The effects of diffusion barrier layers on the microstructural and electrical properties in CoSb3 thermoelectric modules

•2.5-μm-Thick layers of Au, Pt, and Ti as diffusion barrier layers were deposited on a CoSb3 leg using UHV RF sputtering.•Both Au and Pt diffuse to a great extent into CoSb3 leg after annealing.•An intermetallic compound (IMC) layer, approximately 320nm thick, forms at the interface of CoSb3/Ti after annealing.•The formation of the IMC layer at the CoSb3/Ti interface has little effect on the electrical properties.•Depositing a Ti thin layer onto CoSb3 via sputtering forms the IMC layer, enhancing the efficiency of CoSb3 TE modules. We report the microstructure and electrical properties of CoSb3 legs on which Au, Pt, and Ti are deposited by ultra-high-vacuum (UHV) radio frequency (RF) sputtering. After annealing, an intermetallic compound (IMC) layer, approximately 320nm thick, forms at the interface of CoSb3/Ti. This layer plays a significant role as a diffusion barrier in a CoSb3 thermoelectric (TE) module. The IMC layer has little effect on the electrical properties of CoSb3/Ti. However, no IMC layers were observed in CoSb3/Au and CoSb3/Pt, where Au and Pt diffused into the CoSb3 leg to a great depth. Our results demonstrate that a Ti layer on a CoSb3 leg deposited by a sputtering system is effective to form the IMC layer, preventing further diffusion of Ti and giving rise to enhance the efficiency of CoSb3 TE modules.