Transport processes during the growth of oxide films at elevated temperature

Abstract

The current understanding of the growth of thermal oxide films in terms of the transport properties of the oxides is reviewed. Emphasis is placed on examining quantitative relationships between the film growth rate and other measurable parameters of the oxides. The theories of film growth which are expected to apply in the extreme limits of thick films (Wagner) and thin films (Cabrera and Mott) are outlined. Particular attention is given to examining the expected limits of validity of these theories and to the various ways in which their predictions can be tested experimentally. The growth of a selection of important oxides is then discussed in the light of these two theories. The examples (CoO, NiO, ${\mathrm{Fe}}_{3}$${\mathrm{O}}_{4}$, ${\mathrm{Cr}}_{2}$${\mathrm{O}}_{3}$, ${\mathrm{Al}}_{2}$${\mathrm{O}}_{3}$, and Si${\mathrm{O}}_{2}$) have been selected such that together they serve to test the theories, have technological relevance, and exhibit a wide variation in behavior. The dominant role of diffusion along oxide grain boundaries in controlling the growth of the crystalline oxides is highlighted.