Issue 38, 2020

Understanding KOtBu in atomic layer deposition – in situ mechanistic studies of the KNbO3 growth process

Abstract

Functional coatings based on alkali metals have become increasingly attractive in the current shift towards sustainable technologies. While lithium-based compounds have a natural impact on batteries, other alkali metal compounds are important as replacements for toxic materials in a range of electronic devices. This is especially true for potassium, being a major component in e.g. KxNa1−xNbO3 (KNN) and KTaxNb1−xO3 (KTN), with hope to replace Pb(ZrxTi1−x)O3 (PZT) in piezo-/ferroelectric and electrooptic devices. ALD facilitates functional conformal coatings at deposition temperatures far below what is reported using other techniques and with excellent compositional control. The ALD growth of potassium-containing films using KOtBu has, however, been unpredictable. Untraditional response to the pulse composition and precursor dose, severe reproducibility issues, and very high growth per cycle are some of the puzzling features of these processes. In this article, we shed light on the growth behavior of KOtBu in ALD by in situ quartz crystal microbalance and Fourier transform infrared spectroscopy studies. We study the precursor's behavior in the technologically interesting KNbO3-process, showing how the potassium precursor strongly affects the growth of other cation precursors. We show that the strong hygroscopic nature of the intermediary potassium species has far-reaching implications throughout the growth. This helps not only to enhance the understanding of alkali metal containing compounds’ growth in ALD, but also to provide the means to control the growth of novel sustainable technological materials.

Graphical abstract: Understanding KOtBu in atomic layer deposition – in situ mechanistic studies of the KNbO3 growth process

Supplementary files

Article information

Article type
Paper
Submitted
01 Jul 2020
Accepted
03 Ago 2020
First published
04 Ago 2020

Dalton Trans., 2020,49, 13233-13242

Author version available

Understanding KOtBu in atomic layer deposition – in situ mechanistic studies of the KNbO3 growth process

H. H. Sønsteby, V. A.-L. K. Killi, T. A. Storaas, D. Choudhury, J. W. Elam, H. Fjellvåg and O. Nilsen, Dalton Trans., 2020, 49, 13233 DOI: 10.1039/D0DT02324H

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