Suppressing electrostatic screening in nanostructured electrode arrays

An individual nanostructure provides very high electric field enhancement because the sharp curvature of the nanostructure tip amplifies the local electric field near the apex tip. However any practical nanostructured electrode is comprised of an ensemble (array) of nanostructures. In such systems, mutual electrostatic shielding (or screening) severely limits the maximum achievable electric field enhancement. In this paper, we discuss three approaches for suppression of shielding. These include--(1) reducing anode-to-cathode distance to less than the nanostructure-to-nanostructure spacing, (2) increasing length of selected individual nanostructures within the array, and (3) design of electrodes with multistage amplification. We show that these approaches are effective in alleviating electrostatic shielding and that the enhancement factor of the electrode array (ensemble) can be engineered to match that of the individual (isolated) nanostructure.