Abstract

Thin cross sections of titania-silica and zirconia-silica quarterwave stacks were prepared by ultramicrotomy and examined by transmission electron microscopy. Ultramicrotomy is a standard biological sample preparation technique originally developed for thin sectioning of soft tissue. In the present study, the thin films were deposited by reactive electron beam evaporation onto glass substrates at elevated temperatures. Electron-transparent cross-sectional slices were cut from these stacks and subsequently examined by transmission electron microscopy. The glassy structure of silica, the inhomogeneous crystalline morphology of zirconia, the noncrystalline anisotropy of titania, and the relationship between columnar growth and surface roughness with lateral dimensions of 3–10 nm were clearly observed. The improved resolution offered by ultramicrotomy also revealed the presence of a 2-nm thick nucleation layer in titania and a surface-smoothing effect by the silica. Thin-film microstructure analysis by ultramicrotomy offers several advantages over conventional shadow replication techniques. It provides direct imaging of the thin films in cross section, accurate thickness information, resolution not limited by a shadowing material, and image contrast which is largely independent of the specimen’s fracture mechanics. Equally important, microtomed thin sections allow direct chemical and crystalline structure analysis.

© 1985 Optical Society of America