The structural, electronic and optic properties in a series of M 2 XY (M = Ga, In; X,Y = S, Se, Te) Janus monolayer mate
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THE EUROPEAN PHYSICAL JOURNAL B
Regular Article
The structural, electronic and optic properties in a series of M2XY (M = Ga, In; X,Y = S, Se, Te) Janus monolayer materials based on GW and the Bethe-Salpeter equation Jianye Liu 1 , Xiuxian Yang 1 , Zhenhong Dai 1,a , Yinchang Zhao 1 , and Sheng Meng 2 1 2
Department of Physics, Yantai University, Yantai 264005, P.R. China Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, P.R. China Received 21 August 2019 / Received in final form 28 April 2020 Published online 13 July 2020 c EDP Sciences / Societ`
a Italiana di Fisica / Springer-Verlag GmbH Germany, part of Springer Nature, 2020 Abstract. Utilizing first-principles calculations, we have investigated the structural, electronic, and optic properties of a series of two-dimensional (2D) stable direct band-gap semiconductors, which are M2 XY (M = Ga, In; X,Y = S, Se, Te) in group-III-V with the Janus single layer structures. Meanwhile, the MX (M = Ga, In; X = S, Se, Te) of binary single layer structures, which are parent materials for Janus structures, have also been investigated. The electronic structures are calculated via GW0 self-consistency, and the results show that these Janus monolayer structures belong to the direct band-gap semiconductors with large band gap. In contrast to the indirect band-gap MX monolayers, it indicates that an indirect-direct band-gap transition can be realized by constructing Janus structures. Moreover, we systematically investigated the optic response properties of M2 XY Janus single layers by solving the Bethe-Salpeter equation (BSE), and the exciton absorption peaks are observed in these monolayer structures. Our results show that these Janus structure materials should be potential candidates for optoelectronic nanodevices.
1 Introduction Since the discovery and manufacture of monolayer graphene [1,2], some other two-dimensional (2D) materials, such as single-layer boron [3,4], black phosphorus [5,6] and transition-metal chalcogenides (TMDs) [7–12], etc., have aroused great interest due to their unique electronic properties and applicabilities in nanoscale device fields [8,13]. In particular, the direct band-gap semiconductors, such as single layer TMDs MX2 (M = Mo, W; X = S, Se, Te), have high carrier mobilities and suitable gap values [14], which make them become the ideal 2D optoelectronic device materials [15]. As a member of the metal chalcogenides, GaS, GaSe, GaTe, InS, InSe, and InTe have also given rise to great interest because of their electronic structures and widely broad optical response properties [16–24]. Other properties, such as lattice thermal conductivity [25], solar energy conversion [26,27], were also investigated. In addition, MX bulk materials are a class of layered structures and stacked with weak out-of-plane van der Waals (vdw) interaction layers. Thus the micromechanical cleavage technique can be used to fabricate single-layer sheets by repeatedly peeling the bulk materials and
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