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arXiv 2111.13554cond-mat.mtrl-sci
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X射线对分布函数分析对非晶Ta2O5薄膜局域结构的深入研究

Deep insights into the local structure of amorphous Ta2O5 thin films by X-ray pair distribution function analysis

Alberto Martinelli, Mauro Giovannini, Martina Neri, Gianluca Gemme

摘要:

氧化钽(Ta 2 O 5)的非晶膜被广泛应用于构建用于干涉引力波探测器(诸如激光干涉仪引力波天文台(LIGO))的高反射镜。尽管有大量的研究,非晶态Ta 2 O 5的结构特性在局部尺度上仍然值得进一步研究。这些信息是必不可少的任何尝试,以了解这种重要的材料的属性,并没有属性建模的努力,可以预期产生可靠的信息,直到在非晶相的局部结构得到更好的理解。本文报道了用离子束溅射法制备的纯Ta_2 O_5和掺Ti非晶Ta_2 O_5薄膜的同步辐射X射线对分布函数的分析结果。结果表明:(1)非晶态Ta_2 O_5中Ta原子的排列与高压Z-Ta_2 O_5多晶型物中Ta原子的排列非常相似,而O原子的拓扑性质与δ-Ta_2 O_5中观察到的相似:(2)非晶态Ta_2 O_5中的结构相关性在~ 5埃以上开始消失,在r > 10埃时由于无序而被完全抑制; 3)Ti取代后的Ta 2 O 5非晶薄膜在热处理后仍保持着短程拓扑有序性,而纯Ta 2 O 5薄膜在热处理后局部结构发生了明显的重排。

英文摘要:

Amorphous films of tantalum oxide (Ta2O5) are widely applied to build highly reflective mirrors used in interferometric gravitational wave detectors, such as the Laser Interferometer Gravitational Wave Observatory (LIGO). Despite a large number of studies, the structural properties of amorphous Ta2O5 at the local scale still deserve several further investigations. Such information is essential to any attempt to understand the properties of this important material and no property modelling efforts can be expected to yield reliable information until the local structure in the amorphous phase is better understood. In this paper we report the results obtained by analysing the synchrotron X-ray pair distribution functions of pure and Ti-doped amorphous Ta2O5 film, deposited by ion beam sputtering, as prepared and after a thermal treatment. As a result, it is found that 1) the arrangement of Ta atoms in amorphous Ta2O5 strongly resembles that characterizing the high-pressure Z-Ta2O5 polymorph, whereas the topological properties of O atoms resembles that observed in delta-Ta2O5; 2) structural correlations in amorphous Ta2O5 start to vanish above ~ 5 Angstrom and are completely suppressed for r > 10 Angstrom on account of disorder; 3) Ti substitution retains the short-range topological ordering characterizing the as prepared Ta2O5 amorphous film even after thermal treatment; conversely, pure Ta2O5 films undergoes a significant rearrangement of the local structure after thermal treatment.

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