Large-area nanofabrication of partially embedded nanostructures for enhanced plasmonic hot-carrier extraction

When plasmonic nanoparticles are coupled with semiconductors, highly energetic hot carriers can be extracted from the metal-semiconductor interface for various applications in light energy conversion. However, the current quantum yields for hot-electron extraction are generally low. An approach for increasing the extraction efficiency consists of maximizing the contact area between the surface of the metal nanostructure and the electron-accepting material. In this work, we developed an innovative, simple, and scalable fabrication technique that partially embeds colloidal plasmonic nanostructures within a semiconductor TiO₂ layer without utilizing any complex top-down nanofabrication method. The successful embedding is confirmed by scanning electron microscopy and atomic force microscopy imaging. Using visible-pump, near-IR probe transient absorption spectroscopy, we also provide evidence that the increase in the surface contact area between the nanostructures and the electron-accepting material leads to an increase in the amount of hot-electron injection into the TiO₂ layer.