Hybrid Molecular Beam Epitaxy for Single-Crystalline Oxide Membranes with Binary Oxide Sacrificial Layers
Hybrid Molecular Beam Epitaxy for Single-Crystalline Oxide Membranes with Binary Oxide Sacrificial Layers
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DOI：
10.1021/acsnano.3c11192
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发表时间：
2024-02-05
期刊：
影响因子：
17.1
通讯作者：
Jalan，Bharat
中科院分区：
文献类型：
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作者：
Varshney，Shivasheesh;Choo，Sooho;Jalan，Bharat
用于合成氧化膜的薄膜剥离技术的进步使得用结构和化学不相容的材料制造人工组装异质结构成为可能。牺牲层法是一种很有前途的方法，可以从相容的材料系统中剥离生长膜，允许它们与不同的材料集成。然而，传统的牺牲层通常具有复杂的化学计量，从而限制了它们的实用性和适应性，特别是在考虑分子束外延（MBE）等技术时。这就是易于生长的具有岩盐晶体结构的二元碱土金属氧化物有用的地方。这些氧化物，包括（Mg, Ca, Sr, Ba）O，可以作为牺牲层，与传统的牺牲层相比，覆盖更广泛的晶格参数范围，并且容易溶解在去离子水中。在这项研究中，我们展示了单晶钙钛矿SrTiO3（STO）在由晶体SrO， BaO和Ba1-xCaxO薄膜组成的牺牲层上的外延生长，采用混合MBE方法。我们的研究结果表明，当浸入去离子水中时，牺牲层快速（≤5分钟）溶解，促进了毫米尺寸的STO膜的制造。利用高分辨率x射线衍射、原子力显微镜、扫描透射电子显微镜、阻抗谱和散射型近场光学显微镜（SNOM），我们证明了具有块状固有介电特性的单晶STO膜。使用碱土金属氧化物作为牺牲层可能会简化膜合成，特别是用MBE，从而扩大研究和应用的可能性。
The advancement in thin-film exfoliation for synthesizing oxide membranes has led to possibilities for creating artificially assembled heterostructures with structurally and chemically incompatible materials. The sacrificial layer method is a promising approach to exfoliate as-grown films from a compatible material system, allowing for their integration with dissimilar materials. Nonetheless, the conventional sacrificial layers often possess an intricate stoichiometry, thereby constraining their practicality and adaptability, particularly when considering techniques such as molecular beam epitaxy (MBE). This is where easy-to-grow binary alkaline-earth-metal oxides with a rock salt crystal structure are useful. These oxides, which include (Mg, Ca, Sr, Ba)O, can be used as a sacrificial layer covering a much broader range of lattice parameters compared to conventional sacrificial layers and are easily dissolvable in deionized water. In this study, we show the epitaxial growth of the single-crystalline perovskite SrTiO3(STO) on sacrificial layers consisting of crystalline SrO, BaO, and Ba1–xCaxO films, employing a hybrid MBE method. Our results highlight the rapid (≤5 min) dissolution of the sacrificial layer when immersed in deionized water, facilitating the fabrication of millimeter-sized STO membranes. Using high-resolution X-ray diffraction, atomic-force microscopy, scanning transmission electron microscopy, impedance spectroscopy, and scattering-type near-field optical microscopy (SNOM), we demonstrate single-crystalline STO membranes with bulk-like intrinsic dielectric properties. The employment of alkaline earth metal oxides as sacrificial layers is likely to simplify membrane synthesis, particularly with MBE, thus expanding the research and application possibilities.