On the FIB Fabrication of Nano-Gap Metal Electrodes and Nature of their I-V Characteristics

Abstract

Copper and platinum electrodes with a nano-gap of ~100 nm have been fabricated by milling of thin metallic films by a focused ion beam (FIB) system. The current-voltage (I-V) characteristics of platinum electrodes are shown to follow V3/2 dependence in accordance with the classical Child-Langmuir’s law while those of copper electrodes measured inside the FIB chamber (residual pressure of ~10-6mbar) correspond to tunneling at low voltage and Fowler-Nordheim (F-N) quantum mechanical tunneling above 8.4V. The field enhancement factor (?) is found to depends on the surface homogeneity, cross-sectional area, gap of electrodes, and varies inversely with the applied voltage (value lies in the range of 8-21).