Tunable electronic, magnetic and optical properties by surface adsorption in monolayer CrI 3

The recent discovery of magnetism in ultrathin materials of van der Waals crystals has created profound interest due to their potential applications in electronics and spintronics. However, the low value of Curie temperature in recently discovered two-dimensional material CrI 3 limits their application in practical devices. Based on first-principles calculations, we have investigated the influence of surface adsorption by oxygen(O) and nitrogen(N) atoms on the electronic, magnetic and optical properties of monolayer (ML) CrI 3 . We find that adsorption maintains the indirect band gap semiconducting nature of CrI 3 but leads to a reduction in the gap. Magnetic anisotropy energy (MAE) calculations report a switching of the magnetic easy axis from the out-of-plane to the in-plane direction under O/N adsorption. However, a dramatic enhancement of Curie temperature above room temperature is observed only under N adsorption. We attribute such change in MAE to the doping effect induced by adsorption. The optical properties of CrI 3 reveal important information like widening of the effective energy range of absorption and lowering of the peak height under O/N adsorption. So, surface adsorption may be an effective way to tune properties and functionalities of CrI 3 monolayer and other low-dimensional materials.