Thursday, October 5th: ABC...z Seminar Series: Assessing nucleation theory under extreme conditions

Event Date: 

Thursday, October 5, 2017

Event Date Details: 

3:30pm - 4:30pm

Event Location: 

  • Broida Hall 1640
  • ABC...z Seminar Series

Nucleation is a core scientific principle describing the formation of new phases and materials. From the synthesis of electronic materials to the formation of clouds, classical nucleation theory is applied in wide-ranging fields. However, nucleation energy landscapes have never been directly measured, leaving the classical theory untested at the atomic level. We directly measured the diamond nucleation energy landscape during plasma-enhanced chemical vapor deposition (CVD) using a series of diamondoid molecules as atomically-defined proto-nuclei. Surprisingly, we find that diamond critical nuclei are 26 carbon atom clusters, and the measured nucleation barrier is more than four orders of magnitude smaller than previous estimations. These results resolve long-standing questions surrounding the prevalence of nucleation during the synthesis of several industrially important materials, including diamond and silicon, and indicate that nucleation barriers should be revisited for many vapor deposition processes. More broadly, we quantitatively confirm that the fundamental tenets of classical theory hold down to atomic scales, providing rigorous justification for applying classical theory in diverse contexts.

Matthew Gebbie, Stanford University