AVS 54th International Symposium
    Surface Science Tuesday Sessions
       Session SS-TuP

Paper SS-TuP5
Illuminating Analysis of Observed Low-Dimensional Plasmons in an Array of Metallic Quantum Wires

Tuesday, October 16, 2007, 6:00 pm, Room 4C

Session: Surface Science Poster Session
Presenter: T. Inaoka, Iwate University, Japan
Authors: T. Inaoka, Iwate University, Japan
T. Nagao, National Inst. for Materials Sci., Japan
Correspondent: Click to Email

Using self-assembly of adsorbed Au atoms on vicinal surfaces of Si(111) with regular step rows, one can form a regular array of Au atom chains at interval of 1.91 nm on a Si(557) surface. Each atom chain of alternating Au and Si atoms embedded in the topmost Si layer of the terrace creates a one-dimensional (1D) surface-state band of metallic character. Conduction electrons in this band are confined in a narrow region one-atom wide. This array of metallic quantum wires sustains low-dimensional plasmons (PL’s), namely, 1D PL’s interacting with one another, and strong 1D confinement enhances the exchange-correlation (XC) effect on the PL’s. In our previous work, by means of electron energy-loss spectroscopy (EELS) with a high wave-number resolution, we measured the low-dimensional PL’s in the quantum-wire array.1 In the present work, taking account of the interwire interaction and the XC effect, we investigate the dynamical response of the wire array to a probe electron in EELS. To consider the XC effect, we apply a self-consistent local-field-correction (LFC) theory to the wire array.2 Although the interwire interaction is so significant as to produce a considerable distribution of the PL-mode energy, the calculated PL energy dispersion in EELS agrees with the dispersion of a single isolated wire. This paradox can be ascribed to the fact that the external potential generated by the probe electron is localized so sharply as to act and to produce substantial induced charges only on one or two wires. The calculated dispersion gives a complete explanation of the observed sound-wave character. By comparing the results of the LFC calculation with those of the Random-phase-approximation calculation, we evaluate the XC effect. This effect is found to operate to lower the PL energy and to heighten the energy-loss intensity in EELS. Our analysis can reproduce quantitatively the observed energy dispersion and energy-loss intensity.

1T. Nagao, S. Yaginuma, T. Inaoka, and T. Sakurai, Phys. Rev. Lett. 97, 116802 (2006).
2T. Inaoka and T. Nagao, Mater. Trans., JIM, 48, 718 (2007).