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Determination of band offsets, hybridization and exciton binding in 2D semiconductor heterostructures

μ-ARPES allowes to measure electronic band structure of small artifitially made layered heterostructures of 2D materials as shown in a work of
N. Wilson et al, Sci. Adv.  3, e1601832, (2017)

We determine the key unknown parameters in MoSe2/WSe2 heterobilayers by using rational device design and submicrometer angle-resolved photoemission spectroscopy (μ-ARPES) in combination with photoluminescence. We find that the bands in the K-point valleys are weakly hybridized, with a valence band offset of 300 meV, implying type II band alignment. We deduce that the binding energy of interlayer excitons is more than 200 meV, an order of magnitude higher than that in analogous GaAs structures.Hybridization strongly modifies the bands at Γ, but the valence band edge remains at the K points. We also find that the spectrum of a rotationally aligned heterobilayer reflects a mixture of commensurate and incommensurate domains.

These results directly answer many outstanding questions about the electronic nature of MoSe2/WSe2 heterobilayers and demonstrate a practical approach for high spectral resolution in ARPES of device-scale structures.

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Determination of band offsets, hybridization and exciton binding in 2D semiconductor heterostructures , N. Wilson et al, Sci. Adv.,  3, e1601832, (2017)

Ultima modifica il Lunedì, 09 Aprile 2018 14:43