Electronic transport in quasi-1D atomic wires

Atomic wires grown by self-assembly are prototype 1D systems for studying fundamental aspects, e.g. CDW, Peierls instabilities or the dimensional crossover from a Fermi to a Luttinger liquid behavior. In addition, the peculiar interactions between charge, spin and lattice could lead to interesting potential applications in future nanoelectronic devices. In this thesis, three highly discussed atomic wire systems are analyzed by means of a 4pp STM/SEM system. The first part of the thesis treats the In/Si(111)-(4 × 1) reconstruction which serves as a benchmark system for the understanding of 1D atomic chain reconstructions. It shows strong anisotropic transport properties and a temperature driven MIT. Although being intensively studied for two decades, there are still open questions, like the effect of defects induced by adsorption (e.g. oxygen) in respect to the MIT. It turns out that the sensitivity toward defects can be increased by one order of magnitude by performing the transport experiments on confined areas. Moreover, oxygen adsorption dependent transport studies not only show a reduction of conductivity along the direction of atomic chains but show also a decrease in the perpendicular direction. This was not reported before and reveals an effective interwire coupling between the chains in agreement with additional DFT calculations. The second part of the thesis focuses on Au-induced wire structures on Si(hhk) substrates. Those attracted recently a lot of attention because of their pronounced magnetic order, which mimics a 2D quantum spin liquid state. The Si(553)-Au and Si(557)-Au surfaces are carefully analyzed during in-situ adsorption of molecular oxygen. In combination with LEED and DFT calculations, the transport in terms of the different structural building blocks (Au chains, Siadatom chain, Si-HC edge) is discussed. It is shown, that the cause for the metallic surface bands along the wires are of different origin. Therefore, while the Si(553)-Au surface turns out to be rather immune against oxidation, the Si(557)-Au surface reveals a strong decrease of the conductance due to complete destruction of the Si-adatom ordering along the chains. In addition, the MIT of these systems is investigated. Here, a special focus is set on the Si(553)Au reconstruction. Within a LEED study it is shown that the ×3 periodicity undergoes structural transition at TC = 100 K, i.e. the ×3 periodicity along the wires vanishes. In contrast, the transport data reveals a residual conductivity along the wires below TC ruling out a MIT associated with the phase transition of the ×3 reconstruction. The last part of the thesis analyzes the transport properties of TbSi2 nanowires grown on vicinal Si(001) substrates. These rare-earth silicide nanowires could generally be very promising for further downscaling of Si based interconnects in CMOS technology because the wires can be grown several micrometer long while they are extremely thin with nanometer widths. A combined STM and transport study shows that the resistivity is strongly depending on the height of wires, which is increased for small heights. The data can be described by a theoretical quasi-classical model considering the surface roughness and lateral surface correlation.