Resistance Fluctuations Due to Hydrogen Diffusion in Niobium Thin Films

Fluctuations of the number of protons (H⁺) that scatter conduction electrons dominate lowfrequency resistance fluctuations in Nb films. The excess-noise spectra SV(f, T) obey a scaling law: fSV(f, T)〈δV²(T)〉=g(f/D(T)); for our geometry at $260<T<370$ K, SV(f, T)∝c₀(T)f^α, α=0 for fD(πL²) and α=3/2 for fD(πL²), c₀ is the H⁺ concentration, L is the film length, and the H⁺ diffusion coefficient is D(T)=D₀e^-E/kT with D(300 K)10^-6 cm²/s and E0.23 eV. Studies of 1/f noise evoke comparable mechanisms.