Revealing the Polaron State at the MoS2/TiO2 Interface

Interfacial polarons determine the distribution of free charges at the interface and thus play important roles in manipulating the physicochemical properties of hybridized polaronic materials. In this work, we investigated the electronic structures at the atomically flat interface of the single-layer MoS2 (SL-MoS2) on the rutile TiO2 surface using high-resolution angle-resolved photoemission spectroscopy. Our experiments directly visualized both the valence band maximum and the conduction band minimum (CBM) of SL-MoS2 at the K point, which clearly defines a direct bandgap of similar to 2.0 eV. Detailed analyses corroborated by density functional theory calculations demonstrated that the CBM of MoS2 is formed by the trapped electrons at the MoS2/TiO2 interface that couple with the longitudinal optical phonons in the TiO2 substrate through an interfacial Frohlich polaron state. Such an interfacial coupling effect may register a new route for tuning the free charges in the hybridized systems of two-dimensional materials and functional metal oxides.

Automated summary

In this study, the electronic structures at the atomically flat interface of single-layer MoS2 (SL-MoS2) on rutile TiO2 surface were investigated using high-resolution angle-resolved photoemission spectroscopy. The valence band maximum and the conduction band minimum of SL-MoS2 at the K point were directly visualized, indicating a direct bandgap of approximately 2.0 eV. Detailed analyses and density functional theory calculations confirmed that the conduction band minimum of MoS2 is formed by trapped electrons at the MoS2/TiO2 interface coupling with longitudinal optical phonons in the TiO2 substrate through an interfacial Frohlich polaron state. This interfacial coupling effect may provide a new route for tuning free charges in hybridized systems of two-dimensional materials and functional metal oxides.