Hopping transport on a fractal: ac conductivity of porous silicon
- 15 January 1995
- journal article
- research article
- Published by American Physical Society (APS) in Physical Review B
- Vol. 51 (4), 2199-2213
- https://doi.org/10.1103/physrevb.51.2199
Abstract
We have measured the frequency dependence of the conductivity and the dielectric constant of various samples of porous Si in the regime 1 Hz to 100 kHz at different temperatures. The conductivity data exhibit a strong frequency dependence. When normalized to the dc conductivity, our data obey a universal scaling law, with a well-defined crossover in which the real part of the conductivity σ’ changes from an dependence to being proportional to ω. We explain this in terms of activated hopping in a fractal network. The low-frequency regime is governed by the fractal properties of porous Si, whereas the high-frequency dispersion comes from a broad distribution of activation energies. Calculations using the effective-medium approximation for activated hopping on a percolating lattice give fair agreement with the data.
Keywords
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