  The unique optoelectronic properties of black phosphorus (BP) have triggered
great interest in its applications in areas not fulfilled by other layered
materials (LMs). However, its poor stability (fast degradation, i.e. <<1 h for
monolayers) under ambient conditions restricts its practical application. We
demonstrate here, by an experimental-theoretical approach, that the
incorporation of nitrogen molecules (N2) into the BP structure results in a
relevant improvement of its stability in air, up to 8 days without optical
degradation signs. Our strategy involves the generation of defects (phosphorus
vacancies) by electron-beam irradiation, followed by their healing with N2
molecules. As an additional route, N2 plasma treatment is presented as an
alternative for large area application. Our first principles calculations
elucidate the mechanisms involved in the nitrogen incorporation as well as on
the stabilization of the modified BP, which corroborates with our experimental
observations. This stabilization approach can be applied in the processing of
BP, allowing for its use in environmentally stable van der Waals
heterostructures with other LMs as well as in optoelectronic and wearable
devices.
