Enhanced thermoelectricity at the ultra-thin film limit

At the ultra-thin film limit, quantum confinement strongly improves the thermoelectric figure of merit in materials such as Sb2Te3 and Bi2Te3. These high quality films have only been realized using well controlled techniques such as molecular beam epitaxy. We report a twofold increase in the Seebeck coefficient for both p-type Sb2Te3 and n-type Bi2Te3 using thermal co-evaporation, an affordable approach. At the thick film limit greater than 100nm, their Seebeck coefficients are around 100 mu V/K, similar to the results obtained in other works. When the films are thinner than 50nm, the Seebeck coefficient increases to about 500 mu V/K. With the Seebeck coefficient similar to 1mV/K and an estimate ZT similar to 0.6, this pair of materials presents the first step toward a practical micro-cooler at room temperature.