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首页> 外文期刊>The Journal of Chemical Physics >Long-range correlated dynamics in ultra-thin molecular glass films
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Long-range correlated dynamics in ultra-thin molecular glass films

机译：超薄分子玻璃膜中的远程相关动力学

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摘要

It has been previously shown that the free surface of molecular glasses has enhanced surface diffusion compared to the bulk. However, the degree by which the glass dynamics are affected by the free surface remains unexplored. Here, we measure enhanced dynamics in ultra-thin molecular glass films as a function of film thickness. We demonstrate that these films exhibit a sharp transition from glassy solid to liquid-like behavior when the thickness is reduced below 30 nm. This liquid-like behavior persists even at temperatures well below the glass transition temperature, T-g. The enhanced dynamics in these films can produce large scale morphological features during physical vapor deposition and lead to a dewetting instability in films held at temperatures as low as T-g - 35 K. The effective viscosity of these films are measured by monitoring the dewetting kinetics. These measurements combined with cooling-rate dependent T-g measurements show that the apparent activation barrier for rearrangement decreases sharply in films thinner than 30 nm. This sharp transition in the dynamics suggests that long-range correlated dynamics exists in these films such that the enhancement induced by the free surface can strongly affect the dynamics of the film over a length scale that is ten times larger than the size of the molecules. Published by AIP Publishing.
机译：先前已经表明，与散装相比，分子玻璃的自由表面具有增强的表面扩散。然而，玻璃动态受自由表面影响的程度仍未探索。这里，我们测量超薄分子玻璃膜中的增强动力学作为膜厚度的函数。我们证明，当厚度降低30nm时，这些薄膜表现出从玻璃状固体到液体状行为的急剧过渡。这种液体样行为甚至仍然在低于玻璃化转变温度，T-G的温度下持续存在。这些薄膜中的增强动力学可以在物理气相沉积期间产生大规模的形态特征，并导致在低至T-G - 35K的温度下保持的薄膜中的脱模不稳定性。通过监测脱水动力学来测量这些膜的有效粘度。这些测量与冷却速率相关的T-G测量相结合，表明重新排列的表观激活屏障在薄于30nm的薄膜中急剧下降。动态中的这种急剧转变表明，这些薄膜中存在远程相关动态，使得由自由表面引起的增强能够强烈地影响膜的动态，其长度尺度大于分子尺寸的十倍。通过AIP发布发布。

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