论文标题
沉积金簇中辐射诱导的结构转化的机理
Mechanisms of radiation-induced structural transformations in deposited gold clusters
论文作者
论文摘要
在理论上和计算上研究了暴露于透射电子显微镜（TEM）电子束的沉积金属簇中结构转化的物理机制。尺寸选择的Au $ _ {923} $簇在碳底物上轻轻沉积的TEM实验表明，在暴露于200-Kev Electron Electon Beam时，这些簇经历了从Icosahedron到Decahedron到Decahedron和Face-Center Cubic（FCC）结构的结构转换。在本文中，我们证明了在沉积金属簇中形成的集体电子（等离子体）激发的松弛可以诱导实验观察到的结构转化。簇中的这种激发主要是由于与从底物发出的低能二级电子的相互作用。等离子体诱导的能量弛豫事件的特征发生时间比通过电力原代电子到簇原子的动量传递事件的数量级短几个数量级。分子动力学模拟补充了理论分析，该模拟表明，由于群集的振动激发，将二十面体Au $ _ {923} $簇软沉积在石墨上。
Physical mechanisms of structural transformations in deposited metallic clusters exposed to an electron beam of a transmission electron microscope (TEM) are studied theoretically and computationally. Recent TEM experiments with size-selected Au$_{923}$ clusters softly deposited on a carbon substrate showed that the clusters undergo structural transformations from icosahedron to decahedron and face-center cubic (fcc) structures upon exposure to a 200-keV electron beam. In this paper, we demonstrate that the relaxation of collective electronic (plasmon) excitations formed in deposited metal clusters can induce the experimentally observed structural transformations. Such excitations in the clusters are formed mainly due to the interaction with low-energy secondary electrons emitted from a substrate. The characteristic occurrence times for plasmon-induced energy relaxation events are several orders of magnitude shorter than those for the momentum transfer events by energetic primary electrons to atoms of the cluster. The theoretical analysis is complemented by molecular dynamics simulations, which show that an icosahedral Au$_{923}$ cluster softly deposited on graphite is transformed into an fcc-like structure due to the vibrational excitation of the cluster.
