Photophysics and Electronic Structure of Lateral Graphene/MoS₂ and Metal/MoS₂ Junctions

Abstract

Integration of semiconducting transition metal dichalcogenides (TMDs) into functional optoelectronic circuitries requires an understanding of the charge transfer across the interface between the TMD and the contacting material. Here, we use spatially resolved photocurrent microscopy to demonstrate electronic uniformity at the epitaxial graphene/molybdenum disulfide (EG/MoS2) interface. A 10 larger photocurrent is extracted at the EG/MoS2 interface when compared to metal (Ti/Au) /MoS2 interface. This is supported by semi-local density-functional theory (DFT), which predicts the Schottky barrier at the EG/MoS2 interface to be ~2 lower than Ti/MoS2. We provide a direct visualization of a 2D material Schottky barrier through combination of angle resolved photoemission spectroscopy with spatial resolution selected to be ~300 nm (nano-ARPES) and DFT calculations. A bending of ~500 meV over a length scale of ~2-3 µm in the valence band maximum of MoS2 is observed via nano-ARPES. We explicate a correlation between experimental demonstration and theoretical predictions of barriers at graphene/TMD interfaces. Spatially resolved photocurrent mapping allows for directly visualizing the uniformity of built-in electric fields at heterostructure interfaces, providing a guide for microscopic engineering of charge transport across heterointerfaces. This simple probe-based technique also speaks directly to the 2D synthesis community to elucidate electronic uniformity at domain boundaries alongside morphological uniformity over large areas.

Epitaxy of 2D Materials toward Single Crystals

“…[ 172 , 173 ] Although there are no one‐to‐one chemical bonds formation, the vdW interaction between the overlapped edges of graphene and TMDC materials could also guide the TMDC orientations under well‐controlled conditions. [ 174 , 175 ]…”

MoS2-based nanocomposites: synthesis, structure, and applications in water remediation and energy storage: a review

“…The Cs ion passes a charge to the MoS 2 system in the 1 T, 3R, and 2H stages, respectively, of 0.85, 0.86, and 0.86 |e|, indicating the creation of ionic bonding. Subramanian et al (2020) predicted that the Schottky barrier at the epitaxial graphene/molybdenum disulfide interface would be lesser than that of the metal. To predict the Schottky barrier from first principles, estimates of work functions of the individual components pristine Ti, MoS 2 , graphene, and relaxed heterointerfaces (epitaxial graphene/ MoS 2 and Ti/MoS 2 ) are needed.…”

Photoinduced Anomalous Electron Transfer Dynamics at a Lateral MoS2–Graphene Covalent Junction

“…Lee et al 36 than that of the vdW junction, due to an internal electric field promoting charge separation. 37 Although many experimental efforts have been devoted to study the device properties of different lateral TMDs/graphene heterojunctions, the detailed mechanism of the ultrafast interlayer charge transfer dynamics is unclear. Therefore, an atomistic time-domain study of the photoinduced electron transfer (ET) and the competing energy relaxation processes are needed to uncover the microscopic mechanisms for the improved optoelectronic performance.…”

“…The approach has been applied to study the photoexcitation dynamics in a broad range of systems, including TiO 2 sensitized with semiconducting 40,41 and metallic nanoparticles, 42 as well as MoS 2 , 41 graphene 43 and graphene quantum dots, 44 TMDs junctions, 15,45 perovskites, 46,47 etc. 48−50 Motivated by the recent experiments, 13,35,37,51 we performed an ab initio time-domain study to investigate the photoinduced ET and electron−phonon energy relaxation processes at the lateral MoS 2 −graphene junction. The simulations show that the electron injection from MoS 2 to graphene takes place within an ultrafast time scale of 200 fs due to a high density of acceptor states and strong NA coupling.…”

“…Lee et al . have reported that the photocurrent generated in the lateral MoS 2 –graphene heterojunction is 500 times larger than that of the vdW junction, due to an internal electric field promoting charge separation . Although many experimental efforts have been devoted to study the device properties of different lateral TMDs/graphene heterojunctions, the detailed mechanism of the ultrafast interlayer charge transfer dynamics is unclear.…”