  Studying the atomic structure of intrinsic defects in two-dimensional
transition metal dichalcogenides is difficult since they damage quickly under
the intense electron irradiation in transmission electron microscopy (TEM).
However, this can also lead to insights into the creation of defects and their
atom-scale dynamics. We first show that MoTe 2 monolayers without protection
indeed quickly degrade during scanning TEM (STEM) imaging, and discuss the
observed atomic-level dynamics, including a transformation from the 1H phase
into 1T', three-fold rotationally symmetric defects, and the migration of line
defects between two 1H grains with a 60{\deg} misorientation. We then analyze
the atomic structure of MoTe2 encapsulated between two graphene sheets to
mitigate damage, finding the as-prepared material to contain an unexpectedly
large concentration of defects. These include similar point defects (or quantum
dots, QDs) as those created in the non-encapsulated material, and two different
types of line defects (or quantum wires, QWs) that can be transformed from one
to the other under electron irradiation. Our density functional theory
simulations indicate that the QDs and QWs embedded in MoTe2 introduce new
midgap states into the semiconducting material, and may thus be used to control
its electronic and optical properties. Finally, the edge of the encapsulated
material appears amorphous, possibly due to the pressure caused by the
encapsulation.
