Attempts at understanding the internal and external physical structure (i.e., morphology) of vapor-deposited thin films began with the discovery and early development of the PVD methods of sputtering by Grove in 1852  and thermal evaporation by Faraday in 1857 . This chapter presents a review of subsequent developments for optics.
The optical properties of thin-film coatings were the first properties to be studied. Faraday surmised in his 1857 Bakerian Lecture that the similarity between the optical properties of gold colloids, metallic gold leaf, and thermally evaporated coatings of gold (described as deflagrations of gold wire by the Leyden discharge [and] by the voltaic battery) indicated that the vapor-deposited coatings consisted of âparticles â¦ so small and so near, that two or more can act at once upon the individual atoms of the vibrating etherâ [175, p. 178]. By 1886 Kundt  had proposed a relation between the anisotropic optical properties of various thin films of metal deposited at oblique angles (with respect to the substrate plane) and, indirectly, their anisotropic morphology at the molecular level. Until World War II only moderate progress was made in understanding the relationships among preparation conditions, morphology, and optical propertiesâdue in part to the slow development of optical theories that take nanostructural morphology into account, and in part to the lack of characterization tools to directly view thin-film morphology at various length-scales down to the nanometer level.
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