Forming reproducible non-lithographic nanocontacts to assess the effect of contact compressive strain in nanomaterials

Abstract

The application of electrical nanoprobes to measure and characterise nanomaterials has become widely spread.However, the formation of quality electrical contacts using metallic probes on nanostructures has not been directly assessed.We investigate here the contact electrical behaviour of non-lithographically formed contacts to ZnO nanowires and develop a method to reproducibly form contacts.The contacting method NWs relies on an electrical feedback to determine the point of contact, ensuring minimal compressive strain at the contact.This developed method is compared with the standard tip deflection contacting technique and shows a significant improvement to reproducibility.The effect of excessive compressive strain at the contact was investigated, with a change from rectifying to ohmic I-V behaviour observed as compressive strain at the contact is increased, leading to irreversible changes to the electrical properties of the NW.The potential effect of current annealing the nanowire and contacts was considered and shown not to be a major contributing factor to the change in I-V behaviour.This work provides an ideal method for forming reproducible non-lithographic nanocontacts to a multitude of nanomaterials.