Electronic and effective mass modulation in 2D BCN by strain engineering

Selective sensing properties and enhanced ferromagnetism in CrI3monolayer via gas adsorption

Recent fabrication of chromium triiodide (CrI₃) monolayers has raised potential prospects of developing two-dimensional (2D) ferromagnetic materials for spintronic device applications. The low Curie temperature has stimulated further interest for improving the ferromagnetic stability of CrI₃monolayer. Here, based on density functional theory calculations, we investigated the adsorption energy, charge transfer, electronic and magnetic properties of gases (CO, CO₂, N₂, NH₃, NO, NO₂, O₂, and SO₂) adsorption on the CrI₃monolayer. It is found that CrI₃is sensitive to the NH₃, NO, and NO₂adsorption due to the high adsorption energy and large charge transfer. The electrical transport results show that the conductivity of CrI₃monolayer is significantly reduced with the adsorption of N-based gases, suggesting that CrI₃exhibits superior sensitivity and selectivity toward N-based gases. In addition, the ferromagnetic stability and Curie temperature (T_C) of CrI₃monolayer can be effectively enhanced by the adsorption of magnetic gases (NO, NO₂, O₂). This work not only demonstrates that CrI₃monolayer can be used as a promising candidate for gas sensing, but also brings further interest to tune the electronic and magnetic properties of 2D ferromagnetic materials via gas adsorption.

Hybrid MXene-Graphene/Hexagonal Boron Nitride Structures: Electronic and Molecular Adsorption Properties

Recent advances in experimental techniques allow for the fabrication of hybrid structures. Here, we study the electronic and molecular adsorption properties of the graphene (G)/hexagonal boron nitride (h-BN)-MXenes (Mo2C) hybrid nanosheets. We use first-principles calculations to explore the structure and electronic properties of the hybrid structures of G-2H-Mo2C and h-BN-2H-Mo2C with two different oxygen terminations of the Mo2C surface. The embedding of G or h-BN patches creates structural defects at the patch-Mo2C border and adds new states in the vicinity of the Fermi energy. Since this can be utilized for molecular adsorption and/or sensing, we investigate the ability of the G-M-O1 and BN-M-O1 hybrid structures to adsorb twelve molecules. Generally, the adsorption on the hybrid systems is significantly higher than on the pristine systems, except for N2 and H2, which are weakly adsorbed on all systems. We find that OH, NO, NO2, and SO2 are chemisorbed on the hybrid systems. COOH may be chemisorbed, or it may dissociate depending on its location at the edge between the G/h-BN and the MXene. NH3 is chemisorbed/physisorbed on the BN/G-M-O1 systems. CO, H2S, CO2, and CH4 are physisorbed on the hybrid systems. Our results indicate that the studied hybrid systems can be used for molecular filtration/sensing and catalysis.

Tunable electronic properties and enhanced ferromagnetism in Cr2Ge2Te6monolayer by strain engineering

Recently, as a new representative of Heisenberg's two-dimensional (2D) ferromagnetic materials, 2D Cr₂Ge₂Te₆(CGT), has attracted much attention due to its intrinsic ferromagnetism. Unfortunately, the Curie temperature (T_C) of CGT monolayer is only 22 K, which greatly hampers the development of the applications based on the CGT materials. Herein, by means of density functional theory computations, we explored the electronic and magnetic properties of CGT monolayer under the applied strain. It is demonstrated that the band gap of CGT monolayer can be remarkably modulated by applying the tensile strain, which first increases and then decreases with the increase of tensile strain. In addition, the strain can increase the Curie temperature and magnetic moment, and thus largely enhance the ferromagnetism of CGT monolayer. Notably, the obvious enhancement ofT_Cby 191% can be achieved at 10% strain. These results demonstrate that strain engineering can not only tune the electronic properties, but also provide a promising avenue to improve the ferromagnetism of CGT monolayer. The remarkable electronic and magnetic response to biaxial strain can also facilitate the development of CGT-based spin devices.

Enhancing Ferromagnetism and Tuning Electronic Properties of CrI3 Monolayers by Adsorption of Transition-Metal Atoms

Among first experimentally discovered two-dimensional (2D) ferromagnetic materials, chromium triiodide (CrI₃) monolayers have attracted particular attention due to their potential applications in electronics and spintronics. However, the Curie temperature T_c of the CrI₃ monolayer is below room temperature, which greatly limits practical development of the devices. Herein, using density functional theory calculation, we explore how the electronic and magnetic properties of CrI₃ monolayers change upon adsorption of 3d transition-metal (TM) atoms (from Sc to Zn). Our results indicate that the electronic properties of the TM-CrI₃ system can be tuned from semiconductor to metal/half-metal/spin gapless semiconductor depending on the choice of the adsorbed TM atoms. Moreover, the adsorption can improve the ferromagnetic stability of CrI₃ monolayers by increasing both magnetic moments and T_c. Notably, T_c of CrI₃ with Sc and V adatoms can be increased by nearly a factor of 3. We suggest postsynthesis doping of 2D CrI₃ by deposition of TM atoms as a new route toward potential applications of TM-CrI₃ systems in nanoelectronic and spintronic devices.