Optical and electrical properties of self-assembled, ordered gold nanocrystal/silica thin films prepared by sol-gel processing

Highly ordered gold nanocrystal (NC)/silica films are synthesized by self-assembly of water-soluble gold NC micelles and silica using a sol-gel spin coating technique. The optical properties are analyzed using ellipsometry and ultraviolet-visible spectroscopy. Transmission and absorption spectra were measured for wavelengths ranging from 200 to 2000 nm. The absorption spectra show a strong surface plasmon absorption band at ∼520 nm for all samples. Charge transport behavior of the films was examined using metal-oxide-semiconductor (MOS) and metal-insulator-metal (MIM) structures. MOS capacitor samples exhibit charge storage with discharge behavior dominated by electron transport within the gold NC arrays. Low temperature current-voltage measurements on MIM devices reveal electrical conduction with a thermal activation energy of ∼90 meV. For temperatures less than 100 K, the I-V characteristics of the NC film exhibits a strong coulomb blockade effect, with a threshold voltage of ∼0.5 V measured at 78 K.