Abstract The epitaxial crystal quality of strontium aluminate (Sr3Al2O6) films under various Sr/Al ratios were systematically investigated by reactive molecular beam epitaxy. Efficient guiding rules for real-time optimization are summarized that a four-fold reconstructed reflection high-energy electron diffraction (RHEED) pattern and 4 periods of RHEED oscillations coinciding in the growth of one unit cell of Sr3Al2O6 is the key signature for the optimal growth condition. Following above rules, atomically smooth Sr3Al2O6 and freestanding SrTiO3 films with a full width at half maximum less than 0.03∘ (mainly limited by the substrates) were synthesized. The high-crystalline quality of freestanding SrTiO3 and atomically smooth interface between SrTiO3 film and Sr3Al2O6 were highlighted by the appearance of well-defined fringes from X-ray diffraction data and well-organized atomic distribution from electron microscopy. The epitaxial optimization of Sr3Al2O6 buffer layer with atomic flatness and high-crystalline quality will shed light on the synthesis of ultrathin freestanding oxide perovskite films, paving the way to the exploration of incorporating strongly correlated properties in conventional semiconductors for a generation of multifunctional electronic devices.

中文翻译：

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通过分子束外延对独立钙钛矿薄膜的原子光滑 Sr3Al2O6 进行外延优化

摘要 采用反应分子束外延法系统研究了不同Sr/Al比下铝酸锶(Sr3Al2O6)薄膜的外延晶体质量。总结了实时优化的有效指导规则，四重重构反射高能电子衍射 (RHEED) 模式和 4 个周期的 RHEED 振荡与 Sr3Al2O6 一个晶胞的生长重合是最佳生长的关键特征状况。按照上述规则，合成了原子级光滑的 Sr3Al2O6 和半高全宽小于 0.03∘（主要受基板限制）的独立 SrTiO3 薄膜。独立式 SrTiO3 的高结晶质量和 SrTiO3 薄膜与 Sr3Al2O6 之间的原子平滑界面通过 X 射线衍射数据中明确定义的条纹和电子显微镜中组织良好的原子分布突出显示。具有原子平坦度和高结晶质量的 Sr3Al2O6 缓冲层的外延优化将为超薄独立氧化物钙钛矿薄膜的合成提供线索，为探索在传统半导体中结合强相关特性以开发新一代多功能电子器件铺平道路。