Band Offset and Electron Affinity of Monolayer MoSe2 by Internal Photoemission

Abstract

The electron energy band alignment of the monolayer MoSe2/oxide/Si system is characterized by internal photoemission spectroscopy, where the oxide is Al2O3 or SiO2. Raman and photoluminescence spectroscopic measurements confirm the high quality of monolayer MoSe2 exfoliated with gold film as medium. At the oxide flat-band condition, the band offset from the monolayer MoSe2 valence band maximum to the Al2O3 and SiO2 conduction band minimum are measured to be (4.10 ± 0.05) eV and (4.80 ± 0.05) eV, respectively. By referencing the recently reported band gap value of 2.18 eV for monolayer MoSe2, we obtain the electron affinity of monolayer MoSe2 to be (3.8 ± 0.1) eV on Al2O3/Si and (3.5 ± 0.1) eV on SiO2/Si. It is believed that the results from this study will help accelerate the design of electronic and optoelectronic devices that employ this class of two-dimensional materials.