High-Efficiency Thermoelectric 2D Tellurium Devices with Accumulation-type Metal-to-Semiconductor Contacts

The paradigm of a good thermal electrical material is usually a heavily doped narrow bandgap semiconductor with good electrical conductivity and low thermal conductivity. Bulk Te has been theoretically predicted and experimentally demonstrated to be an outstanding thermoelectric material. Recent achievements in growing high quality 2D Te films allow us to explore the thermoelectric performance of 2D Te. Using nano-fabricated heater and thermometer, we were able to measure the room temperature Seebeck coefficient and power factor of 0.41 mV/K and 31.7 μW/cm●K. Using the thermal conductivity of bulk Te, we can estimate the lower bound of ZT value to be ~0.32 at 300 K, whereas the true ZT value should be much higher considering the suppression of thermal conductivity in thin films. The details of film thickness dependence are on-going and will be reported. Thermoelectrical current mapping was performed with a laser heater, and we found high work function metals such as Palladium can form rare accumulation type metal-to-semiconductor contacts to Te, which allows thermoelectrically generated carriers to be collected more efficiently. High-performance thermoelectric Te devices will have broad applications for energy harvesting or as a Peltier cooler in microsystems.