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

Beryllium tetrazolium nitride (BeN 4 ) 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 MN 4 (M = Be, Mg and Ga) monolayers and their gas sensing properties towards nitride -gases (NH 3 , NO 2 , NO). The obtained results show that BeN 4 exhibits semimetallic properties, MgN 4 is a semiconductor with a bandgap of 0.13 eV, and the GaN 4 monolayer presents strong metallic properties. Interestingly, the BeN 4 and MgN 4 monolayers are found to have anisotropic Dirac cones. The MN 4 -based 2D devices all exhibit excellent conductance as well as strong anisotropic transport, with maximum switching ratios of 10 7 and 10 4 for MgN 4 and BeN 4 , respectively. The adsorption properties indicate that the adsorption of NH 3 , NO 2 , and NO molecules on MN 4 monolayers are all chemisorptions, with the system owning much larger adsorption energies and bader charge transfers of the NO 2 and NO molecules than those for the NH 3 molecules, suggesting the MN 4 monolayer has strong selective adsorption and responsiveness to NO 2 and NO molecules. The designed gas sensor based on MgN 4 show good response characteristics for NO molecules, as evidenced by the maximum current changes before and after adsorption of 30.31 mu A, respectively. In summary, MN 4 (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.