Transport Measurements on Individual Branched Nanostructures

We have made electrical measurements on individual branched (``Y-junction") carbon nanotubes. After isolation on silicon substrates and identification via electron microscopy, photo and e-beam lithography were used to deposit metal electrodes ($e.g.$ Au/Ti) onto individual branches of the nanostructures, including 4-probe configurations across a branch point (Y-junction). Various post-processing procedures, such as rapid thermal annealing and electron beam welding, were employed in attempts to improve contact resistances. Four-probe I-V measurements at room temperature yield varied intrinsic conductivity in these nanostructures (resistances between $10^4$ and $10^7\Omega$). Transmission microscopy reveals a fishbone internal structure, which could be responsible for the low conductance. We also report on the construction of ``divining rod'' cantilevers out of these branched nanotubes, using an etch-well technique, toward potential SPM applications, and on similar attempts using inorganic ($e.g.$ ZnO$_2$) nanowires.