The Surface Preparation of Thermoelectric Materials for Deposition of Thin-Film Contact Systems

Abstract

The method of mechanical treatment of thermoelectric materials Bi₂Te_2.8Se_0.2 (0.14 wt % of CdCl₂), Bi_0.5Sb_1.5Te₃ (2 wt % of Te and 0.14 wt % of TeI₄), PbTe (0.2 wt % of PbI₂ and 0.3 wt % of Ni), and GeTe (7.4 wt % of Bi) with low microhardness (25–70 kg/mm²) is proposed. The average surface roughness about 20 nm was obtained. The methods and regimes of surface cleaning before the deposition of thin films were determined. The thin-film Ni contacts were formed by ion-plasma deposition on the samples of thermoelectric materials with different surface roughness. The adhesion strength of contacts was measured by the method of uniform normal tear. The study results allow us to determine the required level of mechanical treatment of surface, which depends on the thickness of the formed thin films. It was shown that value of the adhesion strength of Ni contacts formed to the thermoelectric materials is more than 11.5 MPa. This corresponds to criterion of mechanical strength of contacts in the thermoelements. As study result of the electrical resistance, it was found that the contact resistance of Ni films formed on thermoelectric materials is less than 10^–9 Ω m².