  Using first-principles atomistic simulations, we study the response of
atomically-thin layers of transition metal dichalcogenides (TMDs) - a new class
of two-dimensional inorganic materials with unique electronic properties - to
electron irradiation. We calculate displacement threshold energies for atoms in
21 different compounds and estimate the corresponding electron energies
required to produce defects. For a representative structure of MoS2, we carry
out high-resolution transmission electron microscopy experiments and validate
our theoretical predictions via observations of vacancy formation under
exposure to a 80 keV electron beam. We further show that TMDs can be doped by
filling the vacancies created by the electron beam with impurity atoms.
Thereby, our results not only shed light on the radiation response of a system
with reduced dimensionality, but also suggest new ways for engineering the
electronic structure of TMDs.
