Experimental and Theoretical Studies of the Surface Oxidation Process of Rare-Earth Tritellurides





Citation of Original Publication

Kopaczek, J., Yumigeta, K., Ibrahim, A., Sayyad, M. Y., Sinha, S., Sailus, R., Hays, P., Moosavy, S. T. R., Susarla, S., Ataca, C., Kudrawiec, R., Tongay, S., Experimental and Theoretical Studies of the Surface Oxidation Process of Rare-Earth Tritellurides. Adv. Electron. Mater. 2023, 2201129. https://doi.org/10.1002/aelm.202201129


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Recent studies have established Van der Waals (vdW) layered and 2D rare-earth tritellurides (RTe ₃) as superconductors and near room-temperature charge density wave (CDW) materials. Their environmental stability raises nat-ural 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 RTe ₃ systems involving a variety of metals such as La, Nd, Sm, Gd, Dy, and Ho. The atomic force microscopy (AFM) and scan-ning 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 oxi-dization. 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 LaTe ₃ compared to the least stable HoTe ₃. Comprehensive quantum mechanical simulations reveal that environmental degradation originates from a strong oxidizing reaction with O ₂ 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 forma-tion, which directly impact the aging characteristics of RTe ₃ layers. Interest-ingly, optical and electrical measurements show that the CDW response is still observed in aged RTe ₃ 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