THE EARLY STAGES OF MGO EPITAXY ON LATTICE-MATCHED CR0.7MO0.3(001)

We have investigated the structure and morphology of thin epitaxial overlayers of MgO on lattice-matched interlayers of Cr0.7Mo0.3 grown on MgO(001) substrates. Lattice matching results in unstrained MgO epitaxial films with short- and long-range structural order of comparable quality to those of buffer layers of MgO grown on MgO(001) under optimized step-flow growth conditions. In addition, the structural coherence of the oxide/metal interface is excellent due to lattice matching, in contrast to lattice-mismatched systems. However, MgO does not grow in a perfectly laminar fashion on Cr0.7Mo0.3 due to surface and interface free-energy imbalances; thin MgO films exhibit mean roughnesses of similar to 4 Angstrom with terrace widths of several hundred Angstrom. Nevertheless, the use of lattice-matched conducting interlayers between a bulk oxide substrate and an epitaxial thin film of the same material allows high-quality insulting oxides to be prepared on conducting substrates. This approach in turn permits the full arsenal of charged-particle spectroscopic, diffraction and imaging probes to be applied to investigations of the surface science of insulators.