Excess (1f) noise in metals

We have measured the temperature dependence of the excess ($\frac{1}{f}$) voltage noise in thin films of the group-$\mathrm{I}B$ transition metals and in Ni. In the group-$\mathrm{I}B$ metals, the magnitude of the noise increases rapidly with temperature below room temperature and reaches a peak in Ag and Cu at $T_p\simeq 410$ K and $T_p\simeq 490$ K, respectively. In Ag, the noise dips through a valley at approximately 520 K, and increases again up to 600 K, while in Au there is flattening but no peak up to 525 K. In Ni, a somewhat slower increase in noise magnitude with temperature is observed, but in contrast to model predictions, which suggest a sharp peak in the noise at the Curie point, only peak structure is observed near $T_c$. Measurements of the power spectrum $S_v\mathrm{}\left(f\right)\mathrm{}$ ($\propto f^{-\alpha }$) show that $\alpha$ decreases slowly with increasing temperature for all four metals. The role of the substrate is examined by measuring the noise in films on substrates whose thermal properties differ greatly (sapphire and fused silica). A comparison of the results leads to the identification of two types of noise in metal films and the explanation of some apparent contradictions in existing data.