Adatom-Induced Conductance Modification of In Nanowires: Potential-Well Scattering and Structural Effects

First-principles calculations on the influence of adatoms (In, Pb, H, O) on the Landauer conductance of Si substrate-supported atomic-scale In nanowires are performed. Despite the increase of the total (and partially even local) density of states at the Fermi level due to the adsorption, all adatom species lower the nanowire conductance. Apart from hydrogen, which barely changes the transport properties, the conductance drop is pronounced, ranging from 17% for Pb to 38% for In. It is related to potential-well scattering and/or structural deformations of the nanowires.

Figure 1

Potential energy surface calculated for H, O, In, and Pb adatoms on the $\mathrm{In}/\mathrm{Si}(111)\mathrm{\text{−}}(4\times 1)$ surface. Large and small balls indicate In and Si atoms, respectively. The minimum energy positions for the adsorbed species are marked.

Figure 2

Side views of (a) In and (b) Pb adatoms adsorbed on the $\mathrm{In}/\mathrm{Si}(111)\mathrm{\text{−}}(4\times 1)$ surface.

Figure 3

Quantum conductance spectrum for electron transport along the wire direction (upper part) and total density of states (lower part) calculated for ideal and adatom-modified $\mathrm{In}/\mathrm{Si}(111)$ structures.

Figure 4

Adsorption induced changes (in a.u.) of the local density of states at $E_F$ projected on the plane of the Si(111) surface. Negative and positive values indicate local DOS depletion and accumulation with respect to the ideal $\mathrm{In}/\mathrm{Si}(111)$ system, respectively.

Figure 5

Averaged (see text) effective potential along the wire direction calculated for ideal and adatom-modified $\mathrm{In}/\mathrm{Si}(111)$ structures.

Figure 6

Quantum conductance spectrum for electron transport along the wire direction calculated for ideal and adatom-modified $\mathrm{In}/\mathrm{Si}(111)$ structures that do, however, not contain the adatom.