Formation and Properties of Nickel Contacts to Thermoelectric Materials Based on Bismuth and Antimony Chalcogenides

Procedures were suggested for preparing ohmic contacts by electroless Ni plating onto the surface of samples of thermoelectric materials based on bismuth and antimony chalcogenides. Nickel was deposited directly onto the sample surface and onto a Ni sublayer formed by ion plasma sputtering on the sample surface. The properties of the contacts are influenced by the roughness of the surface of thermoelectric material samples, by solutions used for decapping this surface, by the composition of electrolytes for electroless Ni plating, and by the presence of a Ni sublayer sputtered onto the sample surface. The Ni films up to 25 mu m thick, prepared by electroless plating, contained >= 96.73 wt % Ni. The resistivity of the films was <= 10.24 x 10(-8) omega m. The specific contact resistance was (1.50-2.86) x 10(-9) omega m(2). The films obtained on thermoelectric material samples by Ni plating from a NaBH4-based electrolyte onto a Ni sublayer sputtered onto these samples showed the highest adhesion strength, 14.62-14.83 MPa.