Balberg Isaac
The Racah Institute of Physics, The Hebrew University, Jerusalem 9190401, Israel.
Nanomaterials (Basel). 2024 Mar 5;14(5):471. doi: 10.3390/nano14050471.
Glassy behavior is manifested by three time-dependent characteristics of a dynamic physical property. Such behaviors have been found in the electrical conductivity transients of various disordered systems, but the mechanisms that yield the glassy behavior are still under intensive debate. The focus of the present work is on the effect of the quantum confinement (QC) and the Coulomb blockade (CB) effects on the experimentally observed glassy-like behavior in semiconductor nanomaterials. Correspondingly, we studied the transient electrical currents in semiconductor systems that contain CdSe or Si nanosize crystallites, as a function of that size and the ambient temperature. In particular, in contrast to the more commonly studied post-excitation behavior in electronic glassy systems, we have also examined the current transients during the excitation. This has enabled us to show that the glassy behavior is a result of the nanosize nature of the studied systems and thus to conclude that the observed characteristics are sensitive to the above effects. Following this and the temperature dependence of the transients, we derived a more detailed macroscopic and microscopic understanding of the corresponding transport mechanisms and their glassy manifestations. We concluded that the observed electrical transients must be explained not only by the commonly suggested principle of the minimization of energy upon the approach to equilibrium, as in the mechanical (say, viscose) glass, but also by the principle of minimal energy dissipation by the electrical current which determines the percolation network of the electrical conductivity. We further suggest that the deep reason for the glassy-like behavior that is observed in the electrical transients of the nanomaterials studied is the close similarity between the localization range of electrons due to the Coulomb blockade and the caging range of the uncharged atomic-size particles in the classical mechanical glass. These considerations are expected to be useful for the understanding and planning of semiconductor nanodevices such as corresponding quantum dot memories and quantum well MOSFETs.
玻璃态行为由动态物理性质的三个随时间变化的特征表现出来。这种行为已在各种无序系统的电导率瞬变中被发现，但产生玻璃态行为的机制仍在激烈争论中。目前工作的重点是量子限制（QC）和库仑阻塞（CB）效应对半导体纳米材料中实验观察到的类玻璃态行为的影响。相应地，我们研究了包含CdSe或Si纳米微晶的半导体系统中的瞬态电流，作为尺寸和环境温度的函数。特别是，与电子玻璃态系统中更常研究的激发后行为不同，我们还研究了激发过程中的电流瞬变。这使我们能够表明玻璃态行为是所研究系统纳米尺寸性质的结果，从而得出观察到的特征对上述效应敏感的结论。基于此以及瞬变的温度依赖性，我们对相应的输运机制及其玻璃态表现有了更详细的宏观和微观理解。我们得出结论，观察到的电瞬变不仅必须像在机械（例如粘性）玻璃中那样，通过接近平衡时能量最小化这一通常提出的原理来解释，还必须通过决定电导率渗流网络的电流最小能量耗散原理来解释。我们进一步认为，在所研究的纳米材料电瞬变中观察到的类玻璃态行为的深层原因是由于库仑阻塞导致的电子局域化范围与经典机械玻璃中不带电原子尺寸粒子的笼化范围之间的密切相似性。这些考虑预计将有助于理解和规划诸如相应量子点存储器和量子阱MOSFET等半导体纳米器件。
