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The hybrid monolayer of boron nitride and graphene, namely the BC x N monolayer, has been recently revealed as a direct bandgap semiconductor with exceptional thermal, mechanical and optical properties. The integration of such monolayer with other 2D materials into a van der Waals heterostructure (VDWH), however, remains largely unexplored thus far. In this work, we investigate the electronic and structural properties of a new class of VDWH obtained via the vertical stacking of BC x N (x = 2, 6) and blue phosphorene monolayers. By using first-principle density functional theory (DFT) simulation, we show that BC x N couples to the blue phosphorene layer via weak van der Waals interactions and exhibits a type-II band alignment which is beneficial for electron-hole pair separation in photodetection and solar cell applications. Intriguingly, changing the interlayer separation induces a indirect-to-direct band gap transition which changes the band alignment types of the VDWH. The interlayer separation, which can be readily tuned via a vertical strain, thus provides a useful tuning knob for switching the heterostructures between type-I and type-II VDWHs. Our findings reveals the BC x N-based VDWH as a versatile material platform with tunable band alignments, thus opening a route towards novel VDWH-based optoelectronic devices.

Inspired by superior gas sensing properties of PtSe2 monolayer and tunable gas sensing properties of Janus MoSSe monolayer, we study the gas sensing properties of the Janus PtSSe monolayer for CO, CO2, H2O, NH3, NO and NO2 gas molecules using first-principles density functional calculations. We calculate adsorption height and adsorption energies of the gas molecules to assess the adsorption strength of the gas molecules. Then the charge transfer from PtSSe to gas molecules is evaluated. We also investigate the effects of strain and external electric field on the gas sensing properties of Janus PtSSe monolayer. We finally reveal the origin of the superior gas sensing properties from projected density of states analysis. Our results suggest that the Janus PtSSe monolayer is a promising gas sensor with superior and tunable sensing properties.

Employing density functional theory combined with the non-equilibrium Greenʼs function formalism, we systematically investigate the structural, magnetic and magnetoelectric properties of the Co2FeAl(CFA)/MgO interface, as well as the spin-dependent transport characteristics of the CFA/MgO/CFA perpendicular magnetic tunnel junctions (p-MTJs). We find that the structure of the CFA/MgO interface with the oxygen-top FeAl termination has high thermal stability, which is protected by the thermodynamic equilibrium limit. Furthermore, this structure is found to have perpendicular magnetocrystalline anisotropy (MCA). Giant electric-field-assisted modifications of this interfacial MCA through magnetoelectric coupling are demonstrated with an MCA coefficient of up to 10−7 erg V−1 cm. In addition, our non-collinear spin transport calculations of the CFA/MgO/CFA p-MTJ predict a good magnetoresistance performance of the device.