Field Effects in Plasmonic Photocatalyst by Precise SiO₂ Thickness Control Using Atomic Layer Deposition

Abstract

We report on TiO2 thin films with superior photocatalytic efficiency due to an increase in its exciton carrier generation induced by the plasmonic field of the underlying silver nanoparticles. TiO2 thin films are deposited on supported silver nanoparticles and are separated from each other by a fine-tunable thickness of SiO2 interlayer. The TiO2(15 nm)/SiO2/Ag nanoparticle architectures with systematic variation of SiO2 interlayer thickness of 2, 5, 10, and 20 nm show systematic increase in photocatalytic efficiency with decrease in the SiO2 thickness. The efficiency enhancement is shown to be caused by plasmonically enhanced carrier generation, which was confirmed through photocurrent measurements and Raman spectroscopy. With a 2 nm SiO2 interlayer that exhibited the best photocatalytic performance, a 3 times increase in photocurrent density, and a 200 times increase in Raman signal intensity of TiO2 is found. Atomic layer deposition was employed to achieve precise film thickness control of SiO2 and TiO2 layers.