Experimental and Theoretical Studies of the Surface Oxidation Process of Rare‐Earth Tritellurides
Experimental and Theoretical Studies of the Surface Oxidation Process of Rare‐Earth Tritellurides
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DOI：
10.1002/aelm.202201129
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发表时间：
2023-02
影响因子：
6.2
通讯作者：
J. Kopaczek;K. Yumigeta;A. Ibrahim;M. Sayyad;S. Sinha;R. Sailus;P. Hays;Seyed Tohid Rajaei Moosavy;S. Susarla;C. Ataca;R. Kudrawiec;S. Tongay
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文献类型：
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作者：
J. Kopaczek;K. Yumigeta;A. Ibrahim;M. Sayyad;S. Sinha;R. Sailus;P. Hays;Seyed Tohid Rajaei Moosavy;S. Susarla;C. Ataca;R. Kudrawiec;S. Tongay
最近的研究已经建立了货车德瓦尔斯（vdW）层状和二维稀土三碲化物（RTe 3）作为超导体和近室温电荷密度波（CDW）材料。由于在其他碲基层状晶体中观察到的老化/稳定性效应，它们的环境稳定性引起了自然关注。在这里，结果建立了这些RTe 3系统的稳定性和环境老化特性，涉及各种金属，如La，Nd，Sm，Gd，Dy和Ho。原子力显微镜（AFM）和扫描电子显微镜（SEM）的结果表明，所有的RTe 3片氧化形成薄的TeOx层，主要局限于表面，边缘和晶界。时间分辨原位拉曼光谱测量用于理解不同镧系金属阳离子的氧化过程的动力学，并建立它们对氧化的相对稳定性/弹性。总体结果表明，vdW层显示出更高的空气稳定性，因为4f电子数从Ho到La降低，导致最稳定的LaTe 3相比，最不稳定的HoTe 3。全面的量子力学模拟表明，环境退化源于与O2分子的强氧化反应，而湿度（H2O）起着微不足道的作用，除非Te空位存在。此外，模拟解释了4f电子对功函数和Te空位形成的影响，这直接影响RTe 3层的老化特性。有趣的是，光学和电学测量结果表明，CDW响应仍然观察到在老化的RTe 3层由于底层的原始/非氧化的RTe 3层的存在下，除了CDW转变温度增加，由于厚度效应。总体结果首次对这些材料进行了深入的环境老化研究，可用于设计和设计其化学稳定性、表面性能和整体CDW特性。
Recent studies have established Van der Waals (vdW) layered and 2D rare‐earth tritellurides (RTe3) as superconductors and near room‐temperature charge density wave (CDW) materials. Their environmental stability raises natural concern owing to aging/stability effects observed in other tellurium‐based layered crystals. Here, the results establish the stability and environmental aging characteristics of these RTe3 systems involving a variety of metals such as La, Nd, Sm, Gd, Dy, and Ho. The atomic force microscopy (AFM) and scanning electron microscopy (SEM) results show that all the RTe3 sheets oxidize to form thin TeOx layers that are primarily confined to the surface, edges, and grain boundaries. Time‐resolved in situ Raman spectroscopy measurements are used to understand the kinetics of the oxidization process for different lanthanide metal cations and establish their relative stability/resilience to oxidization. Overall results indicate that the vdW layers show higher air stability as the 4f electron number decreases going from Ho to La, resulting in the most stable LaTe3 compared to the least stable HoTe3. Comprehensive quantum mechanical simulations reveal that environmental degradation originates from a strong oxidizing reaction with O2 molecules, while humidity (H2O) plays a negligible role unless Te vacancies are present. Moreover, the simulations explain the effects of 4f electrons on the work function and Te vacancies formation, which directly impact the aging characteristics of RTe3 layers. Interestingly, optical and electrical measurements show that the CDW response is still observed in aged RTe3 layers owing to the presence of underlying pristine/nonoxidized RTe3 layers, except CDW transition temperatures increase due to the thickness effect. Overall results offer the first in‐depth environmental aging studies on these materials, which can be applied to engineer and design their chemical stability, surface properties, and overall CDW characteristics.