\textit{In situ} resistivity of endotaxial FeSi$_{2}$ nanowires on Si(110)

We present in situ UHV measurements of the resistivity of self-assembled endotaxial FeSi$_{2}$ nanowires (NWs) on Si(110) using a variable-spacing two-point method with an STM tip and a fixed contact pad. The resistivity at room temperature was found to vary with NW width with approximate values of $\rho_{\mathrm{NW}} =$ 220 $\mu \Omega $cm at 12 nm and 400 $\mu \Omega $cm at 3 nm. The increase at small W is attributed to boundary scattering, and is fit to the F-S model, yielding values of $\rho_{0} =$ 120 $\mu \Omega $cm and $\lambda $ $=$ 7 nm, for specularity parameter p $=$ 0.5. Upon partial oxidation by exposure to air, the resistivity of a 4 nm NW increased approximately 50{\%}. The resistivity is relatively insensitive to NW size or oxidation, which is attributed to a high concentration of point defects in the FeSi$_{2}$ structure, with a correspondingly short inelastic electron scattering length. It is remarkable that the defect concentration persists in very small structures.