Direct Observation of Charge-Density-Wave Discommensurations and Dislocations in2H-TaSe2

Discommensurations and dislocations in the incommensurate charge-density-wave structure of $2H$-Ta${\mathrm{Se}}_2$ have been observed directly by dark-field transmission electron microscopy with use of satellite reflections produced because of the phase transition. We have imaged the domain structure in the striped phase on warming above 92 K. Discommensurations are found to have a width ∼ 150 Å and their spacings vary in the expected manner with temperature.