Atomic layer deposition of Zr-sandwiched ZnO thin films for transparent thermoelectrics

Funding Information: The authors acknowledge the financial support from the Academy of Finland projects 319018 eVapor and 329406 CarbonSurf as well as from the Photonics Flagship PREIN. T.K. acknowledges the doctoral school of Aalto University School of Electrical Engineering, Walter Ahlström foundation and Waldemar Von Frenckell foundation for financial support. C.T. acknowledges the financial support of the Yrjö, Vilho ja Kalle Väisälä Fund and of the Finnish Academy of Sciences and Letters. The experimental work was carried out in Micronova, the nanofabrication facility of Aalto University. Edgar Maiorov is acknowledged for ALD equipment support. Dr Vladimir Kornienko is acknowledged for helping with the transmission measurement. The characterization by XRD, TEM and FIB was carried out in the Nanomicroscopy Center of Aalto University. Funding Information: The authors acknowledge the financial support from the Academy of Finland projects 319018 eVapor and 329406 CarbonSurf as well as from the PhotonicsFlagship PREIN. T.K. acknowledges the doctoral school of Aalto University School of Electrical Engineering, Walter Ahlström foundation and Waldemar Von Frenckell foundation for financial support. C.T. acknowledges the financial support of the Yrjö, Vilho ja Kalle Väisälä Fund and of the Finnish Academy of Sciences and Letters. The experimental work was carried out in Micronova, the nanofabrication facility of Aalto University. Edgar Maiorov is acknowledged for ALD equipment support. Dr Vladimir Kornienko is acknowledged for helping with the transmission measurement. The characterization by XRD, TEM and FIB was carried out in the Nanomicroscopy Center of Aalto University. Publisher Copyright: © 2022 The Author(s). Published by IOP Publishing Ltd.Atomic layer deposited (ALD) transparent thermoelectric materials enable the introduction of energy harvesting and sensing devices onto surfaces of various shapes and sizes in imperceptible manner. Amongst these materials, ZnO has shown promising results in terms of both thermoelectric and optical characteristics. The thermoelectric performance of ZnO can be further optimized by introducing extrinsic doping, to the realization of which ALD provides excellent control. Here, we explore the effects of sandwiching of ZrO2 layers with ZnO on glass substrates. The room-temperature thermoelectric power factor is maximised at 116μW m−1 K−2 with samples containing a 2% nominal percentage of ZrO2. The addition of ZrO2 layers is further shown to reduce the thermal conductivity, resulting in a 20.2% decrease from the undoped ZnO at 2% doping. Our results contribute to increasing the understanding of the effects of Zr inclusion in structural properties and growth of ALD ZnO, as well as the thermal and thermoelectric properties of Zr-doped ZnO films in general.Peer reviewe