Localization, splitting, and mixing of field emission resonances induced by alkali metal clusters on Cu(100)
Localization, splitting, and mixing of field emission resonances induced by alkali metal clusters on Cu(100)
复制标题
DOI：
10.1103/physrevb.83.115101
复制
发表时间：
2011-03-02
影响因子：
3.7
通讯作者：
Arnau, A.
中科院分区：
文献类型：
--
作者：
Stepanow, S.;Mugarza, A.;Arnau, A.
本文报道了用扫描隧道显微镜（STM）和理论波包传播方法对沉积在Cu（100）表面上的纳米碱金属团簇的场发射共振（FER）进行的联合研究。除了原始Cu（100）表面的FER之外，我们还观察到岛诱导共振的出现，所述岛诱导共振对于与衬底的投影带隙内的电子能量相对应的STM偏置电压值特别好地解决。相应的dI/dV图揭示了不同性质的岛诱导共振。它们的电子密度分布在碱金属团簇内部或团簇边界。我们的模型计算使我们能够解释的实验结果，由于两种岛诱导态的共存和混合。一方面，由于碱金属的功函数低于衬底的功函数，因此纳米尺寸的碱金属簇引入了钉扎到簇上方的真空能级的本征局域电子态。这些状态可以被看作是由簇边界量子化的完整碱金属覆盖层的FER。另一方面，由于碱金属簇的吸引势阱导致Cu（100）表面的FER的二维（2D）局部化，相应的共振分裂分量出现在母连续体的底部下方。我们的主要结论是基于有吸引力的性质的碱性广告岛潜力。它们是普遍有效的，因此，重要的是要了解在二维电子约束。
We report on a joint scanning tunneling microscopy (STM) and theoretical wave packet propagation study of field emission resonances (FER's) of nanosized alkali metal clusters deposited on a Cu(100) surface. In addition to FER's of the pristine Cu(100) surface, we observe the appearance of island-induced resonances that are particularly well resolved for STM bias voltage values corresponding to electron energies inside the projected band gap of the substrate. The corresponding dI/dV maps reveal island-induced resonances of different nature. Their electronic densities are localized either inside the alkali cluster or on its boundaries. Our model calculations allow us to explain the experimental results as due to the coexistence and mixing of two kinds of island-induced states. On the one side, since the alkali work function is lower than that of the substrate, the nanosized alkali metal clusters introduce intrinsic localized electronic states pinned to the vacuum level above the cluster. These states can be seen as the FER's of the complete alkali overlayer quantized by the cluster boundaries. On the other side, the attractive potential well due to the alkali metal cluster leads to two-dimensional (2D) localization of the FER's of the Cu(100) surface, the corresponding split component of the resonances appearing below the bottom of the parent continuum. Our main conclusions are based on the attractive nature of the alkali ad-island potential. They are of general validity and, therefore, significant to understand electron confinement in 2D.