MoO₃ films were grown on stepped c-plane sapphire substrates by molecular beam epitaxy using MoO₃ vapor from a conventional Knudsen cell. Stepped sapphire (0001) substrates were prepared by ex situ annealing at 1100–1300 °C in dry air. Step bunching typically resulted in multistepped surfaces with wide atomically smooth terraces. Ex situ annealing at 1100 °C followed by in vacuo annealing at 700 °C provided clean substrates for growth. Ultrathin films were grown at 450 °C via a self-limiting process that represents a balance between the incident MoO₃ flux and the desorption flux. Elongated bilayer islands (0.7-nm thick) were formed on sapphire (0001) terraces. Monocrystalline α-MoO₃ (010) thin films [(010)_α-MoO3∥(0001)_sapphire] were grown at 450 °C using a higher incident MoO₃ flux and characterized by atomic force microscopy, x-ray photoelectron spectroscopy, x-ray diffraction, and cross-sectional transmission electron microscopy. The step-terrace surface morphology of the monocrystalline films strongly suggests multilayer growth.

中文翻译：

---

通过分子束外延在阶梯式蓝宝石 (0001) 上生长的 MoO3 薄膜

MoO ₃膜使用来自常规克努森电池的MoO ₃蒸气通过分子束外延在阶梯式c面蓝宝石衬底上生长。阶梯蓝宝石（0001）衬底上通过制备易地退火在干燥空气一一零零年至1300年℃。阶梯聚束通常会导致多阶梯表面具有宽的原子级平滑阶地。在 1100 °C 下进行非原位退火，然后在 700 °C下进行真空退火，为生长提供了干净的衬底。超薄膜是在 450 °C 下通过自限过程生长的，该过程代表了入射 MoO ₃之间的平衡通量和解吸通量。在蓝宝石 (0001) 阶地上形成了细长的双层岛（0.7 纳米厚）。单晶 α-MoO ₃ (010) 薄膜 [(010) _α-MoO3 ∥(0001)_蓝宝石] 在 450 °C 下使用更高的入射 MoO ₃通量生长，并通过原子力显微镜、X 射线光电子能谱、x射线衍射和横截面透射电子显微镜。单晶薄膜的阶梯形表面形态强烈表明多层生长。