Effect of Surface Roughness of Substrate on Adhesion Strength of Ni/Bi2(Te, Se)3 Interface

Nickle (Ni) is mostly used as the barrier layer at the thermoelectric solder joints to prevent the electrode material and solder from entering the thermoelectric material substrate. However, the Ni layer will peel off from the substrate due to the poor adhesion strength of Ni/Bi2(Te, Se)3 interface. The present study attempted to improve the adhesion strength of the Ni coating by changing the micro-etching time of the substrate in the micro-etching solution and explored the influence of the surface roughness on the adhesion strength of the Ni coating. In addition, we chose a deposition method that combines electroplating and electroless plating on the surface of the Bi2(Te, Se)3 substrate. It revealed that with the increase of micro-etching time, the surface roughness of the substrate becomes larger, and the grain size of the Ni coating increases. Moreover, with the increase of the Bi2(Te, Se)3 substrate surface roughness, the adhesion strength of Ni/Bi2(Te, Se)3 interface increases at first and then decreases. It suggests that the roughness of the substrate surface has remarkable influences on the adhesion strength of Ni/Bi2(Te, Se)3 interface.