ZnO epitaxial films have been grown on sapphire substrates using molecular beam epitaxy (MBE). Elemental sources of Zn and O were used with a RF radical source being employed to increase the reactivity of the oxygen source gas. High-sensitivity pole figure measurements indicated that the films were uniquely (0 0 0 1) oriented with no trace of secondary orientations. The unique orientation is a consequence of the coincidental near zero lattice mismatch of the ZnO a lattice constant of 0.3250 nm and the sapphire c lattice constant over four or 0.3248 nm leading to the term uniaxial locked epitaxy. Atomic force microscopy of as-grown samples indicated that the films were flat with a RMS roughness of less than 0.4 nm. Two dimensional X-ray reciprocal space mapping of the ZnO(1 0 1̄ 4) asymmetric reflection using a triple axis configuration indicated that the lateral correlation lengths increased from several hundred nanometers for the case of (0 0 0 1)ZnO grown on sapphire(0 0 0 1) substrates to about 0.5 μm for growth on (1 1̄ 2 0)sapphire substrates. This is interpreted as being a consequence of less in-plane twisting of domains due to stress from lattice mismatch. Preliminary photo luminescence measurements indicate a dramatic increase in intensity with bound exciton features less than 0.7 meV.
|ジャーナル||Journal of Crystal Growth|
|出版ステータス||Published - 2000 2月|
|イベント||The 7th International Conference on Chemical Beam Epitaxy and Related Growth Techniques - Tsukuba, Jpn|
継続期間: 1999 7月 28 → 1999 7月 30
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