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Title: Why is 1/f resistance noise nearly universal in solids?
Plain: Resistance fluctuations in metals and semiconductors follow a 1/f spectrum over many decades of frequency. A broad spread of slow defect relaxation times can produce this, but why that spread is so generic is open.
Precise: The empirical Hooge relation $S_R(f)/R^2 = \alpha_H/(N_c f)$, with $N_c$ the number of carriers, holds over many decades of $f$ in metals and semiconductors. The McWhorter and Dutta-Horn picture attributes the noise to thermally activated fluctuators with a broad distribution of activation energies. Determine whether this picture accounts for all classes of $1/f$ resistance noise (mobility versus number fluctuations, metals versus semiconductors), and if not, which classes need a different mechanism.
Settled by: Systematic tests of the Dutta-Horn relation and of $\alpha_{H}$ against controlled defect density in several material classes, with the fluctuators identified microscopically.
Kind: phenomenon
Answer type: mechanism
References: (empty)
Literature status: open
Status note: (empty)
Posed since: 1925