Evolution of subcritical nuclei in nitrogen-alloyed Ge2Sb 2Te5

Kristof Darmawikarta, Simone Raoux, Pierre Tchoulfian, Tian Li, John R. Abelson, Stephen G. Bishop

Research output: Contribution to journalArticlepeer-review


We analyze the evolution of subcritical nuclei as a function of nitrogen alloying and thermal annealing in the amorphous phase change material Ge 2Sb2Te5. The existence of subcritical nuclei is inferred through measurement of the nucleation time in pulsed laser annealing, and is detected more directly using fluctuation transmission electron microscopy measurements that are sensitive to topological order on the nanoscale. In samples that are pre-annealed before crystallization experiments, the nanoscale order consistently increases and the nucleation times consistently decrease, in agreement with the interpretation that the nanoscale order corresponds to a population of subcritical nuclei that ripens upon annealing. However, this correlation is less obvious in as-deposited samples across a range of nitrogen contents: The quantity of nanoscale order diminishes only slightly with increased nitrogen alloying, whereas the nucleation times increase by nearly two orders of magnitude. We therefore interpret that nitrogen must affect either the critical size in order for a nucleus to be stable (the thermodynamics) or the rate at which nucleation and growth take place (the kinetics).

Original languageEnglish (US)
Article number124907
JournalJournal of Applied Physics
Issue number12
StatePublished - Dec 15 2012

ASJC Scopus subject areas

  • Physics and Astronomy(all)


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