  Organic molecular crystals encompass a vast range of materials from
pharmaceuticals to organic optoelectronics and proteins to waxes in biological
and industrial settings. Crystal defects from grain boundaries to dislocations
are known to play key roles in mechanisms of growth and also in the functional
properties of molecular crystals. In contrast to the precise analysis of
individual defects in metals, ceramics, and inorganic semiconductors enabled by
electron microscopy, significantly greater ambiguity remains in the
experimental determination of individual dislocation character and slip systems
in molecular materials. In large part, nanoscale dislocation analysis in
molecular crystals has been hindered by the severely constrained electron
exposures required to avoid irreversibly degrading these crystals. Here, we
present a low-dose, single-exposure approach enabling nanometre-resolved
analysis of individual extended dislocations in molecular crystals. We
demonstrate the approach for a range of crystal types to reveal dislocation
character and operative slip systems unambiguously.
