Zintl layer formation during perovskite atomic layer deposition on Ge (001).
Zintl layer formation during perovskite atomic layer deposition on Ge (001).
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DOI：
10.1063/1.4972071
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发表时间：
2017-02
期刊：
影响因子：
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通讯作者：
Shen Hu;E. Lin;Ali K. Hamze;A. Posadas;Hsinwei Wu;David J. Smith;A. Demkov;J. Ekerdt
中科院分区：
文献类型：
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作者：
Shen Hu;E. Lin;Ali K. Hamze;A. Posadas;Hsinwei Wu;David J. Smith;A. Demkov;J. Ekerdt
利用原位x射线光电子能谱、反射高能电子衍射和密度泛函理论，分析了原子层沉积在Ge（001）上ABO3钙钛矿初始生长过程中的表面核能级偏移和表面结构，其中A = Ba, Sr, B = Ti, Hf, Zr。我们发现，在清洁的Ge表面上初始剂量的钡或锶（三异丙基环戊二烯基）前驱体产生的表面相具有与分子束外延沉积Ba时形成的0.5单层Ba Zintl层相同的化学和结构性质。当使用化学或元素金属源时，Ba、Sr和Ge的结合能也发生了类似的转移。在分子和原子金属源作用下，观察到的锗表面核能级位移与初始倾斜的锗表面二聚体的变平一致。用密度泛函理论计算发现，在碱土金属吸附过程中，二聚体的结合能转移和倾斜也发生了类似的变化。BaTiO3、SrZrO3、SrHfO3和SrHf0.55Ti0.45O3的高角度暗场扫描透射显微镜图像显示了锗二聚体之间Ba（或Sr）原子柱的位置。结果表明，前驱体吸附在Ge表面后，有机配体与前驱体解离，在分子束外延过程中产生与IV族半导体上钙钛矿生长至关重要的Zintl模板。
Using in situ X-ray photoelectron spectroscopy, reflection high-energy electron diffraction, and density functional theory, we analyzed the surface core level shifts and surface structure during the initial growth of ABO3 perovskites on Ge (001) by atomic layer deposition, where A = Ba, Sr and B = Ti, Hf, Zr. We find that the initial dosing of the barium- or strontium-bis(triisopropylcyclopentadienyl) precursors on a clean Ge surface produces a surface phase that has the same chemical and structural properties as the 0.5-monolayer Ba Zintl layer formed when depositing Ba by molecular beam epitaxy. Similar binding energy shifts are found for Ba, Sr, and Ge when using either chemical or elemental metal sources. The observed germanium surface core level shifts are consistent with the flattening of the initially tilted Ge surface dimers using both molecular and atomic metal sources. Similar binding energy shifts and changes in dimer tilting with alkaline earth metal adsorption are found with density functional theory calculations. High angle angular dark field scanning transmission microscopy images of BaTiO3, SrZrO3, SrHfO3, and SrHf0.55Ti0.45O3 reveal the location of the Ba (or Sr) atomic columns between the Ge dimers. The results imply that the organic ligands dissociate from the precursor after precursor adsorption on the Ge surface, producing the same Zintl template critical for perovskite growth on Group IV semiconductors during molecular beam epitaxy.