Enhanced Interface Stability of Multilayer Bi2Te3/Ti/Cu Films after Heat Treatment via the Insertion of a Ti Layer.

The interface stability is of great significance for maintaining the high output performance of thin‐film thermoelectric devices. Here, it is demonstrated that by introducing a Ti layer and controlling its thickness, the interface stability relating to element diffusion, contact resistance, and mechanical strength can be regulated at Bi2Te3/Cu interfaces. After heat treatment, the multilayer interface with a thickness of 270 nm for the Ti layer has a stable structure that can suppress element diffusion, maintain a low specific contact resistivity (7.49 × 10−6 Ω cm2) and obtain an excellent critical load (58.1 mN). These characteristics are achieved because the Ti film with a thickness of 270 nm can keep multilayer interface stable, maintain the interface as effective junctions, and alleviate stress release. Due to the diffusion of Cu, the Cu‐Te compounds are formatted and Cu diffusion into Bi2Te3 is generated in the interfaces. Meanwhile, the results show that the Cu diffusion into Bi2Te3 has a greater impact on contact resistance than p‐CuTe in the interface. The work provides a general method for maintaining the reliability and stability of multilayer interfaces in thin‐film thermoelectric devices. [ABSTRACT FROM AUTHOR]