Fundamental Aspects of Ion Beam Assisted Deposition of Magnesium Oxide Template Films

The nucleation and growth of magnesium oxide (MgO) deposited using the ion beam-assisted deposition (IBAD) technique was investigated using a specially designed in-situ quartz crystal microbalance (QCM), which acted as the substrate during deposition. The mass accumulation of the growing film was collected while simultaneous reflected high-energy electron diffraction (RHEED) patterns were taken. IBAD MgO films deposited on the QCM with an amorphous silicon nitride layer showed an inflection point in the data. This inflection separated two distinct regions with the initial region having a slope greater than that of the final region. Experiments run at different ion-to-molecule ratios had similar inflection points that corresponded to a thickness of ~2 nm and could not be explained by an elementary growth and surface coverage model. Correlation of this inflection point with RHEED images showed that the point of inflection corresponds to the onset of in-plane texture. This result suggests that the IBAD MgO process is more complex than previously suggested and may depend upon a solid phase recrystallization process.