Electrical testing of gold nanostructures by conducting atomic force microscopy

Abstract

We devised a method for the reliable electrical testing of nanoscale wire arrays using conducting probe atomic force microscopy (AFM) in ambient conditions. A key requirement of this approach is the formation of highly reproducible electrical contacts between the conducting tip and the sample. We discuss the basic mechanical and electrical criteria of nanocontacts and derive a force-controlled protocol for the formation of low-ohmic contacts. Tips sputter coated with platinum provided the mechanical stability for both tapping-mode imaging and the formation of low-ohmic contacts on gold samples. Nanostructures on the sample were identified by topographic imaging and subsequently probed using the AFM tip as a mobile electrode. We measured resistivities in arrays of nanowires or local potentials of wires within electrical circuits, and detected electrical failures, thermal gradients, and small geometrical variations. The ability of this instrument to address electrical characteristics with high spatial resolution makes it a powerful tool for lithography developments and on-chip monitoring of nanoscale circuits.