Abstract
In this study, the deposition, annealing process, and oxidation properties of HfNbTaTiZr high-entropy alloy thin films were thoroughly investigated. The films, approximately 250 nm thick, were deposited on MgO substrates by DC magnetron sputtering using a single target. The preparation temperature was identified as a key factor influencing the resulting structure. Amorphous films formed at room temperature, whereas nanocrystalline films, characterized by multiple intermetallic phases, were obtained either by deposition at elevated temperatures (600 °C – 750 °C) or through in situ annealing of amorphous films (600 °C – 700 °C). Positron annihilation spectroscopy revealed that nanocrystalline films predominantly contain vacancy-like misfit defects, with concentration decreasing as the preparation temperature increases. Additionally, amorphous films exhibited a high concentration of large vacancy clusters. X-ray photoelectron spectroscopy showed greater oxygen absorption in amorphous films due to their defective structure, with preferential oxidation of Zr and Hf. Further annealing of naturally oxidized films in a vacuum at temperatures up to 1400 °C led to films' recrystallization and eventually the formation of complex oxides, including ZrO2, HfO2, and various Mg-containing oxides, indicating a reaction with the MgO substrate. This work demonstrates the ability to fine-tune the microstructure and defect characteristics of high-entropy alloy films and highlights their direct correlation with oxidation properties.
Original language | English |
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Article number | 131642 |
Number of pages | 12 |
Journal | Surface and Coatings Technology |
Volume | 496 |
DOIs | |
Publication status | Published - 2025 |
Bibliographical note
Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-careOtherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.
Keywords
- Defects
- High-entropy alloys
- Positron annihilation spectroscopy
- Thin films
- X-ray photoelectron spectroscopy