Low-frequency noise in monodisperse platinum nanostructures near the percolation threshold

The percolation threshold p0 ≈ 0.6 is determined for monodisperse platinum nanostructures with 1.8-nm metallic particles deposited in a monolayer onto an insulating substrate through laser electrodispersion. It is shown that, in the “metallic” state (for p > p0), both the magnitude of the noise and its temperature dependence are close to those of pure metallic Pt layers. The frequency dependence of the normalized noise power spectral density is described by the relationship SI/I2 ∼ 1/fγ with the exponent γ close to unity. For current densities j ≥ 107−108 A/cm2, the noise power spectral density SI increases more rapidly with a further increase in the current as compared to I2 because of the current generating excess defects. For p < p0, the dependence of the conductivity σ on the temperature is adequately described by the standard relationship σ ∼ exp[−(T0/T)1/2]. The normalized noise power spectral density SI/I2 exceeds the corresponding value for a quasi-metallic structure by many orders of magnitude. The noise power spectral density SI is approximately proportional to the square of the current only for very low currents and increases steeply with a further increase in the current.