Microstructure and Thermoelectric Properties of Zn_1–xAg_xSb Thin Films Grown by Single-Target Magnetron Sputtering

Thermoelectric thin films could potentially power the Internet of Things devices including microsized sensors and actuators without the need of battery replacement. Zinc antimonides are among the cheapest high-performance thermoelectric materials, and here we demonstrate the use of a ZnSb phase single target to deposit Zn1–xAgxSb (x = 0, 0.01, and 0.02) thin films on fused silica substrates via direct current magnetron sputtering. In order to achieve optimal thermoelectric properties, the effects of the annealing temperature, Ar gas pressure, and deposition time on the film microstructure were investigated, and Ag doping was introduced in the Zn–Sb binary system. There is a clear decrease in the electrical resistivity due to Ag doping, and unlike the undoped ZnSb thin film, the Ag-doped ZnSb thin films show a change in the film texture when varying the deposition time. A high power factor value of 14.9 μV cm–1 K–2 at 525 K and a conservatively estimated maximum zT of ∼0.5 at 575 K using the thermal conductivity of the bulk material are obtained in the Ag-doped thin film. The highest estimated value of average zT is 0.16 for a temperature range between 300 and 575 K. Thus, the present work demonstrates a simple synthesis route for growing high-performance thermoelectric ZnSb thin films.