Thickness Measurement of Epitaxially Grown Films

Abstract

MANY substances are known to grow epitaxially when deposited on suitable single crystal substrates. A review of epitaxial growth has been given by Pashley¹. The single-crystal film is of importance since its behaviour is easier to interpret than that of a polycrystalline film, in which both crystallite size and orientation are variable. Rock-salt crystal is frequently used as a substrate because the film can be easily removed from its surface by dissolving the underlying crystal. It is essential that the film be removed for study, in order that the strain associated with the epitaxial process be removed by annealing. Measurement of the thickness of such films raises a slight difficulty because a cleaved rock-salt surface, although flat over very small areas, is rarely flat enough to enable the usual multiple-beam fringe methods² to be applied directly.