Visible Light Driven Hot-Electron Injection by Pd Nanoparticles: Fast Response in Metal-Semiconductor Photodetection

Hot-electron injection induced by plasmon decay enables ultrafast electron transfer in femtosecond scale and therefore endows metallic nanoparticles (MNPs) promising potentials in high-speed optoelectronics. With much higher density of states next to its Fermi level, palladium (Pd) can more efficiently launch hot electrons according to the theoretical prediction, as compared to the conventional plasmonic NPs. In this work, the optical properties of Pd NPs as well as the plasmon induced hot-electron injection are investigated through confocal Kelvin probe force microscopy. Analysis based on surface potential redistribution suggests Pd NPs can initiate dense hot-electron transfer in visible range. According to the photocurrent characterization of photo field effect transistors, in cooperation with TiOx the Pd NPs launch a rapid photocurrent increase with the excitation of 450 nm light as the hot-electron injection improves the electron depleting situation in TiOx thin film. The result confirms that Pd hot electrons can be energetic at visible range for photoelectric applications.