Oxidant-Dependent Thermoelectric Properties of Undoped ZnO Films by Atomic Layer Deposition

Abstract
Extraordinary oxidant-dependent changes in the thermoelectric properties of undoped ZnO thin films deposited by atomic layer deposition (ALD) have been observed. Specifically, deionized water and ozone oxidants are used in the growth of ZnO by ALD using diethylzinc as a zinc precursor. No substitutional atoms have been added to the ZnO films. By using ozone as an oxidant instead of water, a thermoelectric power factor (σS) of 5.76 × 10 W m K is obtained at 705 K for undoped ZnO films. In contrast, the maximum power factor for the water-based ZnO film is only 2.89 × 10 W m K at 746 K. Materials analysis results indicate that the oxygen vacancy levels in the water- and ozone-grown ZnO films are essentially the same, but the difference comes from Zn-related defects present in the ZnO films. The data suggest that the strong oxidant effect on thermoelectric performance can be explained by a mechanism involving point defect-induced differences in carrier concentration between these two oxides and a self-compensation effect in water-based ZnO due to the competitive formations of both oxygen and zinc vacancies. This strong oxidant effect on the thermoelectric properties of undoped ZnO films provides a pathway to improve the thermoelectric performance of this important material.

Citation
Kim H, Wang Z, Hedhili MN, Wehbe N, Alshareef HN (2017) Oxidant-Dependent Thermoelectric Properties of Undoped ZnO Films by Atomic Layer Deposition. Chemistry of Materials 29: 2794–2802. Available: http://dx.doi.org/10.1021/acs.chemmater.6b04654.

Acknowledgements
Research reported in this publication was supported by King Abdullah University of Science and Technology (KAUST).

Publisher
American Chemical Society (ACS)

Journal
Chemistry of Materials

DOI
10.1021/acs.chemmater.6b04654

Additional Links
http://pubs.acs.org/doi/abs/10.1021/acs.chemmater.6b04654

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