Concepedia

Noble-metal-based transparent infrared reflectors: Experiments and theoretical analyses for very thin gold films

Geoffrey B. Smith, Gunnar A. Niklasson, J. S. E. M. Svensson, Claes‐Göran Granqvist

Journal of Applied Physics · 1986 · 133 citations · 59 references

TL;DR

Very thin gold films on glass were fabricated by ion plating and conventional evaporation, characterized by spectrophotometry, and their optical behavior was modeled using effective medium theories and Drude theory with an anomalous relaxation energy dependence. Network gold films thinner than ~9 nm (IP) or ~15 nm (CE) exhibit near‑infrared transmittance plateaus that enhance solar transmission, and calculations show significant induced transmission in dielectric/gold/dielectric coatings, supporting the development of improved transparent infrared reflectors for energy‑efficient windows.

Abstract

Very thin gold films were prepared on glass by ion plating (IP) and by conventional evaporation (CE). Below a certain thickness—∼9 nm for IP and ∼15 nm for CE—the films comprised a metal network; above this thickness we found uniform films. Optical properties were recorded by spectrophotometry. Conspicuous near-infrared transmittance plateaus were seen in network films. This effect is conducive to high solar transmission. The spectral features were explained from effective medium theories based on the film structure. The uniform films were consistent with the Drude theory, provided that an anomalously large frequency dependence of the relaxation energy was invoked. Significant induced transmission was found in calculations on dielectric/gold/dielectric coatings. Our results lead to improved noble-metal-based transparent infrared reflectors for potential use on energy efficient windows.