graphene heterostructures, evidenced by blue-shifted phonon modes and the emergence of higher-order layer breathing modes absent on SiO2. Accompanying shifts and attenuation of graphene’s G and 2D modes with increasing WSe₂ thickness indicate progressive p-type doping of graphene and n-type doping of WSe₂ due to interfacial electron transfer. PL measurements show strong quenching in monolayer WSe₂ on graphene caused by ultrafast charge transfer and Forster resonance energy transfer (FRET), while multilayers recover emissions relative to SiO₂-supported flakes. Interestingly, exciton behavior differs strongly between substrates: on SiO2, A and B exciton energies shift markedly with thickness, whereas on graphene they remain nearly pinned. This stability reflects the combined effects of graphene’s strong screening and charge-transfer-induced free-carrier screening, with strain playing only a minor role. This comparison shows that graphene, unlike SiO2, acts as an active interfacial partner that stabilizes excitonic states, offering new opportunities for engineering the optical response of 2D heterostructures.

Abstract

Understanding interfacial interactions in two-dimensional (2D) heterostructures is essential for advancing optoelectronic and quantum technologies. Here, we investigate metal-organic chemical vapor deposition (MOCVD)-grown WSe₂ films (1–5 layers) on graphene/SiC substrates, directly compared to exfoliated WSe₂ on SiO2, using Raman and photoluminescence (PL) spectroscopy complemented by atomic force microscopy. Raman results reveal compressive strain and interfacial charge transfer in WSe₂/graphene heterostructures, evidenced by blue-shifted phonon modes and the emergence of higher-order layer breathing modes absent on SiO2. Accompanying shifts and attenuation of graphene’s G and 2D modes with increasing WSe₂ thickness indicate progressive p-type doping of graphene and n-type doping of WSe₂ due to interfacial electron transfer. PL measurements show strong quenching in monolayer WSe₂ on graphene caused by ultrafast charge transfer and Forster resonance energy transfer (FRET), while multilayers recover emissions relative to SiO₂-supported flakes. Interestingly, exciton behavior differs strongly between substrates: on SiO2, A and B exciton energies shift markedly with thickness, whereas on graphene they remain nearly pinned. This stability reflects the combined effects of graphene’s strong screening and charge-transfer-induced free-carrier screening, with strain playing only a minor role. This comparison shows that graphene, unlike SiO2, acts as an active interfacial partner that stabilizes excitonic states, offering new opportunities for engineering the optical response of 2D heterostructures.