High switching characteristics and sensing-performance improvement of two-dimensional MN4 (M = Be, Mg, Ga) monolayer based nanodevices

Abstract

Beryllium tetrazolium nitride (BeN4) has recently been synthesized under high pressure by laserheated diamond anvil electrodes as a new class of two-dimensional layered materials. Inspired by this, we perform first-principles calculations to investigate the electronic transport properties of MN4 (M = Be, Mg and Ga) monolayers and their gas sensing properties towards nitride-gases (NH3, NO2, NO). The obtained results show that BeN4 exhibits semi-metallic properties, MgN4 is a semiconductor with a bandgap of 0.13 eV, and the GaN4 monolayer presents strong metallic properties. Interestingly, the BeN4 and MgN4 monolayers are found to have anisotropic Dirac cones. The MN4-based 2D devices all exhibit excellent conductance as well as strong anisotropic transport, with maximum switching ratios of 107 and 104 for MgN4 and BeN4, respectively. The adsorption properties indicate that the adsorption of NH3, NO2, and NO molecules on MN4 monolayers are all chemisorptions, with the system owning much larger adsorption energies and bader charge transfers of the NO2 and NO molecules than those for the NH3 molecules, suggesting the MN4 monolayer has strong selective adsorption and responsiveness to NO2 and NO molecules. The designed gas sensor based on MgN4 show good response characteristics for NO molecules, as evidenced by the maximum current changes before and after adsorption of 30.31 µA, respectively. In summary, MN4 (M = Be, Mg and Ga) monolayers can be important candidates for high switching ratio devices and for the detection and trapping of toxic gas molecules NO.