Nanocrystal transformations observed

July 11, 2011
Fast Fourier

Fast Fourier transform pattern (left) and high-resolution TEM images of the low-chalcocite (green) and high-chalcocite (red) domains in a copper sulfide nanocrytal (credit: Berkeley Lab)

The first direct observation of structural transformations within a copper sulfide nanocrystal, a semiconductor expected to play an important role in future energy technologies, has been reported by researchers at the DOE’s Lawrence Berkeley National Laboratory (Berkeley Lab).

According to phase transition theory, a solid crystal will fluctuate between two equilibrium structures near the phase transition point before reaching a stable configuration. To test this theory, the researchers used TEAM 0.5, one of the world’s most powerful transmission electron microscopes, to zap the crystal with an electron beam, and observed structural fluctuations in the nanocrystal as it transitioned between low- and high-chalcocite solid-state phases.

These fluctuations are highly relevant to understanding such phenomena as how ion transport occurs within electrodes during charging and discharging batteries, or how the structures of a solid material might change at the interface between an electrode and an electrolyte.

Ref.: A. Paul Alivisatos, et al., Observation of Transient Structural-Transformation Dynamics in a Cu2S Nanorod, Science, July 2011: Vol. 333 no. 6039 pp. 206-209 [DOI: 10.1126/science.1204713]