Fabrication of ZnO-based thermoelectric micro-devices by electrodeposition

In order to fabricate micro-thermoelectric devices, ZnO films were prepared via electrodeposition, and the effect of deposition condition on the films was investigated. It was found that morphology and crystallinity of ZnO films were strongly affected by applied potential, bath composition and bath temperature, and using the optimized condition, ZnO-based micro-thermoelectric devices were fabricated and device performance was evaluated. For electrodeposition, acetate ion was added into the bath to prevent several drawbacks such as formation of pits and cracks. From the solution containing zinc nitrate and sodium acetate as a source of acetate ion, ZnO films were electrodeposited. The films with smooth morphology and sufficient adhesion strength were obtained at −0.9 V vs. Ag/AgCl with the addition of 10 mmolL−¹ sodium acetate. The films with higher crystallinity and thermoelectric properties were obtained from the bath with higher temperature of 80^◦C. The micro-thermoelectric device, which consisted of four arrays and each array had 55 pairs of thermoelectric elements, was fabricated and it generated 0.73 nW as maximum power. The power density was approximately 40 times larger than that of the ZnO thin films, which demonstrated that electrodeposited ZnO could be applied to thermoelectric micro-devices.