In situ observation of fast surface dynamics during the vapor-deposition of a stable organic glass
In situ observation of fast surface dynamics during the vapor-deposition of a stable organic glass
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稳定有机玻璃气相沉积过程中快速表面动力学的原位观察
DOI：
10.1039/d0sm01916j
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发表时间：
2020
期刊：
影响因子：
3.4
通讯作者：
Richert, R.
中科院分区：
文献类型：
--
作者：
Thoms, E.;Gabriel, J. P.;Guiseppi-Elie, A.;Ediger, M. D.;Richert, R.
通过测量分子玻璃成型体的 110 nm 薄膜物理气相沉积过程中介电电容 (ΔC) 和耗散 (Δtan δ) 的增量，我们提供了移动表面层的直接证据，该表面层导致了气相沉积玻璃的非凡性能。以 0.1 nm s−1 的速率在 Tdep = 75 K = 0.82Tg 下沉积到基板上，我们观察到 2.5 nm 厚的表面层，平均弛豫时间为 0.1 s，而下面生长的玻璃具有较高的动力学稳定性。沉积过程终止后，Δtan δ 的水平持续下降数千秒，表明表面附近的堆积密度出现缓慢的老化式增加。在非常低的沉积温度（32 和 42 K）下，表面层厚度和迁移率以及动力学稳定性都会降低。
By measuring the increments of dielectric capacitance (ΔC) and dissipation (Δtan δ) during physical vapor deposition of a 110 nm film of a molecular glass former, we provide direct evidence of the mobile surface layer that is made responsible for the extraordinary properties of vapor deposited glasses. Depositing at a rate of 0.1 nm s−1 onto a substrate at Tdep = 75 K = 0.82Tg, we observe a 2.5 nm thick surface layer with an average relaxation time of 0.1 s, while the glass growing underneath has a high kinetic stability. The level of Δtan δ continues to decrease for thousands of seconds after terminating the deposition process, indicating a slow aging-like increase in packing density near the surface. At very low deposition temperatures, 32 and 42 K, the surface layer thicknesses and mobilities are reduced, as are the kinetic stabilities.