Infrared properties of Pt/cermet films
- 15 June 1991
- journal article
- research article
- Published by American Physical Society (APS) in Physical Review B
- Vol. 43 (17) , 13838-13845
- https://doi.org/10.1103/physrevb.43.13838
Abstract
The room-temperature transmittance and front reflectance of mid- and near-infrared radiation (400–15 000 ) by thin Pt/ cermet films prepared by electron-beam evaporation onto sapphire substrates were measured using a Fourier-transform spectrometer. The high value of the dc percolation threshold (0.50≤≤0.59) for the Pt/ system is evidence for correlations in the positions of the particles that can be described by coated-grain topologies. The data were compared with the predictions of five effective-medium models, which feature different microstructural topologies and values of . Published data on the dielectric functions of the component materials were used in the modeling. The Maxwell-Garnett and Bruggeman models do not describe the data adequately. A simplified version of a model by Sheng (≃0.455) provides an improved description. The best agreement is achieved for two models with adjustable, high values of . We conclude that an effective-medium theory is able to describe the infrared optical properties of a cermet system over a wide range of composition if proper account is taken of both the microstructure and the value of .
Keywords
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