Role of the Coreactant on the Dual-Source Behavior of Lithium Hexamethyldisilazide for ALD Li-Containing Films.

Autor: Pieters MJ; Department of Applied Physics and Science Education, Eindhoven University of Technology, Eindhoven 5600 MB, The Netherlands., Bartel L; Department of Applied Physics and Science Education, Eindhoven University of Technology, Eindhoven 5600 MB, The Netherlands., van Helvoirt C; Department of Applied Physics and Science Education, Eindhoven University of Technology, Eindhoven 5600 MB, The Netherlands., Creatore M; Department of Applied Physics and Science Education, Eindhoven University of Technology, Eindhoven 5600 MB, The Netherlands.; Eindhoven Institute of Renewable Energy Systems (EIRES), PO Box 513, Eindhoven, 5600 MB, The Netherlands.
Jazyk: angličtina
Zdroj: The journal of physical chemistry. C, Nanomaterials and interfaces [J Phys Chem C Nanomater Interfaces] 2024 Nov 07; Vol. 128 (46), pp. 19638-19647. Date of Electronic Publication: 2024 Nov 07 (Print Publication: 2024).
DOI: 10.1021/acs.jpcc.4c05987
Abstrakt: Atomic layer deposition (ALD) of Li-containing thin films is deemed as highly relevant for the development of next-generation Li-ion batteries. Lithium hexamethyldisilazide (LiHMDS), as Li-containing precursor, is preferred over the widely used lithium tert -butoxide because of its lower melting point of 70 °C. However, the presence of silyl groups in the LiHMDS chemical structure can result in the undesired incorporation of Si in the film. Therefore, understanding the reaction mechanism of LiHMDS is required to control its dual-source behavior and grow Si-free Li-containing thin films. For this purpose LiHMDS was combined with O 2 plasma or water as coreactant. In situ spectroscopic ellipsometry (SE) and X-ray photoelectron spectroscopy (XPS) revealed that using O 2 plasma as coreactant results in linear growth and Si-containing films, whereas using H 2 O as coreactant leads to fast, nonsurface-reaction-limited growth and Si-free films. To shed light on the role of the coreactant on the reaction mechanism of LiHMDS, in situ studies by time-resolved quadrupole mass spectrometry (QMS) were performed on the O 2 plasma and H 2 O-based ALD processes. Measurements taken during full ALD cycles and half-cycles were carefully compared to identify which half-cycle surface reaction products lead to silicon incorporation in the film. The QMS results of the LiHMDS + H 2 O process showed that LiHMDS both chemisorbs and physisorbs. Furthermore, it is concluded that Si incorporation occurs during the O 2 plasma step, when the physisorbed ligands are combusted and Si-containing products are redeposited. This work also demonstrates that the incorporated Si can be abstracted from the film by means of a H 2 plasma step following the O 2 plasma step. These insights on the role of the coreactant in the synthesis of Li-containing films contribute to the development of LiHMDS-based ALD processes for Li-ion battery applications.
Competing Interests: The authors declare no competing financial interest.
(© 2024 The Authors. Published by American Chemical Society.)
Databáze: MEDLINE
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