Speaker
Description
The need for sustainable energy is nowadays well understood and multiple pathways are being explored, minimizing harmful by-products and energy waste in energy conversion processes. Thermoelectric effects have the potential to address these challenges, mainly by converting waste heat into reusable energy for industrial and domestic appliances [1].
Transition-metal nitrides (TMNs) are promising candidates for this purpose due to their favorable electronic and thermal properties. Among them, scandium nitride (ScN) is receiving considerable attention. The performance of bulk ScN is not sufficient for practical applications, but in recent years several techniques have been proposed to enhance its thermoelectric performance, primarily through the fabrication and use of nanostructured thin films [2,3].
The optimization of the thermoelectric performance of a material is a very complex task, as it requires acting separately on material properties that are strongly interconnected, such as electrical and thermal transport, maximizing the former while minimizing the latter. Achieving this goal requires a deep understanding of the mechanisms underlying these phenomena at the microscopic level.
Here we illustrate our work, in which we investigate the microscopic mechanisms underlying the variability observed in the thermoelectric response of ScN [4,5]. It is reasonable to hypothesize that this variability depends on the structural characteristics of the material, such as defects and the presence of heteroatoms in the crystal lattice. The Landauer approach allows us to relate the microscopic structures that compose the material to its macroscopic behavior, analyzing their contribution to the global properties [6].
Using this approach, we systematically analyze how different types of lattice imperfections—specifically oxygen impurities and nitrogen-site vacancies—affect electronic transport in ScN nanostructures. Defects are classified according to their symmetry (isolated, multiple contiguous, or associated with glide-type defects) and chemical nature. Our results identify two dominant defect classes with opposing effects on thermoelectric performance: (i) contiguous nitrogen vacancies, which enhance electrical conductivity but reduce the absolute value of the Seebeck coefficient, and (ii) oxygen substitutions coupled with nearby glide-type defects, which increase the absolute value of the Seebeck coefficient while hindering electrical conductivity [7].
[1]. J. He et al., Appl. Therm. Eng. 236, 121813 (2024).
[2]. P. Eklund et al., J. Mater. Chem. C 4, 3905 (2016).
[3]. B. Biswas et al., Phys. Rev. Mater. 3, 020301 (2019).
[4]. P.V. Burmistrova et al., J. Appl. Phys. 113, 153704 (2013).
[5]. J. More-Chevalier et al., Appl. Surf. Sci. Adv. 25, 100674 (2025).
[6]. S. Datta, Electronic transport in mesoscopic systems (Cambridge university press, 1997).
[7]. L. Cigarini et al., preprint (2025): https://tinyurl.com/2c4zw7rt
