Berlin 2015 – scientific programme

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DS: Fachverband Dünne Schichten

DS 36: Poster Session I

DS 36.72: Poster

Thursday, March 19, 2015, 09:30–12:00, Poster A

Infrared optical investigation of plasmonic excitations in finite atom wires on Si(111)-5x2-Au — •Fabian Hötzel, Christian Huck, and Annemarie Pucci — Kirchhoff-Institute for Physics, Heidelberg University, Heidelberg, Germany

Self-assembled gold atom wires on vicinal Si(111), resulting in the 5x2 reconstruction, are investigated by Fourier transform infrared spectroscopy in transmittance geometry. According to reflection high energy electron diffraction patterns the wires are oriented preferably along the step edges. Relative transmittance spectra show a broad, anisotropic absorption feature at 728 cm⁻¹ at room temperature which shifts to 822 cm⁻¹ upon cooling down to 20 K. The signal can be attributed to a localized plasmonic excitation, forming a standing wave due to the finite length of the wires, which enables optical detection. For that reason, a metal-to-insulator transition can be excluded for Si(111)-5x2-Au in this temperature range. The chain length is confined by structural defects [1,2] and domain boundaries [3]. For the fundamental plasmon mode the plasmon wavelength is twice the chain length which results in an average gold chain length of 67 nm. The spectral line shape can be described classically within the electrostatic approximation and yields reasonable results for electron scattering rate, plasma frequency and chain length distribution. This contribution is part of the DFG Research Unit FOR 1700.
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Zhang et al., J. Phys.: Condens. Matter 19, 486004, 2007