  Typical measurements of nanowire devices rely on end-to-end measurements to
reveal mesoscopic phenomena such as quantized conductance or Coulomb blockade.
However, creating nanoscale tunnel junctions allows one to directly measure
other properties such as the density of states or electronic energy
distribution functions. In this paper, we demonstrate how to realize uniform
tunnel junctions on InSb nanowires, where the low invasiveness preserves
ballistic transport in the nanowires. The utility of the tunnel junctions is
demonstrated via measurements using a superconducting tunneling probe, which
reveal non-equilibrium properties in the open quantum dot regime of an InSb
nanowire. The method for high-quality tunnel junction fabrication on InSb
nanowires is applicable to other III-V nanowires and allows for new tools to
characterize the local density of states.
