Two-dimensional (2D) magnetic materials are the key to
the development
of the new generation in spintronics technology and engineering multifunctional
devices. Herein, the electronic, spin-resolved transmission, and gas
sensing properties of the 2D g-C4N3/MoS2 van der Waals (vdW) heterostructure have been investigated
by using density functional theory with non-equilibrium Green’s
function method. First, the g-C4N3/MoS2 vdW heterostructure demonstrates ferromagnetic half-metallicity
and superior adsorption capacity for gas molecules. The spin-dependent
electronic transport of the g-C4N3/MoS2-based nanodevice is obviously regulated by parallel or anti-parallel
spin configuration in electrodes, leading to perfect single-spin conduction
behavior with a nearly 100% spin filtering efficiency, a negative
differential resistance effect, and other interesting electrical transport
phenomena. Moreover, g-C4N3/MoS2 exhibits
directional dependency and strong transport anisotropic behavior under
bias windows, indicating that the electric current propagates more
easily through the vertical direction than the horizontal direction.
The physical mechanisms are revealed and analyzed by presenting the
bias-dependent transmission spectra in combination with the projected
local device density of states. Finally, the g-C4N3/MoS2-based gas sensor is more sensitive to CO,
NO, NO2, and NH3 molecules with the chemisorption
type. The strong chemical adsorption leads to the formation of electrons
on the local scattering center and ultimately affects the transport
properties, resulting in the maximum gas sensitivity reaching 6.45
for NO at the bias of 0.8 V. This work not only reveals that the g-C4N3/MoS2 vdW heterostructure with high
anisotropy, perfect spin filtering, and outstanding gas sensitivity
is a promising 2D material but also provides an insight into the further
application in futuristic electronic nanodevices.
Recently, the successful synthesis of biphenylene network (BPN) monolayers (Matetskiy et al., 2021) has made significant progress in the study of carbon materials. Inspired by this material, the electronic structures,...
Recently, Dirac material BeN4 has been synthesized by using laser-heated diamond anvil-groove technology (Bykov et al 2021 Phys. Rev. Lett.
126 175501). BeN4 layer, i.e. beryllonitrene, represents a qualitatively class of two-dimensional (2D) materials that can be built of a metal atom and polymeric nitrogen chains, and hosts anisotropic Dirac fermions. Enlighten by this discovered material, we study the electronic structure, anisotropic transport properties and gas sensitivity of 2D BeN4 using the density functional theory combined with non-equilibrium Green’s function method. The results manifest that the 2D BeN4 shows a typical semi-metallic property. The electronic transport properties of the intrinsic BeN4 devices show a strong anisotropic behavior since electrons transmitting along the armchair direction is much easier than that along the zigzag direction. It directly results in an obvious switching characteristic with the switching ratio up to 105. Then the adsorption characteristics indicate that H2S, CO, CO2 and H2 molecules are physisorption, while the NH3, NO, NO2, SO2 molecules are chemisorption. Among these chemisorption cases, the 2D gas sensor devices show an extremely high response for SO2 recognition, and the high anisotropy of the original 2D BeN4 device still maintains after adsorbing gas molecules. Finally, high switching ratio and inorganic gas sensing performance of BeN4 monolayer could be clearly understood with local density of states, bias-dependent spectra, scattered state distribution. In general, the results indicate that the designed BeN4 devices have potential practical application in high-ratio switching devices and high gas-sensing molecular devices.
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