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通过分子束外延法在经Mg预处理的蓝宝石衬底上制备了ZnO单晶薄膜,利用高分辨透射电镜、电子全息和X射线能谱对该薄膜的结构进行了细致的研究。结果表明,在蓝宝石衬底上预沉积一层很薄的Mg层,可以生长均匀Zn极性的ZnO外延薄膜。ZnO/MgO/蓝宝石的界面非常清晰锐利,同时在界面处可以观察到大约3个原子层的MgO。预沉积的Mg薄层对随后ZnO的极性选择起了关键性作用。
ZnO single crystal thin films were prepared by molecular beam epitaxy on Mg pre-treated sapphire substrates. The structure of the thin films was investigated by high-resolution transmission electron microscopy, electron holography and X-ray energy dispersive spectroscopy. The results show that a thin layer of Mg pre-deposited on a sapphire substrate can grow ZnO films with uniform Zn polarity. The interface of ZnO / MgO / sapphire is very sharp and sharp, while about 3 atomic layers of MgO can be observed at the interface. The pre-deposited Mg thin layer plays a key role in the subsequent polarity selection of ZnO.