Rational Surface Modification of Two-Dimensional Layered Black Phosphorus: Insights from First-Principles...

Surface modification of atomically thin semiconductors enables their electronic, optical, chemical, and mechanical properties to be tailored and allows these nanosheets to be processed in solutions. Here, we report first-principles density functional theory calculations, through which we show chemical functionalization of black phosphorus using phenyl, phenolate, and nitrene species, which were widely investigated for carbon-based materials. We find that covalent functionalization using nitrene-derived species introduces a strong P-N dative bond at the interface without perturbing its intrinsic electronic structure. The Lewis basic and nucleophilic P atom attacks, through a free pair of electrons, the Lewis acidic nitrene species. These results are further compared to other nitrene-derived functional groups on black phosphorus, including N-methylbenzene, N-aminobenzene, and N-nitrobenzene. We find that by tuning the charge redistribution at the interface, the work function of black phosphorus can be tuned by more than 2 eV. These results suggest valuable tunability of the electronic properties of two-dimensional layered black phosphorus by covalent functionalization for future device applications.