Enhancing performance and thermal stability in GeTe thermoelectric joints with cobalt diffusion barrier

This study investigates the influence on thermoelectric properties of p-type GeTe after depositing cobalt (Co) diffusion barrier, and its ability on inhibiting the interfacial reactions that degrades thermoelectric performance of the joint at medium temperatures. Establishing stable interconnections within the joint is essential for ensuring the reliability of the device. By examining the improved thermoelectric properties of GeTe, the research highlights a discovering that the addition of a Co diffusion barrier significantly elevates figure of merit (zT) values of GeTe. Electron probe microanalysis (EPMA) reveals the diffusion of Co into GeTe and the formation of Co–Te intermetallic compounds. As the device ages, there is a substantial increase in contact resistivity at the GeTe joint. After depositing a Co layer and subjecting it to long-term aging, electrical conductivity improves, and thermal conductivity decreases. This improvement occurs because the Co atoms, which have diffused into the GeTe lattice, occupy Ge vacancy sites. Instead of degrading the zT value, Co deposition leads to a 56 % increase in the zT value for the p-type GeTe joint. This study emphasizes the improvement of the zT value rather than pursuing a high peak zT value for GeTe. These results affirm the role of Co as an effective diffusion barrier, contributing to the stability of the joint interface and the enhancement of the thermoelectric properties of GeTe material, offering a viable route for creating more efficient and durable thermoelectric energy conversion devices.