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Self-passivated ultra-thin SnS layers via mechanical exfoliation and post-oxidation

Abstract

Remarkable optical/electrical features are expected in two-dimensional group-IV monochalcogenides (MXs; M=Sn/Ge and X=S/Se) with a uniquely distorted layered structure. The lone pair electrons in the group-IV atoms are the origin of this structural distortion, while they also cause a strong interlayer force and high chemical reactivity. The fabrication of chemically stable few-to-monolayer MX has been a significant challenge. We have observed that, once the SnS surface is oxidized, the SnOx top layer works as a passivation for the SnS layer underneath. In this work, the SnOx/SnS hetero-structure is studied structurally, optically, and electrically. When a tape-exfoliated bulk SnS is oxygen-annealed under a reduced pressure at 10 Pa, surface oxidation and SnS sublimation proceed simultaneously, resulting in a monolayer-thick SnS layer with the SnOx passivation layer. The field-effect transistor of nine-layer SnS prepared via mechanical exfoliation exhibits a p-type characteristic because of intrinsic Sn vacancies, whereas ambipolar behavior is observed for the monolayer-thick SnS obtained via oxygen annealing probably owing to the additional n-type doping by S vacancies. This work on monolayer-thick SnS fabrication can be applied to other unstable lone pair analogues and can facilitate future research on MXs.

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Publication details

The article was received on 08 Aug 2018, accepted on 06 Nov 2018 and first published on 07 Nov 2018


Article type: Paper
DOI: 10.1039/C8NR06390G
Citation: Nanoscale, 2018, Accepted Manuscript
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    Self-passivated ultra-thin SnS layers via mechanical exfoliation and post-oxidation

    N. Higashitarumizu, H. Kawamoto, M. Nakamura, K. Shimamura, N. Ohashi, K. Ueno and K. NAGASHIO, Nanoscale, 2018, Accepted Manuscript , DOI: 10.1039/C8NR06390G

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