title: Investigation of band-offsets at monolayer-multilayer MoS₂ junctions by scanning photocurrent microscopy.
abstract: The thickness-dependent band structure of MoS2 implies that discontinuities in energy bands exist at the interface of monolayer (1L) and multilayer (ML) thin films. The characteristics of such heterojunctions are analyzed here using current versus voltage measurements, scanning photocurrent microscopy, and finite element simulations of charge carrier transport. Rectifying I-V curves are consistently observed between contacts on opposite sides of 1L/ML junctions, and a strong bias-dependent photocurrent is observed at the junction. Finite element device simulations with varying carrier concentrations and electron affinities show that a type II band alignment at single layer/multilayer junctions reproduces both the rectifying electrical characteristics and the photocurrent response under bias. However, the zero-bias junction photocurrent and its energy dependence are not explained by conventional photovoltaic and photothermoelectric mechanisms, indicating the contributions of hot carriers.
authors: †Department of Materials Science and Engineering, ‡Department of Chemistry, §Department of Medicine, and ∥Materials Research Center, Northwestern University, Evanston, Illinois 60208, United States.
authors: Sarah L
authors: SL
authors: Howell
authors: †Department of Materials Science and Engineering, ‡Department of Chemistry, §Department of Medicine, and ∥Materials Research Center, Northwestern University, Evanston, Illinois 60208, United States.
authors: Deep
authors: D
authors: Jariwala
authors: †Department of Materials Science and Engineering, ‡Department of Chemistry, §Department of Medicine, and ∥Materials Research Center, Northwestern University, Evanston, Illinois 60208, United States.
authors: Chung-Chiang
authors: CC
authors: Wu
authors: †Department of Materials Science and Engineering, ‡Department of Chemistry, §Department of Medicine, and ∥Materials Research Center, Northwestern University, Evanston, Illinois 60208, United States.
authors: Kan-Sheng
authors: KS
authors: Chen
authors: †Department of Materials Science and Engineering, ‡Department of Chemistry, §Department of Medicine, and ∥Materials Research Center, Northwestern University, Evanston, Illinois 60208, United States.
authors: Vinod K
authors: VK
authors: Sangwan
authors: †Department of Materials Science and Engineering, ‡Department of Chemistry, §Department of Medicine, and ∥Materials Research Center, Northwestern University, Evanston, Illinois 60208, United States.
authors: Junmo
authors: J
authors: Kang
authors: †Department of Materials Science and Engineering, ‡Department of Chemistry, §Department of Medicine, and ∥Materials Research Center, Northwestern University, Evanston, Illinois 60208, United States.
authors: Tobin J
authors: TJ
authors: Marks
authors: †Department of Materials Science and Engineering, ‡Department of Chemistry, §Department of Medicine, and ∥Materials Research Center, Northwestern University, Evanston, Illinois 60208, United States.
authors: Mark C
authors: MC
authors: Hersam
authors: †Department of Materials Science and Engineering, ‡Department of Chemistry, §Department of Medicine, and ∥Materials Research Center, Northwestern University, Evanston, Illinois 60208, United States.
authors: Lincoln J
authors: LJ
authors: Lauhon
keywords: MoS2; SPCM; TMDC; dichalcogenides; energy conversion; field-effect transistor; gate-tunable; heterojunction; photothermal; photovoltaic; scanning photocurrent microscopy; two-dimensional