Department of Chemistry, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina 27514, United States.
Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign , Champaign, Illinois 61820, United States.
Nano Lett. 2015 Oct 14;15(10):6429-33. doi: 10.1021/acs.nanolett.5b01707. Epub 2015 Sep 11.
The role of surface termination on phonon-mediated relaxation of an excited electron in quantum dots was investigated using first-principles simulations. The surface terminations of a silicon quantum dot with hydrogen and fluorine atoms lead to distinctively different relaxation behaviors, and the fluorine termination shows a nontrivial relaxation process. The quantum confined electronic states are significantly affected by the surface of the quantum dot, and we find that a particular electronic state dictates the relaxation behavior through its infrequent coupling to neighboring electronic states. Dynamical fluctuation of this electronic state results in a slow shuttling behavior within the manifold of unoccupied electronic states, controlling the overall dynamics of the excited electron with its characteristic frequency of this shuttling behavior. The present work revealed a unique role of surface termination, dictating the hot electron relaxation process in quantum-confined systems in the way that has not been considered previously.
本工作使用第一性原理模拟研究了表面终止对量子点中激发电子的声子介导弛豫的作用。具有氢和氟原子的硅量子点的表面终止导致明显不同的弛豫行为，而氟终止显示出非平凡的弛豫过程。量子限制的电子态受到量子点表面的显著影响，我们发现，通过其与相邻电子态的不频繁耦合，特定的电子态决定了弛豫行为。通过这种电子态的动态波动，在未占据电子态的子空间内产生缓慢的穿梭行为，通过该穿梭行为的特征频率控制激发电子的整体动力学。本工作揭示了表面终止的独特作用，以以前未考虑的方式控制量子受限系统中的热电子弛豫过程。
