Surface Preparation and Investigation of Ohmic Film Contacts Formed by Various Methods to Thermoelements

Abstract

Methods were proposed and criteria were established for surface preparation of nanostructured thermoelectric materials for deposition of thin and thick film ohmic contacts. The parameters of the mechanical and chemical methods of thermoelectric material surface treatment before the deposition of contacts were established. The roughness and morphology of the surface of thermoelectric material samples and the films obtained have been studied. Criteria and optimal values of surface roughness of thermoelectric materials were established. The conditions of obtaining thin and thick film contacts were determined. Thin film contacts (thickness up to 300 nm) were obtained by magnetron sputtering of Ni. Thick film contacts were formed by chemical and electrochemical deposition of Ni. The obtained films contained various amounts of Ni. The electrical resistivity of Ni films obtained by chemical deposition was significantly higher than that of Ni films obtained by electrochemical deposition. The specific contact resistance of the metal–thermoelectric material system in the case of deposition of Ni films by magnetron sputtering was the smallest among the considered samples. And in the case of forming contacts by chemical deposition, it is comparable to that for Ni films formed by electrochemical deposition. The adhesion strength of Ni films obtained by various methods has high values exceeding the industry standard for film coatings in microelectronics. All obtained ohmic contacts satisfy the requirements for the construction of the efficient thermoelements by the electrical properties and adhesive strength.