Revealing electrical and mechanical degradation of Ni/Bi2Te3 interface through the quantitative interfacial diffusion analysis

Abstract

Bismuth telluride (Bi₂Te₃)-based thermoelectric devices exhibit significant potential for energy harvesting and thermal management. However, device reliability and further development are critically limited by interface-induced failures, largely because quantitative failure analysis methods are lacking. This study systematically investigates interfacial degradation mechanisms and establishes a method for device lifetime prediction. First, accelerated thermal stress experiments are designed to analyze the Ni diffusion behavior at interface of different-type Bi₂Te₃-based TE materials, thereby determining the quantitative relationship among temperature (T), duration (t), activation energy (ΔE) and diffusion coefficient (D). Besides, the Ni diffusion depth ($x$) is confirmed to scale linearly with the square root of time ($x\propto t^{1/2}$) for a given diffusion coefficient, which is consistent with Fick's second law ($D=x^2/4t$). Moreover, both interfacial specific contact resistivity (${\rho }_c$) and tensile strength (${\sigma }_s$) exhibit linear correlations with Ni diffusion depth under a specific degradation mechanism, enabling quantitative assessment of interface stability. Ultimately, adopting standard resistance failure criteria, we completely propose a method for quantitative lifetime prediction, which might provide universal applicability for the reliability assessment of thermoelectric devices and advance the prediction method of interface-induced failure analysis.