Plasmonic resonance characteristics of silver nanorod dimer on MIS tunnel junction

In this paper, the extinction spectrum and electric field distribution of silver nanorod dimer on the metal-insulator-semiconductor (MIS) tunnel junction are calculated by finite element simulation method, and the mode of peak position in the spectrum is analyzed. In the simulation, the surface plasmons polaritons (SPPs) are excited by the inelastic electron tunneling in the MIS tunnel junction and this excitation method can overcome the disadvantage of integration difficulty caused by the demand of additional optical elements in the traditional optical excitation. The results show that when two identical silver nanorods in silver nanorod dimer are placed end-to-end parallel or T-shaped vertically, there are two resonance peaks in the extinction spectrum, which correspond to the vertical mode and the vertical mode of the nanorods, respectively. When the dimer is composed of two identical silver nanorods placed side-to-side in parallel, there is only one resonance peak in the extinction spectrum, which corresponds to the vertical mode of the nanorods. When the gap distance between the silver nanorod dimer structure and the MIS tunnel junction increases, the resonant peak position in the extinction spectrum will appear blue shift. By calculating the field distribution, it is found that an obvious "hot spot" distribution exists in the gap between the nanorods and the MIS tunnel junction, which indicates that the local electric field at the gap is enhanced. The above results have certain reference significance for the design of small biomolecule measurement sensors based on electrically excited SPPs.