Selective sensing properties and enhanced ferromagnetism in CrI₃ monolayer 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 CrI₃ monolayer. 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 CrI₃ monolayer. It is found that CrI₃ is sensitive to the NH₃, NO, and NO₂ adsorption due to the high adsorption energy and large charge transfer. The electrical transport results show that the conductivity of CrI₃ monolayer is significantly reduced with the adsorption of N-based gases, suggesting that CrI₃ exhibits superior sensitivity and selectivity toward N-based gases. In addition, the ferromagnetic stability and Curie temperature (T _C) of CrI₃ monolayer can be effectively enhanced by the adsorption of magnetic gases (NO, NO₂, O₂). This work not only demonstrates that CrI₃ monolayer 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.