Array of symmetric nanohole dimers with high sensitivity for detection of changes in an STT-RAM ultrathin dielectric layer

Abstract

A dimer nanohole array is proposed for in situ characterization of radiation damages in spin transfer torque random access memory (STT-RAM) multilayer structures. The structure supports a Fano resonance, which is about twice as sensitive to the refractive index changes in the surface layer, compared to the plasmonic mode in single nanohole arrays. A simplified STT-RAM multilayer of air/gold(5 nm)/MgO(10 nm)/gold(60 nm)/quartz substrate is considered as the platform for the dimer nanohole array. Our studies show that regarding the changes in the ultrathin MgO layer, the normalized figure of merit for this structure is up to more than 10 times larger than an array of single nanoholes. Furthermore, an improvement in bulk sensing performance over the array of nanohole heptamers is observed.