Self-organization of one-dimensional Au nanowires on a surface carbide and lateral electron quantization

The self-assembly of a periodic array of Au nanowires of $1\mathrm{nm}$ width on a prepatterned $\mathrm{W}\left(110\right)∕\mathrm{C}\text{−}R(15\times 3)$ substrate is demonstrated by low-energy electron diffraction and scanning tunneling microscopy. Angle-resolved photoemission reveals that Au $d$ states propagate along the wires and split up into distinct quantum-well states due to lateral confinement perpendicular to the wires. Our structural model emphasizes the role of the surface carbide as template for the self-organization.

Figure 1

LEED characterization at $65\mathrm{eV}$: Perfect $p(1\times 1)$ pattern of clean W(110) (a). The $R(15\times 3)$ carbide superstructure is rotated by 14° relative to the $\left[1\overline{1}1\right]$ direction of the W substrate (b). The $R(9\times 1)$ structure of 0.7 ML Au after annealing is assigned to nanowire formation.

Figure 2

STM study. Internal structure of the $\mathrm{W}\left(110\right)∕\mathrm{C}\text{−}R(15\times 3)$ structure with atomic resolution (a). The Au nanowires (b) appear in pairs (d). The first nanowire has a continuous and dense structure while every second nanowire consists of periodically arranged Au units (e). For comparision, submonolayer Au on clean W(110) forms no nanowires but a different large-scale reconstruction (c).

Figure 3

Structural model of self-organized Au nanostructures on $\mathrm{W}\left(110\right)∕\mathrm{C}\text{−}R(15\times 3)$. The carbide template (filled circles) consists of atomic C rows interconnected by zigzag C chains on the W(110) surface (open circles). The Au arrangement is shown as dashed lines where ellipses denote the cluster structure of every second nanowire.

Figure 4

Angle-resolved photoemission of the Au nanowire array. Au $d$ states show a dispersion for ${\mathbf{k}}_{\Vert }$ vectors along the nanowires (a) and size quantization perpendicular (b). $E\left({\mathbf{k}}_{\Vert }\right)$ dispersions extracted from the spectra are shown as well [(c) and (d)].