| 概 要 |
Direct atomically resolved observation of dynamics deep in the glassy regime has proved elusive for atomic and molecular glasses. Studies below the glass transition temperature Tg are especially rare due to long waiting times required to observe dynamics. I will present data directly visualizing surface glass dynamics deep in the glassy regime.
Analysis of scanning tunneling microscopy movies at the surface of semiconducting and metallic glasses, with time resolution as fast as 1 minute and extending up to 1,000 minutes., reveals that rearrangements of surface clusters occur almost exclusively by two-state hopping (P(3-state) ≈ 0.06). All clusters are compact structures with a width of 2-8 atomic spacings along the surface plane. The two-state dynamics is both spatially and temporally heterogeneous: we observe rate heterogeneity at individual sites and a broad distribution of rates at adjacent sites. We estimate an average activation free energy of 14 kBTg for surface clusters. The results are discussed in the context of current glass transition models.
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