The effect of magnesium oxide buffer on the epitaxial growth of zinc oxide on sapphire

Y. F. Chen, H. J. Ko, S. K. Hong, T. Hanada, T. Yao, Y. Segawa

Research output: Contribution to journalConference articlepeer-review


ZnO single crystal thin film is on Al2O3(0001) substrate by plasma-assisted molecular beam epitaxy employing a thin MgO buffer layer. Using reflection high-energy electron diffraction (RHEED), we investigated the surface morphology evolution during the buffer and ZnO growth. We found that a few nanometers thick MgO layer deposited on Al2O3(0001) substrate strongly influences the subsequent growth of ZnO by promoting lateral epitaxial growth, which eventually leads to an atomically flat surface. As a result, (3×3) surface reconstruction of ZnO is observed and RHEED intensity oscillations are recorded. Structural investigations indicate that MgO with rock-salt crystallographic structure forms on the Al2O3(0001) surface as a template between the substrate and ZnO epilayer. Above that, the ZnO epilayer grows with little strain. The mosaicity in the ZnO film is suppressed by more than two orders as indicated by both symmetric and asymmetric X-ray rocking curves. The twin defect with a 30° in-plane crystal orientation difference is completely eliminated. Free exciton emissions at 3.3774 eV (XA) and 3.383 eV (XB) are observed in photoluminescence at 4.2 K further indicating the high quality of the resulting ZnO epilayers.

Original languageEnglish
Pages (from-to)123-128
Number of pages6
JournalMaterials Research Society Symposium Proceedings
Publication statusPublished - 2000
EventRecent Developments in Oxide and Metal Epitaxy -Theory and Experiment - San Francisco, CA, United States
Duration: 2000 Apr 232000 Apr 26


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