The Role of Nucleation Surfaces in the Texture Development of Magnesium Oxide During Ion Beam Assisted Deposition

Both the structure and the type of the nucleation surface play a key role in texture development of IBAD MgO films. We have examined these features in Al₂O₃ and Y₂O₃ thin films using two different types of deposition methods, atomic layer deposition (ALD) and electron beam evaporation (EBE). Examination of EBE Al₂O₃ with in situ reflected high-energy electron diffraction (RHEED) films reveals the presence of a nanocrystalline structure that remains unchanged after and is insensitive to ion irradiation with 750 eV argon ions. In contrast, ALD Al₂O₃ examined with the same method reveals a featureless image that appears amorphous. Use of the ALD Al₂O₃ film can result in well-textured films with reasonable in-plane mosaic spread values (~ 14°) without process optimization. Similar results were obtained on ALD and EBE Y₂O₃ films, although, the EBE Y₂O₃ appeared amorphous in the RHEED even before exposure to the ion beam. The ALD Y₂O₃ film resulted in an in-plane texture of ~ 10°. Finally, bare silicon substrates were examined. It was found that even with the native oxide remaining on its surface, the silicon underneath was amorphized by the ion beam and provided a suitable surface for the deposition of biaxial textured MgO with an in-plane texture of ~ 7° FWHM.