(Invited) Compact Telluride Films Prepared By Electrochemical Deposition and Their Applications for Integrated Micro- Thermoelectric Devices

Thermoelectric materials of Tellurium (Te) and its based compounds (binary Bi2Te3 and Sb2Te3, or ternary Bi2(TexSe1-x)3 and (BixSb1-x)2Te3) as the n-type and p-type materials, respectively), possess the best thermoelectric figure-of-merit in the temperature range of room temperature up to 200 °C. Preparing thick and compact Telluride films with thickness in the range of tens of micrometers by electrochemical deposition (ECD) allows to realize on-chip integration of thermoelectric devices. ECD offers additional advantages regarding up-scalability, cost effective processing, and compatibility with microelectromechanical systems processing. In our work, we firstly put efforts on growing thick and compact Telluride films for both n- and p- type materials by ECD technique. Secondly, various measurement techniques (in-situ and ex-situ) are utilized to characterize the thermoelectric transport properties, which are further analyzed to tune the ECD parameters to optimize the material properties. Thirdly, integrated micro- thermoelectric coolers (µTECs), with a leg pair packing density over 5000/cm2 are successfully fabricated by combining conventional techniques of ECD and photolithography. Long-term performance and stability of the as-fabricated µTECs are systematically studied using a CCD-based thermoreflectance imaging setup. Finally, model simulations based on finite-element method show consistency with the experimental results, indicating high quality thermoelectric materials (for both n and p legs) and negligible contact resistances in the as-fabricated µTECs.