Technology and Investigation of Ohmic Contacts to Thermoelectric Materials

Abstract

Technology is developed, materials and regimes of the fabrication of ohmic contacts to the effective thermoelectric materials Bi2Te2.8Se0.2 (n-type) and Bi0.5Sb1.5Te3 (p-type) are determined. Ohmic contacts were obtained by the vacuum deposition of nickel. Factors determining adhesion strength and resistivity of fabricated contacts are determined. Process of surface preparation of the thermoelectric materials before the ohmic contact deposition is optimized during the technology development. The use of electrochemical polishing, ultrasound treatment, finish cleaning in toluene and isopropyl alcohol vapor, and annealing in vacuum allowed achieving stable results in the formation of contacts. It was shown that contacts fabricated using of electron-beam evaporation of nickel possess maximum adhesion strength of 18–19 N/mm. It was found that high adhesion is caused by the existence of transition layer in the metal-thermoelectric material contact range, formed due to the interaction of metal with the components of thermoelectric material. Proposed technology allows obtaining ohmic contacts with the resistance of the unit area not exceeding 10−10 Ohmm.