Plasmon-Assisted Zone-Selective Repair of Nanoscale Electrical Breakdown Paths in Metal/Oxide/Metal Structures for Near-Field Optical Sensing

We report the selective repair of nanoscale oxide breakdown paths, by the localized surface plasmon effect, in the sandwiched oxide layer of a metal/oxide/metal structure. The test device has an aluminum/SiO2 stack, patterned in the form of a nanodisc (of diameter ∼100 nm) over a surface-oxidized, planar bottom aluminum electrode (i.e., Al/SiO2/AlOx/Al) and can support plasmonic resonance modes in the visible spectrum. Two-dimensional profiling of the top Al electrode by conductive atomic force microscopy, to obtain the distribution of the current within the nanodisc stack, reveals multiple breakdown paths in the SiO2/AlOx layers following an electrical stressing event. Reprofiling of the current after white-light illumination shows preferential repair of the breakdown paths within specific “zones” in the nanodisc and a corresponding decrease of the average leakage current. Breakdown paths situated near the top and bottom regions of the nanodisc are eliminated, leaving behind breakdown paths in the central part of the nanodisc. The resultant postillumination leakage current map of the nanodisc agrees very well with the two-dimensional optical-field enhancement pattern calculated using the finite-difference time-domain method, indicating that the zone-selective repair stems from enhanced optical fields arising from the localized surface plasmon effect in the top and bottom regions of the nanodisc. The findings of our study point to the prospect of realizing an electrically readable nanoscale metal/oxide/metal near-field optical sensor based on the light-triggered restoration of oxide breakdown.