Plasmonic Hot Spots on Topological Insulator Nanotips for Enhancing Light Interaction with MoS2 Atomic Monolayer [invited]

Topological insulators (TIs) have unique topologically protected conducting surface and insulating bulk states, which provide a novel platform for plasmonic excitation and related nanoscale functional devices. Exploring plasmon-enhanced interactions between light and atomic-layered semiconductors in TI nanostructures is particularly significant for optoelectronic applications of TIs. Herein, the Sb₂Te₃ TI nanotips are fabricated by using focused ion beam lithography technique and the plasmonic hot spot behaviors are investigated on the TI nanotips. The numerical simulation shows that there exists a distinct reinforcement of light field on the Sb₂Te₃ TI nanotips, which stems from the TI-based plasmonic hot spot effect. Moreover, the obvious enhancement of photoluminescence (PL) emission from a molybdenum disulfide (MoS₂) monolayer integrated onto the Sb₂Te₃ TI nanotips is experimentally observed. The PL intensity of MoS₂ layer on the Sb₂Te₃ nanotips can be effectively improved by about five-fold due to the plasmonic hot spot-induced field reinforcement when compared with that of MoS₂ without the Sb₂Te₃ nanotips. These results will open a new avenue for optoelectronic applications of TIs, especially in nanoscale enhanced PL emission.