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Low-Dimensional Electronic Excitations in a Metallic Monolayer of Finite Area Adsorbed on a Semiconductor Surface

半导体表面吸附的有限面积金属单层中的低维电子激发

基本信息

批准号：
13640315
负责人：
INAOKA Takeshi
金额：
$ 1.92万
依托单位：
Iwate University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2003
项目状态：
已结题

项目摘要

The Si(111)-√<3>×√<3> -Ag surface can be formed by depositing one monolayer of Ag atoms on a Si(111)-7×7 surface, and the surface-state band at this surface provides an ideal two-dimensional conduction-electron system (2DES). This electron system is confined in each √<3> ×√<3>-Ag domain surrounded by atomic steps or out-of-phase boundaries. Electronic excitations in this 2DES involves some interesting characteristics, such as low dimensionality, quantum-size effects, and presence of both edge and area excitations.First, we have investigated two-dimensional plasmons (PL's) in the metallic monolayer of infinite area. This investigation has shown that, owing to low dimensionality, the exchange-correlation effects begin to appear remarkably with an increase in PL wave number q, though the 2DES has a high effective density. Our calculation has given a virtually quantitative description of the experimental results of high-resolution electron energy-loss spectroscopy (HREELS).Next, by means o … More f the local-density approximation, we have examined low-dimensional PL's in a 2DES restricted to a strip region with constant width D and infinite length. We have found a series of PL dispersion branches where the node number increases one by one with ascending energy. Here, the node number is specified from the distribution of the induced electron density δn across the strip. The 0-node and 1-node modes are edge PL's with different parity in the δn distribution. With a decrease in D, the 0-node modes evolve into one-dimensional PL's. Each higher-order mode with more than one node has a standing-wave pattern in its δn distribution in a smaller q region, which evolves into area PL's with an increase in q. In a mode with more nodes, the standing-wave pattern persists up to a larger q range. As the width D becomes larger, the energy separation between neighboring PL dispersion branches becomes smaller, and the evolution into the area PL's occurs at smaller q values. Our analysis in relation to HREELS has shown that loss peaks due to a series of PL dispersion branches should appear clearly in the energy-loss spectrum, and that the loss peaks should have observable intensity, if a probe electron follows a trajectory in the vicinity of the strip region. Less

在Si（111<3><3>）-7 7表面上沉积单层Ag原子可以形成Si（111）-Ag × Ag-Ag表面，该表面的表面态带提供了理想的二维导电电子系统（2DES）。该电子系统被限制在每个<3><3>由原子台阶或异相边界包围的x-Ag域中。电子激发在这个2DES涉及一些有趣的特点，如低维，量子尺寸效应，并存在边缘和面积激发。首先，我们已经研究了二维等离子体激元（PL的）在无限大面积的金属单层。研究表明，尽管2DES具有很高的有效密度，但由于其低维性，随着PL波数q的增加，交换关联效应开始显著地出现。我们的计算给出了高分辨电子能量损失谱（HREELS）实验结果的定量描述。 ...更多信息在局域密度近似下，我们研究了限制在具有恒定宽度D和无限长的带状区域内的2DES中的低维PL。我们发现了一系列的PL色散分支，其中节点数随着能量的增加而逐个增加。在这里，节点数是由感应电子密度δn在整个条带上的分布来指定的。0-节点和1-节点模是在δn分布中具有不同奇偶性的边缘PL。随着D的减小，0节点模式演变为一维PL。每个具有多个节点的高阶模在其δn分布中在较小的q区域中具有驻波图案，该图案随着q的增加而演变成面积PL。在具有更多节点的模式中，驻波图案持续到更大的q范围。随着宽度D变得更大，相邻PL色散分支之间的能量分离变得更小，并且在更小的q值处发生到区域PL的演变。我们的分析与HREELS表明，由于一系列的PL色散分支的损失峰应该出现在能量损失谱中清楚，并且损失峰应该具有可观察到的强度，如果探测电子遵循在条带区域附近的轨迹。少