How transparent can a layer of gold be?

Gold films, made suitably thin, can exhibit high transparency and high conductivity at the same time. These properties are desirable, for example, when designing electrical contacts for light-emitting and light-harvesting devices. Gold deposited with conventional methods on transparent materials such as glass, however, has a strong tendency to form island films that exhibit strong optical (plasmonic) absorption and negligible electrical conductivity.

Now, using a simple surface preparation technique, researchers from the University of Iceland and Imperial College London have succeeded in suppressing this tendency to a degree where flat films down to approximately 5 nm thickness can be fabricated on glass using conventional deposition techniques. At this thickness, the theoretically expected transparency can exceed 80% in the visible range. Experiments show, however, that the actual transmission deviates from that of a perfect film, an effect that the group attributes to the presence of “fuzzy” interfaces between the gold and the neighbouring materials.

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