Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Resonant Microwave Absorption in Thermally Deposited Au Nanoparticle Films Near Percolation Coverage

Published

Author(s)

Jan Obrzut, Jack F. Douglas, Oleg A. Kirillov, Fred Sharifi, James A. Liddle

Abstract

We observe a resonant transition in microwave absorption in thin thermally deposited Au nanoparticle films near the geometrical percolation transition pc where the films exhibit a ‘fractal’ heterogeneous geometry. The absorption of incident microwave radiation increases sharply near the microwave percolation threshold near the geometric pc, consistent with effective medium theory (EMT) predictions. Both EMT and experiment indicate that the hierarchical structure of these films makes their absorption insensitive to the microwave radiation wavelength  so that the singular absorption of microwave radiation pc is observed over a broad frequency range between 100 MHz and 20 GHz. Previous observations indicate that the interaction of electromagnetic radiation with randomly distributed conductive scattering particles gives rise to localized resonant modes and our measurements indicate that this adsorption process is significantly enhanced for microwave radiation in comparison to ordinary light. In particular, near the percolation transition a portion of the injected microwave power is stored within the film until dissipated. Finally, we find that the measured surface conductivity  s of our Au films can be quantitatively described at all Au concentrations by generalized effective medium (GEM) theory, where the fitted conductivity percolation exponents, and pc itself, are consistent with known two-dimensional estimates. Our results demonstrate that microwave measurements provide a powerful means of remotely measuring the electromagnetic properties of highly heterogeneous conducting films, enabling the purposeful engineering of the electromagnetic properties of thin films in the microwave frequency range through the fabrication of ‘disordered’ films of conducting particles such as metal nanoparticles, carbon nanotubes, etc.
Citation
Langmuir
Volume
29
Issue
28

Keywords

semi-continuous films, microwave conductance, absorptance, percolation

Citation

Obrzut, J. , Douglas, J. , Kirillov, O. , Sharifi, F. and Liddle, J. (2013), Resonant Microwave Absorption in Thermally Deposited Au Nanoparticle Films Near Percolation Coverage, Langmuir (Accessed May 25, 2024)

Issues

If you have any questions about this publication or are having problems accessing it, please contact reflib@nist.gov.

Created June 19, 2013, Updated February 19, 2017