Applied Physics Department and Centre for Nano Science and Nanotechnology, Hebrew University, Jerusalem91904, Israel.
Sci Rep. 2013;3:1845. doi: 10.1038/srep01845.
Many physical systems respond to slowly changing external force through avalanches spanning broad range of sizes. Some systems crackle even without apparent external force, such as bursts of neuronal activity or charge transfer avalanches in 2D molecular layers. Advanced development of theoretical models describing disorder-induced critical phenomena calls for experiments probing the dynamics upon tuneable disorder. Here we show that isomeric structural transitions in 2D organic self-assembled monolayer (SAM) exhibit critical dynamics with experimentally tuneable disorder. The system consists of field effect transistor coupled through SAM to illuminated semiconducting nanocrystals (NCs). Charges photoinduced in NCs are transferred through SAM to the transistor surface and modulate its conductivity. Avalanches of isomeric structural transitions are revealed by measuring the current noise I(t) of the transistor. Accumulated surface traps charges reduce dipole moments of the molecules, decrease their coupling, and thus decrease the critical disorder of the SAM enabling its tuning during experiments.
许多物理系统通过跨越广泛尺寸范围的雪崩对缓慢变化的外力做出响应。有些系统甚至在没有明显外力的情况下噼啪作响，例如神经元活动的爆发或二维分子层中的电荷转移雪崩。描述描述无序诱导的临界现象的理论模型的高级发展需要实验来探测可调谐无序时的动力学。在这里，我们表明二维有机自组装单层 (SAM) 的异构结构转变表现出具有实验可调谐无序的临界动力学。该系统由通过 SAM 耦合到被照明半导体纳米晶体 (NC) 的场效应晶体管组成。NC 中光致产生的电荷通过 SAM 转移到晶体管表面并调节其导电性。通过测量晶体管的电流噪声 I(t) 来揭示异构结构转变的雪崩。累积的表面陷阱电荷会降低分子的偶极矩，降低它们的耦合，从而降低 SAM 的临界无序，使其在实验过程中可以进行调节。
