Predicted novel Janus <i>γ</i>-Ge<sub>2</sub> <i>XY</i> ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>X</mml:mi> <mml:mrow> <mml:mo>/</mml:mo> </mml:mrow> <mml:mi>Y</mml:mi> <mml:mo>=</mml:mo> </mml:math> S, Se, Te) monolayers with Mexican-hat dispersions and high carrier mobilities
Tuan V. Vu, Huynh V. Phuc, Le C. Nhan, A. I. Kartamyshev, Nguyen N. Hieu
Abstract
Abstract This work is motivated by the recent fabrication of a new four-atom-thick hexagonal polymorph from group IV monochalcogenide, so-called γ -GeSe (Lee et al 2021 Nano Lett. 21 4305). In this paper, we propose and examine the structural characteristics, electronic properties, and carrier mobility of monolayers Janus γ -Ge 2 XY ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>X</mml:mi> <mml:mrow> <mml:mo>/</mml:mo> </mml:mrow> <mml:mi>Y</mml:mi> <mml:mo>=</mml:mo> </mml:math> S, Se, or Te) based on comprehensive first-principles calculations. Monolayers γ -Ge 2 XY are confirmed to be structurally stable. Our calculations reveal that γ -Ge 2 XY monolayers are indirect semiconductors with Mexican-hat-like dispersions in the top valence band. While the effect of the electric field on the energy band dispersions of γ -Ge 2 XY monolayers is weak, the energy band dispersions are changed drastically in the presence of strain, especially compressive strain. Interestingly, a structural phase transition from semiconductor to metal is observed in γ -Ge 2 XY under compressive strain. γ -Ge 2 STe and γ -Ge 2 SeTe possess high electron mobility with values of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>3.22</mml:mn> <mml:mo>×</mml:mo> <mml:msup> <mml:mn>10</mml:mn> <mml:mn>3</mml:mn> </mml:msup> </mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>8.33</mml:mn> <mml:mo>×</mml:mo> <mml:msup> <mml:mn>10</mml:mn> <mml:mn>3</mml:mn> </mml:msup> </mml:math> cm 2 V −1 s −1 , respectively. Our findings not only explore the fundamental physical properties of γ -Ge 2 XY but also open up new opportunities in the design of high-performance electronic nanodevices based on layered nanomaterials with Mexican-hat-like dispersions.