Impurity properties in phosphorene: First-principles calculations and comparisons

Abstract

Based on first-principles calculations within the generalized gradient approximation (GGA) and the hybrid functional (HSE06) frameworks, the properties of dozens of impurities in phosphorene have been systematically investigated and compared. The adsorbed Li, Na and K impurities have low formation energies and create defect states near the conduction band minimum of phosphorene, thus they are promising donors. The adsorbed Ga, In, Cu and Ag impurities also act as donors but have high formation energies, making them hard to be formed in equilibrium conditions. Group-II and group-VIII impurities introduce defect states in the energy gap far away from the band edges, while the adsorbed Zn, Cd and group-VI impurities produce no defect states in the gap region. According to the GGA results, the substitutional group-IV impurities create defect states near the valence band maximum, but in the HSE06 calculations these states shift deeply into the energy gap, rendering the impurities hard to be activated. Among the group-VI and group-VII impurities, only the adsorbed O, F and Cl have low formation energy. The formation energy of the same group impurities monotonously decreases or increases with the impurity-atom’s location in the periodic table of elements.