  Black phosphorus is a monoatomic semiconducting layered material that
degrades exothermically in the presence of light and ambient contaminants. Its
degradation dynamics remain largely unknown. Even before degradation,
local-probe studies indicate non-negligible local curvature --through a
non-constant height distribution-- due to the unavoidable presence of intrinsic
defects. We establish that these intrinsic defects are photo-oxidation sites
because they lower the chemisorption barrier of ideal black phosphorus (> 10 eV
and out of visible-range light excitations) right into the visible and
ultra-violet range (1.6 to 6.8 eV), thus enabling photo-induced oxidation and
dissociation of oxygen dimers. A full characterization of the material's shape
and of its electronic properties at the early stages of the oxidation process
is presented as well. This study thus provides fundamental insights into the
degradation dynamics of this novel layered material.

Materials Science