Diffusion at interfaces of micro thermoelectric devices

A micro thermoelectric device consists of bonding layer, electrodes and thermoelectric thin films. At interfaces between metallic electrodes, solder materials and thermoelectric thin films in a micro thermoelectric device, diffusion occurs and degrades its performance and reliability. Ni layer is used as the diffusion barrier in a commercial device using bulk thermoelectric materials, but few studies have been conducted to examine the diffusion phenomenon in a micro thermoelectric device using thermoelectric thin films. In this study, n-type Bi2Te3 and p-type Bi0.5Sb1.5Te3 thin films were deposited by RF magnetron sputtering. Sn was considered as solder materials, and Au, Ag, Ni, Ta, TiN and TiW were used as diffusion barriers. According as increasing anneal temperature, we analyzed the diffusion characteristics at interfaces between solder materials and thermoelectric thin films. The cross section of interfaces was investigated using FE-SEM (field emission scanning electron microscope), and FE-TEM (field emission transmission electron microscope).