Up-Conversion\nPhotoluminescence Reconfiguration in\nSilicon by Inner Microstructure Control of Hybrid Plasmonic-Semiconductor\nNanoparticles

Hybrid metal–semiconductor nanostructures unifying\nplasmonic\nand high-refractive-index materials in a single resonant system demonstrate\na wide set of unique optical properties. Such systems are a perspective\nfor a broad palette of applications, but the link between their inner\nstructure and optical properties is a very sensitive issue, which\nis still not revealed. Here, we describe the influence of internal\nmicrostructure of a hybrid gold–silicon nanoparticle (the gold\nnanoparticle with embedded silicon nanograins) on the up-conversion\nwhite-light photoluminescence. The evolution in the internal microstructure\nof the system during thermal treatment up to 500 °C is tracked <i>in situ</i> through the HAADF and EDS STEM techniques. The studies\nshow the redistribution of the materials inside the hybrid nanoparticle\nand the reduction of the silicon nanograin numbers under heating without\nan external modification of the nanoparticle shape. We have established\nnumerically that the dependence of the enhancement factor spectral\nwidth on the <i>S</i>/<i>V</i> ratio of the nanoparticle\nplasmonic component is close to the linear behavior. The shrinkage\nof the photoluminescence spectrum (up to 42%) of the hybrid nanoparticle\nreconfigured by laser exposure and thermal treatment is shown experimentally,\nwhich supports our numerical conclusions. The results shed light on\nthe connection of optical properties of complex hybrid systems with\ntheir complex internal composition, providing a powerful tool to control\ntheir optical properties through microstructure rearrangement. They\nalso open the way to the development of reconfigurable silicon-based\nup-conversion light nanosources for integrated optical devices and\nbiophotonics.