First-principles investigation of the electronic, piezoelectric and transport properties of InSeX (X = Cl, Br, I) monolayers

Abstract

First-principles calculation was performed to study the InSeX (X = Cl, Br, and I) monolayers, which are formed by the breaking of In--In bonds in the InSe monolayers through full halogenation. The isolated InSeX monolayers have Se--In--X stacking configuration with the buckled honeycomb structure maintained by newly formed Se-sp$^3$ hybrid orbitals. InSeX (X = Cl, Br, and I) monolayers have good mechanical properties with Young's modulus in the range of 28.69--33.44 N m$^{-1}$ and Poisson's ratio of nearly 0.30. Their in-plane structures are expected to be highly isotropic due to the independence of elastic parameters on the angle of applied strains. High carrier concentration (10$^{20}$ cm$^{-3}$) and scattering mechanisms greatly reduce the mobility of these monolayers, especially at high temperature. However, the InSeI monolayer appear to be promising material because its electron mobility is rather high, 10.82--217.33 cm$^2$ V$^{-1}$ s$^{-1}$, at temperature of 50--400~K. InSeX (X = Cl, Br, and I) monolayers are also promising piezoelectric materials with high in-plane piezoelectric coefficients $e_{11}$ in the range of 3.34--5.60 $\times$ 10$^{-10}$~C/m and $d_{11}$ of 14.90--33.50 pm/V. Current study provides the mechanism of how isolated InSeX (X = Cl, Br, and I) monolayers are formed and stabilized, which is useful to expand the new subclass of 2D materials by apply the same procedure for group XIII monochalcoghttps://mc.manuscriptcentral.com/na#enides (MX, where M = B, Al, Ga, In, Tl and X = S, Se, Te). The InSeX (X = Cl, Br, and I) monolayers are also promising for wide range of application because of the broad tunability of bandgap (1.36--2.94 eV), band edge positions, and work function (4.80--7.80 eV).