Electronic instabilities and structural fluctuations in self-assembled atom wires

Electronic instabilities and structural fluctuations in self-assembled atom wires

Snijders, P.C.

Weitering, H.H. (promotor)
Klapwijk, T.M. (promotor)

Applied Sciences

2006-06-08

One-dimensional (1D) solid state systems can behave drastically different from their higher dimensional counterparts. Increased interactions can produce electronic and/or structural instabilities. In this respect, the following fundamental questions are important for a proper understanding of the properties of the ultimate 1D systems consisting of atom wires: Are atom wires created by self-assembly on silicon (Si) surfaces actually stable? Do atom wires exist that are metallic (at low temperatures)? What role is played by defects in these atom wires? This Thesis attempts to find an answer to these questions. Atom wires were realized by self-assembly on vicinal Si surfaces. Using Scanning Tunneling Microscopy and Spectroscopy combined with Density Functional Theory calculations, a full analysis of the (thermodynamic) stability of Gallium (Ga) atom wires on Si(112) has been made, including the energetics of fluctuating intrinsic structural defects. It is shown that the stable atom wires fully passivate the surface, and that the spacing between intrinsic quasi-1D meandering vacancy lines can be tuned continuously through experimental adjustment of the Ga chemical potential. Gold atom wires on the Si(553) surface show an incommensurate metallic state at room temperature. Decreasing the temperature, two competing charge density waves (CDW) within single atom wires are observed, accompanied by a third CDW coexisting in between those wires. Defects in the atom wires induce interband charge transfer, resulting in commensurate CDWs at low temperatures. Finally, manipulatable phase slips with fractional charge and spin are observed for the first time in a CDW in real space.

atom wires
electronic instabilities
structural fluctuations
charge density wave
scanning tunneling microscopy
silicon surfaces

http://resolver.tudelft.nl/uuid:e380b714-d980-4544-af57-4515bca3ead8

978-90-8593-012-9

Institutional Repository

doctoral thesis

(c) 2006 P.C. Snijders