Nanomaterials and Microsystems Group, Physics Department, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain.
Phys Rev Lett. 2011 Jul 8;107(2):025901. doi: 10.1103/PhysRevLett.107.025901. Epub 2011 Jul 7.
We report the thermodynamic measurement of the enthalpy released during the aging of supported films of a molecular glass former, toluene, at temperatures well below the glass transition temperature. By using microfabricated devices with very short equilibration times (below 1 s), we evidence a remarkable variation of the relaxation rate on decreasing film thickness from 100 nm down to a 7 nm thick film. Our results demonstrate that surface atoms are more efficient than bulk atoms in attaining low energy configurations within the potential energy landscape.
我们报告了在远低于玻璃化转变温度的温度下，对甲苯这种分子玻璃形成体的支撑膜老化过程中释放的焓的热力学测量。通过使用具有非常短平衡时间（低于 1 秒）的微制造器件，我们证明了在薄膜厚度从 100nm 降低到 7nm 厚的薄膜时，弛豫速率会发生显著变化。我们的结果表明，表面原子比体相原子更有效地在势能景观中达到低能量构型。
