Interwire coupling for In(4 x 1)/Si(111) probed by surface transport

The In/Si(111) system reveals an anisotropy in the electrical conductivity and is a prototype system for atomic wires on surfaces. We use this system to study and tune the interwire interaction by adsorption of oxygen. Through rotational square four-tip transport measurements, both the parallel $({\ensuremath{\sigma}}_{||})$ and perpendicular $({\ensuremath{\sigma}}_{\ensuremath{\perp}})$ components are measured separately. The analysis of the I(V) curves reveals that ${\ensuremath{\sigma}}_{\ensuremath{\perp}}$ is also affected by adsorption of oxygen, showing clearly an effective interwire coupling, in agreement with density-functional-theory-based calculations of the transmittance. In addition to these surface-state mediated transport channels, we confirm the existence of conducting parasitic space-charge layer channels and address the importance of substrate steps by performing the transport measurements of In phases grown on Si(111) mesa structures.