Electrical Transport and 1/f Noise in Au Nanoparticle Films

We studied the transport properties of Au nanoparticle films deposited on interdigitated electrodes with electrode spacings ranging from 0.1 $\mu $m to 1 $\mu $m. $I-V$ characteristics are found to be nonlinear and strongly dependent on both the coating and size of the nanoparticles. Current is thermally activated at low bias voltages, exhibits a threshold behavior, and scales as $I\propto (V-V_{th} )^\zeta $ at low temperatures. To complement dc transport measurements, we have performed noise measurements on some of the films. All the films that were studied exhibit 1/f type noise at low frequencies. The magnitude of the 1/f noise is smaller in devices with a larger device area, indicating that the 1/f noise is caused by intrinsic processes. The noise amplitude is found to be strongly temperature dependent between 40-300 K, with a local peak at around 100 K, and weakly dependent below 40 K. The noise data could not be fit by a single activated process, which would have led to an Arrhenius type temperature dependence. At low temperatures, the normalized noise spectra scaled as ${S_I } \mathord{\left/ {\vphantom {{S_I } {I^2}}} \right. \kern-\nulldelimiterspace} {I^2}\propto (V-V_{th} )^\gamma $. The relationship between the scaling exponents \textit{$\zeta $} and \textit{$\gamma $} is consistent with our prediction of $\gamma =1-\zeta $.