Effect of growth rate on the nucleation of α-Fe2O3 on α-Al2O3(0001) by oxygen-plasma-assisted molecular beam epitaxy

Abstract

We have investigated the role of growth rate on the nucleation of epitaxial α-Fe2O3 on α-Al2O3(0001). We show that a slow growth rate (∼1–2 Å/min) must be employed during growth of the first 30 Å in order to form relaxed, three-dimensional islands. A higher growth rate (∼0.1–0.3 Å/s) can then be used. Island coalescence occurs, resulting in a laminar surface for film thicknesses as low as a few hundred Å. If a higher initial growth rate is used, three-dimensional island growth is kinetically impeded, and film relaxation occurs by misfit dislocation generation. The film surface then roughens on a more macroscopic length scale, giving rise to a poor quality surface.