Work Function-Driven Hot Electron Extraction in a Bimetallic Plasmonic MIM Device

Abstract

The Localized Surface Plasmon Resonance (LSPR) can cause hot electrons to be emitted from metal nanostructures. A key issue is how these hot electrons can be efficiently extracted and used for example in energy harvesting or sensing applications. One way is to create a plasmonic metal–insulator–metal device (MIM). In a plasmonic MIM device hot electrons (or holes) are injected from a nanostructured surface electrode across the insulator into the back electrode, and a current flows. Here we present a new, bimetallic plasmonic MIM device where the different work functions of the metal electrodes result in a built-in electrical field which facilitates hot electron extraction. This eliminates the need for an externally applied bias. The nanostructured front electrode, with 52 nm wide and 10 μm long gold nanorods, is separated from the back electrode of aluminum by an insulator layer of Al2O3 with thicknesses varying between 3 and 18 nm. A maximum device responsivity of about 2.2 μA/W is measured when the Al2O...