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Conference Paper
Suppressing Interfacial Reactions and Elemental Diffusion in Bi2Se3/Nb Superconducting Heterostructures by Process-Controlled Growth
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- Authors
- Dae-Hyung Cho, Tae-Ha Hwang, Yong-Duck Chung, Suji Lee, Woo-Jung Lee
- Issue Date
- 2026-05
- Citation
- European Materials Research Society (E-MRS) Meeting 2026 (Spring), pp.1-2
- Publisher
- European Materials Research Society (E-MRS)
- Language
- English
- Type
- Conference Paper
- Abstract
- Heterostructures composed of Bi2Se3 and Nb, including Bi2Se3/Nb and Nb/Bi2Se3/Nb geometries, are promising platforms for superconducting proximity effects and quantum device applications. For such systems, maintaining the intrinsic properties of each layer while forming a well-defined interface is essential. However, the Bi2Se3/Nb interface is highly susceptible to interfacial reactions and degradation of Bi2Se3 film quality. Although cleavage-based approaches have been reported to access clean interfaces, their applicability is limited by poor process reproducibility and device compatibility. In this work, the effects of Bi2Se3 deposition conditions on film quality and Bi2Se3/Nb interfacial characteristics are systematically investigated by varying the substrate, post-deposition annealing temperature, and the repetition number of Bi and Se deposition cycles. Bi2Se3 thin films with a thickness of approximately 20 quintuple layers were grown by alternating thermal evaporation of Bi and Se in a vacuum chamber below 10-7 Torr. Nb superconducting thin films were deposited by DC magnetron sputtering. For Bi2Se3 deposited on Nb, annealing above 175 °C significantly enhances the diffusion of oxygen and Nb into the Bi2Se3 layer, resulting in dominant Bi-O and Nb-Se bonding and a reduction in Bi2Se3 thickness. In contrast, annealing at temperatures below 150 °C suppresses oxygen and Nb diffusion, preserving Bi-Se bonding. An interfacial layer of approximately 5 nm, attributed to an NbxSey phase, is consistently observed over the investigated annealing temperature range. This behavior is distinctly different from Bi2Se3 deposited on SiO2, where Bi2Se3 remains stable without interfacial layer formation even above 200 °C, demonstrating the critical influence of Nb on Bi2Se3 film quality and interfacial chemistry. Furthermore, when Nb is deposited on Bi2Se3, an ultrathin interfacial layer of approximately 1 nm, also attributed to an NbxSey phase, is observed. The influence of the Bi/Se deposition repetition number is also examined. Increasing the repetition number effectively suppresses Nb diffusion into the Bi2Se3 layer, whereas a low repetition number leads to noticeable Nb diffusion and a deviation from stoichiometric Bi2Se3. The superconducting transition temperature of the underlying Nb layer remains above 8.7 K, indicating that Nb superconductivity is preserved during Bi2Se3 growth. These results provide practical guidelines for process-compatible engineering of Bi2Se3/Nb heterostructures for superconducting and quantum device applications.
- KSP Keywords
- Annealing temperature, Bi-Se, Deposition conditions, Influence of Nb, Interfacial characteristics, Interfacial chemistry, Interfacial layer, Layer formation, Nb diffusion, Postdeposition annealing(PDA), Practical Guidelines