Electronic and Transport Properties of Artificial Gold Chains

We study the electronic and transport properties of artificial Au atomic chains on a NiAl(110) surface template using state-of-the-art first principles calculations. Au chains display remarkable one-dimensional electronic properties that can be tuned by the selective adsorption of small molecules: a single CO group is shown to modulate the electronic wave functions, acting as a “chemical scissor” along the chain, to strongly modify the coherent transport properties of the system, and to help design one-dimensional nanodevices through artificial profiling of energy barriers.

Figure 1

(a) Top view of the gold chains on the $\mathrm{N}\mathrm{i}\mathrm{A}\mathrm{l}(110)\mathrm{\text{−}}(8\times 2)$ surface. (b) Side view of the CO molecule adsorbed on $\mathrm{A}\mathrm{u}/\mathrm{N}\mathrm{i}\mathrm{A}\mathrm{l}(110)\mathrm{\text{−}}(8\times 2)$. Au atoms are labeled with numbers from 1 to 8. Finite chains were simulated dropping atom $\mathrm{A}\mathrm{u}(8)$ (light sphere) from calculations. Calculated STM images of (c) infinite Au chain; (d) finite ${\mathrm{A}\mathrm{u}}_7$ chain; (e) CO @ infinite Au chain; (f) CO @ finite ${\mathrm{A}\mathrm{u}}_7$ chain on NiAl(110) surface. White arrows indicate the same symmetric STM pattern for different chains (see text). All images are calculated at $V=-0.4\mathrm{e}\mathrm{V}$ bias voltage.

Figure 2

Isosurface of selected Wannier functions centered on the ${\mathrm{A}\mathrm{u}}^{(3)}$ atom in clean (a), and CO@Au chains (b),(c). (a) Au-Au $\sigma$ bonding; (b) $\mathrm{A}\mathrm{u}\leftarrow \mathrm{C}$ $\sigma$ bonding; (c) unpaired ${\mathrm{A}\mathrm{u}}_{6s}$-derived state.

Figure 3

Transmittance of Au chain in the isolated configuration (shaded area), in the $\mathrm{A}\mathrm{u}/\mathrm{N}\mathrm{i}\mathrm{A}\mathrm{l}$ interface (dashed red line), and after CO adsorption (squared blue area). Vertical dotted line represents the Fermi level.

Figure 4

Average DFT (straight line) and steplike model (dotted line) of total potentials for (a) clean ${\mathrm{A}\mathrm{u}}_7$ and (b) CO@${\mathrm{A}\mathrm{u}}_7$ systems. Average square modulus of lowest energies DFT eigenfunctions (dash-dotted line) are shown; the energy separations are arbitrary. Vertical lines indicate the positions of Au atoms (1–7) along the chains.