Abstract MoTe2 is the least explored material in the Molybdenum-chalcogen family. Molecular beam epitaxy (MBE) provides a unique opportunity to tackle the small electronegativity difference between Mo and Te while growing layer by layer away from thermodynamic equilibrium. We find that for a few-layer MoTe2 grown at a moderate rate of ∼6 min per monolayer, a narrow window in temperature (above Te cell temperature) and Te:Mo ratio exists, where we can obtain pure phase 2H-MoTe2. This is confirmed using reflection high-energy electron diffraction (RHEED), Raman spectroscopy and X-ray photoemission spectroscopy (XPS). For growth on CaF2, Grazing incidence X-ray diffraction (GI-XRD) reveals a grain size of ∼90 A and presence of twinned grains. In this work, we hypothesis the presence of excess Te incorporation in MBE grown few layer 2H-MoTe2. For film on CaF2, it is based on >2 Te:Mo stoichiometry using XPS as well as ‘a’ and ‘c’ lattice spacing greater than bulk 2H-MoTe2. On GaAs, its based on observations of Te crystallite formation on film surface, 2 × 2 superstructure observed in RHEED and low energy electron diffraction, larger than bulk c-lattice spacing as well as the lack of electrical conductivity modulation by field effect. Finally, thermal stability and air sensitivity of MBE 2H-MoTe2 is investigated by temperature dependent XRD and XPS, respectively.

中文翻译：

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3D 衬底上少层 2H-MoTe 2 的 MBE 生长

摘要 MoTe2 是钼-硫属元素家族中探索最少的材料。分子束外延 (MBE) 提供了一个独特的机会来解决 Mo 和 Te 之间小的电负性差异，同时远离热力学平衡逐层生长。我们发现，对于以每单层约 6 分钟的中等速率生长的几层 MoTe2，存在温度（高于 Te 电池温度）和 Te:Mo 比率的窄窗口，我们可以获得纯相 2H-MoTe2。使用反射高能电子衍射 (RHEED)、拉曼光谱和 X 射线光电发射光谱 (XPS) 证实了这一点。对于在 CaF2 上的生长，掠入射 X 射线衍射 (GI-XRD) 显示晶粒尺寸约为 90 并且存在孪晶。在这项工作中，我们假设在 MBE 生长的几层 2H-MoTe2 中存在过量的 Te 掺入。对于 CaF2 上的薄膜，它基于 >2 Te:Mo 化学计量，使用 XPS 以及大于块体 2H-MoTe2 的“a”和“c”晶格间距。在 GaAs 上，它基于对薄膜表面 Te 微晶形成的观察，在 RHEED 和低能电子衍射中观察到的 2 × 2 超结构，大于体晶格间距以及缺乏场效应引起的电导率调制。最后，分别通过温度相关的 XRD 和 XPS 研究了 MBE 2H-MoTe2 的热稳定性和空气敏感性。大于体 c 晶格间距以及缺乏由场效应引起的电导率调制。最后，分别通过温度相关的 XRD 和 XPS 研究了 MBE 2H-MoTe2 的热稳定性和空气敏感性。大于体 c 晶格间距以及缺乏由场效应引起的电导率调制。最后，分别通过温度相关的 XRD 和 XPS 研究了 MBE 2H-MoTe2 的热稳定性和空气敏感性。