How adsorbates alter the metallic behavior of quasi-1D electron systems of the Si(5 5 3)-Au surface

Abstract

The plasmonic signals of quasi-1D electron systems are a clear and direct measure of their metallic behavior. Due to the finite size of such systems in reality, plasmonic signals from a gold-induced superstructure on Si(5 5 3) can be studied with infrared spectroscopy. The infrared spectroscopic features have turned out to be extremely sensitive to adsorbates. Even without geometrical changes of the surface superstructure, the effects of doping, of the adsorbate induced electronic surface scattering, and of the electronic polarizability changes on top of the substrate surface give rise to measurable changes of the plasmonic signal. Especially strong changes of the plasmonic signal have been observed for gold, oxygen, and hydrogen exposure. The plasmonic resonance gradually disappears under these exposures, indicating the transion to an insulating behavior, which is in accordance with published results obtained from other experimental methods. For C 70 and, as shown here for the first time, TAPP-Br, the plasmonic signal almost retains its original intensity even up to coverages of many monolayers. For C 70 , the changes of the spectral shape, e.g. of electronic damping and of the resonance position, were also found to be marginal. On the other hand, TAPP-Br adsorption shifts the plasmonic resonance to higher frequencies and strongly increases the electronic damping. Given the dispersion relation for plasmonic resonances of 1D electron systems, the findings for TAPP-Br indicate a push-back effect and therefore stronger confinement of the free charge carriers in the quasi-one-dimensonal channel due to the coverage by the flat TAPP-Br molecules. On the gold-doped Si(5 5 3)-Au surface TAPP-Br acts as counter dopant and increases the plasmonic signal.

Plasmon Standing Waves by Oxidation of Si(553)–Au

“…The spectral shape, especially the plasmonic resonance position of the HCW wires was investigated by fitting the data according to ref. 25 With this assumption we identify the energy of the IR absorption minima with the energy of the ground state of a plasmon standing wave on wires with an average length l. This wavelength cannot be exceeded at a given oxygen concentration so that no dispersion is possible for smaller k . Therefore, we took the energies of the IR absorption minima and determined the corresponding k value as the intersection of a non-dispersing state of this energy Figure 5: Relative transmittance spectra of clean and oxidized Au-Si(553) surfaces for the HCW phase.…”

“…24 Because of finite wire lengths, the plasmon resonance becomes optically detectable due to the dipolar character of excitations. 7,25 It is thus a very valuable tool for complementing our HREELS study that is also important to discriminate between finite size effects of wire lengths and possible adsorbate induced band gap opening.…”

Adsorbate‐Induced Modifications in the Optical Response of the Si(553)–Au Surface

“…Since then, numerous lines of research have emerged, dedicated to the investigation of the atomic structure, [ 18–21 ] lattice dynamics, [ 22 ] spin patterns, [ 23–25 ] phase transitions, [ 26,27 ] as well as electronic structure and its adsorption‐induced modifications. [ 28–32 ]…”

“…Since then, numerous lines of research have emerged, dedicated to the investigation of the atomic structure, [18][19][20][21] lattice dynamics, [22] spin patterns, [23][24][25] phase transitions, [26,27] as well as electronic structure and its adsorptioninduced modifications. [28][29][30][31][32] According to our current knowledge of the system, the hightemperature phase of the Si(553)-Au surface is stable from room temperature down to about 120 K. It consists of a double Au…”

Deposition-Dependent Morphology and Infrared Vibrational Spectra of Brominated Tetraazaperopyrene Layers

“…Starting from 1,3,8,10-tetraazaperopyrenes, a wide range of compounds have been successfully synthesized, but particularly, halogenation of the aromatic core was found to be promising to systematically tune their properties at a molecular level. , Therefore, they are promising candidates for future application in organic electronics as n-channel semiconductors. In this paper, we refer to previous work which was partly dealing with the arrangement of TAPP molecules on surfaces, ,, in which the behavior of the molecules at surfaces for monolayer (ML) up to multilayer coverage had been investigated. It was found that the molecules adsorbed preferably flat on the surface, which increases the substrate to adsorbate interaction.…”