Excess low frequency conduction noise in a granular composite

Granular composites consisting of 25% nickel as 8 nm diameter particles dispersed in an aluminium oxide matrix display excess conduction noise. Co-deposited films with resistance per square about 10⁵ ohms and negative temperature coefficient show a noise power spectral density $\text{S}{}_{\mathrm{v}}\text{(?) =}\text{S}{}_{\mathrm{v}}\text{(1)}\text{?}{}^{\mathrm{\alpha }}$ where α ? 1.10 ± 0.03 over the accessible spectral range of 0.1 Hz ? ? ? 5000 Hz. The amplitude 3 × 10^?15 ? S_v(1) ? 5 × 10^?12 V²Hz^?1, appears to increase approximately quadratically as the applied voltage V_s up to V_s ? 2.5 V and as the first power of V_s for 2.5 ? V_s < 35 V.