Terahertz conductivity of thin gold films at the metal-insulator percolation transition
Abstract
Terahertz time-domain spectroscopy is used to measure the complex conductivity of nanometer-thick gold films evaporated on silicon substrates in the far-infrared spectral region from $0.2\phantom{\rule{0.3em}{0ex}}\text{to}\phantom{\rule{0.3em}{0ex}}2.7\phantom{\rule{0.3em}{0ex}}\mathrm{THz}$. With increasing film thickness a characteristic crossover from an insulating to a conducting state via a percolation transition is observed. Of particular interest is the characteristic non-Drude behavior close to the transition. Whereas effective medium theory is inconsistent with our measurements in this regime, the Drude-Smith model, a generalization of the classical Drude model which incorporates carrier localization through backscattering, provides excellent fits to the observed complex conductivity. Applying this model we observe extreme values for the carrier scattering time at the percolation threshold.
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When film thickness is much smaller than the THz wavelength, the thin-film approximation can be applied, allowing the complex sheet conductivity to be extracted from transmission measurements.
“When film thickness is much smaller than the THz wavelength, the thin-film approximation can be applied, allowing the complex sheet conductivity to be extracted from transmission measurements [19,20].”
From Impact of Sub-picosecond Timing Errors on Complex Conductivity Extraction in Terahertz Time-Domain Spectroscopy of Ultrathin FAPbI3 Films (2026) · cites this paper as [20]
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“In THz-TDS studies, ultrathin-film behavior is generally characterized by the condition that the film thickness is much smaller than the THz wavelength ( λ ≫ d ), or more strictly: nd/λ ≪ 1 [19, 20].”
- Authors
- Walther, M., Cooke, D. G., Sherstan, C., Hajar, M., Freeman, M. R., & Hegmann, F. A.
- Affiliations
- University of Alberta (CA)
- Venue
- Physical Review B
- Publisher
- American Physical Society (APS)
- Published
- 2007-09-10
- Volume
- 76
- Issue
- 12
- ISSN
- 1098-0121 (ISSN-L)
- 1550-235X
- OpenAlex
- W1996774425
- Cited by
- 472
- References
- 61
- Citations by year
- 2026: 21 · 2025: 32 · 2024: 37 · 2023: 23 · 2022: 32 · 2021: 26 · 2020: 38 · 2019: 35 · 2018: 24 · 2017: 18 · 2016: 33 · 2015: 29 · 2014: 24 · 2013: 24 · 2012: 19
- FWCI
- 12.93
- Type
- journal article
- Language
- en
- Open access
- closed
- Locations
- Physical Review B (publishedVersion)
- Funders
- Natural Sciences and Engineering Research Council of Canada
- Topics
- Physical Sciences › Engineering › Electrical and Electronic Engineering › Terahertz technology and applications
- Physical Sciences › Physics and Astronomy › Atomic and Molecular Physics, and Optics › Surface and Thin Film Phenomena
- Physical Sciences › Engineering › Biomedical Engineering › Plasmonic and Surface Plasmon Research
- Keywords
- terahertz conductivity, gold thin films, complex conductivity, Drude-Smith model, carrier localization, backscattering, carrier scattering time, effective medium theory, film thickness dependence, far-infrared spectroscopy
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