Herein, enhancements in thermoelectric performance, both power factor and thermal stability, are exhibited by sandwiching HfO2 and TiO2 layers onto atomic layer deposited ZnO thin films. High temperature thermoelectric measurements from 300 to 450 K revealed an almost two-fold improvement in electrical conductivity for TiO2/ZnO (TZO) samples, primarily owing to increase in carrier concentration by Ti doping. On the other hand, HfO2/ZnO (HZO) achieved the highest power factor values owing to maintaining Seebeck coefficients comparable to pure ZnO. HZO also exhibited excellent stability after multiple thermal cycles, which has not been previously observed for pure or doped ZnO thin films. Such improvement in both thermoelectric properties and thermal stability of HZO can be attributed to a shift in crystalline orientation from a-axis to c-axis, as well as the high bond dissociation energy of Hf-O, stabilizing the ZnO structure. These unique properties exhibited by ALD HZO and TZO thin films pave the way for next generation transparent thermoelectric devices.
Clairvaux Felizco, J., Juntunen, T., Uenuma, M., Etula, J., Tossi, C., Ishikawa, Y., Tittonen, I., & Uraoka, Y. (Accepted/In press). Enhanced Thermoelectric Transport and Stability in Atomic Layer Deposited HfO2/ZnO and TiO2/ZnO Sandwiched Multilayer Thin Films. ACS Applied Materials and Interfaces. https://doi.org/10.1021/acsami.0c11439