Jorge Luis Vazquez-Arce, Alessio Amoroso, Nicolas Perez, Jaroslav Charvot, Dominik Naglav-Hansen, Panpan Zhao, Jun Yang, Sebastian Lehmann, Angelika Wrzesińska-Lashkova, Fabian Pieck, Ralf Tonner-Zech, Filip Bureš, Annalisa Acquesta, Yana Vaynzof, Anjana Devi, Kornelius Nielsch, Amin Bahrami, Angewandte Chemie, e202422578, https://doi.org/10.1002/anie.202422578, 2025.
This study presents the first successful demonstration of growing elemental bismuth (Bi) thin films via thermal atomic layer deposition (ALD) using Bi(NMe2)3 as the precursor and Sb(SiMe3)3 as the co-reactant. The films were deposited at a relatively low temperature of 100 °C, with a growth per cycle (GPC) of 0.31–0.34 Å/cycle. Island formation marked the initial growth stages, with surface coverage reaching around 80 % after 1000 cycles and full coverage between 2000 and 2500 cycles. Morphological analysis revealed that the Bi grains expanded and became more defined as the number of ALD cycles increased. This coalescence is further supported by X-ray diffraction (XRD) patterns, which show a preferential shift in growth orientation from the (012) plane to the (003) plane as the film thickness increases. X-ray photoemission spectroscopy (XPS) confirmed the presence of metallic Bi with minimal surface oxidation. Temperature-dependent sheet resistance measurements highlight the semimetallic nature of Bi, with a room temperature resistivity of ≈200 μΩcm for the 2500 cycles Bi. Temperature-dependent sheet resistance was also associated with a transition in carrier-type dominance from holes at higher temperatures to electrones at lower temperatures.
Pingjun Ying, Ruben Bueno Villoro, Amin Bahrami, Lennart Wilkens, Heiko Reith, Dominique Alexander Mattlat, Vicente Pacheco, Christina Scheu, Siyuan Zhang, Kornelius Nielsch, Ran He, Advanced Functional Materials 34 (45), 2406473, https://doi.org/10.1002/adfm.202406473, 2024.
Thermoelectric technology has witnessed a resurgence in recent years due to increasing demands for sustainable energy sources and efficient cooling systems. Recently, the introduction of Te-free thermoelectric modules using non-toxic, abundant materials including p-type MgAgSb and n-type Mg3(Sb,Bi)2 marked a significant breakthrough. Despite promising performance, questions persist regarding long-term robustness and stability, especially in harsh environments. In this study, a thorough exploration of thermoelectric modules is conducted, focusing on their performance degradation under various conditions. Through elemental mapping analysis, degradation mechanisms are identified within the modules during cycling in argon environments, where atomic migrations and the formation of complex oxides at contact regions are key factors. Furthermore, cycling tests in air reveal significant degradation, prompting the exploration of protective strategies. Surface coatings using atomic layer deposition (ALD) emerge as a promising solution, particularly by HfO2, demonstrating superior protective effects. Furthermore, re-soldering effectively restores module performance is found, highlighting the importance of developing advanced soldering techniques to promote magnesium-based thermoelectric technology as a sustainable alternative to Bi2Te3. These findings emphasize the importance of exploring novel contact materials and demonstrate the potential of ALD as a universal approach to enhancing module reliability and robustness.
Shiyang He, Amin Bahrami, Xiang Zhang, Magdalena Ola Cichocka, Jun Yang, Jaroslav Charvot, Filip Bureš, Alla Heckel, Stephan Schulz, Kornelius Nielsch, Journal of the European Ceramic Society 43 (11), 4808-4813, https://doi.org/10.1016/j.jeurceramsoc.2023.04.026, 2023.
Van der Waals (vdWs) heterostructured materials have attracted considerable interest due to their intriguing physical properties. Here, we report on the deposition of BiSe by atomic layer deposition (ALD) using Bi(NMe2)3 and Se(SnMe3)2 as volatile and reactive Bi and Se precursors, respectively. The growth rate varies from 1.5 to 2.0 Å/cycle in the deposition temperature range of 90–120 °C. Higher deposition temperatures lead to increased grain sizes and enhanced crystallinity of resulting films. Further microstructure characterization reveals the formation of crystalline domains with varying orientations and nanotwinned boundaries. The presence of Bi-Bi zigzag bilayers and the formation of the BiSe phase were confirmed by the existence of the Bi-Bi binding energy peak in the XPS spectra and Raman spectra. Furthermore, the electrical conductivity of BiSe ranged from 1420 to 1520 S/cm due to the ultrahigh carrier concentration (2–3.5 × 1021 cm−3), which is the highest among undoped bismuth selenide-based materials.
S. He, A. Bahrami, X. Zhang, J. Julin, M. Laitinen, K. Nielsch, Materials Today Chemistry 32, 101650, https://doi.org/10.1016/j.mtchem.2023.101650, 2023.
Antimony (Sb) has distinct physical properties that make it a promising candidate for use in integrated phase-change photonics and tunable optical absorbers. In this work, we present atomic layer deposition (ALD) of Sb metal thin films using new precursor combinations produced from comproportionation reactions of antimony ethoxide (Sb(OEt)3) and Tris (dimethylamido)antimony (Sb(NMe2)3) with Tris (trimethylsilyl)antimony ((SiMe3)3Sb). The growth behaviors of the Sb thin films made from the Sb(OEt)3/(SiMe3)3Sb and Sb(NMe2)3/(SiMe3)3Sb precursor combinations showed different temperature dependencies at low deposition temperatures (60–80 °C). Furthermore, the deposition temperature had a significant impact on the oxidation of the deposited Sb film after exposure to air. XRD and Raman spectroscopy confirmed the high purity of the Sb films made with the Sb(OEt)3/(SiMe3)3Sb combination and deposited at 75 °C. The presence of a Sb2O3 phase deteriorated the electrical properties of deposited Sb films. However, the electrical conductivities of the purest Sb films prepared in this study were slightly higher than those previously reported for Sb-ALD films. This approach of Sb ALD can speed up actual applications of pure metals in electronic device fabrication and can potentially be extended to other main group metals.
