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Structural, mechanical and electronic properties of two-dimensional single-layer hexagonal structures in the (1 1 1) crystal plane of IIIAs-ZnS systems (III = B, Ga and In) are studied by first-principles calculations based on density functional theory (DFT). Elastic and phonon dispersion relation display that 2D h-IIIAs systems (III = B, Ga and In) are both mechanical and dynamically stable. Electronic structures analysis show that the semiconducting nature of the 3D-IIIAs compounds is retained by their 2D single layer counterpart. Furthermore, density of states reveals the influence of σ and π bonding in the most stable geometry (planar or buckled) for 2D h-IIIAs systems. Calculations of elastic constants show that the Young's modulus, bulk modulus and shear modulus decrease for 2D h-IIIAs binary compounds as we move down on the group of elements of the periodic table. In addition, as the bond length between the neighboring cation-anion atoms increases, the 2D h-IIIAs binary compounds display less stiffness and more plasticity. Our findings can be used to understand the contribution of the σ and π bonding in the most stable geometry (planar o buckled) for 2D h-IIIAs systems. Structural and electronic properties of h-IIIAs systems as a function of the number of layers have been also studied. It is shown that h-BAs keeps its planar geometry while both h-GAs and h-InAs retained their buckled ones obtained by their single layers. Bilayer h-IIIAs present the same bandgap nature of their counterpart in 3D. As the number of layers increase from 2 to 4, the bandgap width for layered h-IIIAs decreases until they become semimetal or metal. Interestingly, these results are different to those found for layered h-GaN. The results presented in this study for single and few-layer h-IIIAs structures could give some physical insights for further theoretical and experimental studies of 2D h-IIIV-like systems.

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We found a large thermoelectric figure of merit in the hexagonal phase of 2D selenium and tellurium from first‐principles calculations. The hexagonal phase (α) is obtained from three atomic layers truncated along the [001] direction of trigonal Te and Se bulk in the equilibrium structure. We found the α‐Se structure dynamically stable. The calculated electronic structures of α‐Se and α‐Te show interesting semiconductor character for both electronic and optoelectronic applications. Furthermore, the obtained elastic properties show that hexagonal tellurene is a softer material than selenene. The thermoelectric figure of merit for hexagonal 2D phase (∼1.0) is larger than those reported for the tetragonal 2D phase (∼0.75) of selenium and tellurium. Additionally, the computed electrical and phonon transport parameters indicate that selenene and tellurene are promising thermoelectric materials; both offer an alternative to recovering residual heat and transforming it into electricity.

2D-GaAs bandgap nature and graphene opening bandgap have been investigated in unexplored Graphene/GaAs bilayer van der Waals heterostructure under both uniaxial stress along c axis and different planar strain distributions using a 551/331 supercell geometry by DFT-VdW-Tkatchenko-Scheffler method and spinorbit coupling. The 2D-GaAs bandgap nature changes from Γ-K indirect in isolated monolayer to Γ-Γ direct in Graphene/GaAs bilayer heterostructure. In the same latter physical conditions, the graphene displays a bandgap of 5.0 meV. The uniaxial stress strongly influences the graphene electronic bandgap. Symmetrical in-plane strain does not open the graphene bandgap. Nevertheless, it induces remarkable changes on the GaAs width around the Fermi level. However, when applying asymmetrical in-plane strain to graphene/GaAs, the graphene sublattice symmetry is broken, and the graphene bandgap is open at the Fermi level to a maximum width of 814 meV. This value is much higher than that reported for graphene under asymmetrical strain. The Γ-Γ direct nature of GaAs remains unchanged in Graphene/GaAs under different types of applied strain. Phonon dispersion and elastic constants analysis display the dynamical and mechanical stability of Graphene/GaAs system, respectively. The calculated mechanical properties for bilayer heterostructure are better than those of their constituent monolayers. This latter finding, together with the tunable graphene bandgap not only by the strength but also by the direction of the strain, feature the likelihood of enhancing the physical characteristics of potential graphene-based group-IIIV electronic devices by strain engineering.