Imaging and Diffraction Study of Continuous α‐Fe<inf>2</inf>O<inf>3</inf> Films on (0001)Al<inf>2</inf>O<inf>3</inf>

Continuous α‐Fe2O3 films grown on bulk (0001)Al2O2 substrates by low‐pressure chemical vapor deposition have been studied by transmission electron microscopy and the observations compared to those obtained from discontinuous films at an earlier stage of the growth process. Plan‐view specimens revealed significant thermal stress in the continuous films, while cross‐sectional specimens showed that cracking occurs in thicker films. The free surface of the film and the film/substrate interface appeared sharp and flat, apart from growth ledges and steps. Weak‐beam imaging revealed a hexagonal misfit dislocation network consisting of perfect edge dislocations. Fine structure in the selected‐area diffraction patterns which corroborates these observations is also discussed. The misfit network of partial dislocations previously observed in the discontinuous films was not observed for the continuous films, indicating an effect of film thickness, growth rate, or surface preparation on the Fe2O3/(0001)Al2O3 interface structure. Copyright © 1992, Wiley Blackwell. All rights reserved