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Journal of Physical Studies 15(4), Article 4703 [8 pages] (2011)
DOI: https://doi.org/10.30970/jps.15.4703 MORPHOLOGY AND ABSORPTION SPECTRA OF ULTRA-THIN FILMS OF SILVERI. M. Bolesta, A. V. Borodchuk, A. A. Kushnir, I. I. Kolych, I. I. Syworotka*
Faculty of Electronics Ivan Franko National University of Lviv, |
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We have studied the optical absorption spectra and morphology of ultra-thin films of silver which were deposited in a vacuum of $10^{-6}$ Torr on glass substrates. It was shown that in the field of mass thickness of $ d_m=1.1\ldots5.6$ nm structures there are the main elements of the particle as an ellipsoid with the dimensions of $\sim39-49$ nm. The fractal dimension of structures formed by metallic phase depends linearly on $d_m$.
In the absorption spectra of thin films there was observed the band in the region of 400\ldots500 nm which is associated with the surface plasmon resonance. With the growth of mass thickness the band shifts into the longwave region while the increasing of the absorption of a long-wave decline can be explained by a strong growth due to the uneven expansion of the number and size of clusters, their deviation from spherical shape and electrodynamic interaction between clusters in the light wave.
We proposed a criterion for determining the percolation threshold in films with the consideration of their absorption spectra. The received value percolation threshold introduced method is very well correlated with the values that are calculated for silver by other methods.
The fitting of optical spectrum bandwidth leading film $ d_m=17.5$ nm near the threshold of percolation with a model air-film-substrate succeed in evaluating the phenomenological parameter structure for this material.
PACS number(s): 78.66.Bz, 36.40.Gk, 78.20.-e