Energy Band Alignment of a Monolayer MoS2 with SiO2 and Al2O3 Insulators from Internal Photoemission. Issue 8 (15th January 2019)

• Record Type: Journal Article
• Authors: Shlyakhov, Ilya; Chai, Jianwei; Yang, Ming; Wang, Shijie; Afanas'ev, V. V.; Houssa, Michel; Stesmans, Andre
• Other Names: Modreanu Mircea guestEditor.; Cornet Charles guestEditor.; Durand Olivier guestEditor.; Fujiwara Hiroyuki guestEditor.; Jellison Gerald E. guestEditor.; Bell Gavin guestEditor.; Merckling Clement guestEditor.
• Is Part Of: Physica status solidi. Volume 216:Issue 8(2019)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2019-01-15
• Subjects: band alignment -- electron affinity -- electron barrier -- internal photoemission spectroscopy -- MoS2; Solid state physics -- Periodicals; Solids -- Industrial applications -- Periodicals; 530.41
• DOI: 10.1002/pssa.201800616
• Languages: English
• ISSNs: 1862-6300

Abstract

Abstract : Internal photoemission of electrons (IPE) from large area one monolayer 2H‐MoS2 films synthesized on top of amorphous (a−) SiO2 or Al2 O3 is used to determine the energy of the semiconductor valence band (VB) relative to the reference level of the insulator conduction band (CB). This allows us to compare the VB top energy in MoS2 to that of the (100)Si substrate crystal at the interface with the same insulator. Despite the CB in a–Al2 O3 is found to be ≈1 eV below that in SiO2 as measured relative to the Si VB edge, the authors observe nearly no shift of the spectral threshold in the case of IPE from the MoS2 VB. This observation indicates violation of electroneutrality at the MoS2 /a–Al2 O3 interface causing an increase in barrier by ≈1 eV. This conclusion is supported by the much weaker field dependence of the IPE threshold at the MoS2 /a–Al2 O3 interface compared to the MoS2 /a–SiO2 one, suggesting the presence of negative charges and/or interface dipoles. Therefore, the commonly accepted electron affinity rule (EAR) appears to be not appropriate to describe the band alignment at 2D/insulator interfaces. Abstract : Using internal photoemission of electrons (IPE) from a single monolayer MoS2 into insulating oxide (SiO2 or Al2 O3 ) the applicability of electron affinity rule (EAR) is examined. Despite the conduction band downshift by 1 eV when replacing SiO2 by alumina the IPE threshold remains close to 4 eV indicating that the EAR is not appropriate to describe the band alignment at 2D semiconductor/insulator interfaces.