Photophysics and Electronic Structure of Lateral Graphene/$MoS_2$ and Metal/$MoS_2$ Junctions

S. Subramanian, Q. T. Campbell, S. K. Moser, J. Kiemle, P. Zimmermann, P. Seifert, F. Sigger, D. Sharma, H. Al-Sadeg, M. Labella, D. Waters, R. M. Feenstra, R. J. Koch, C. Jozwiak, A. Bostwick, E. Rotenberg, I. Dabo, A. W. Holleitner, T. E. Beechem, U. Wurstbauer, and J. A. Robinson

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/$MoS_2$) interface. A 10× larger photocurrent is extracted at the EG/$MoS_2$ interface when compared to the metal (Ti/Au)/$MoS_2$ interface. This is supported by semi-local density functional theory (DFT), which predicts the Schottky barrier at the EG/$MoS_2$ interface to be ∼2× lower than that at Ti/$MoS_2$. 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.

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