Atomic layer deposition of cobalt(II) oxide thin films from Co(BTSA)(2)(THF) and H2O

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Iivonen , T , Kaipio , M , Hatanpää , T , Mizohata , K , Meinander , K , Räisänen , J , Kim , J , Ritala , M & Leskelä , M 2019 , ' Atomic layer deposition of cobalt(II) oxide thin films from Co(BTSA)(2)(THF) and H2O ' , Journal of vacuum science & technology : an official journal of the American Vacuum Society , vol. 37 , no. 1 , 010908 . https://doi.org/10.1116/1.5066638

Title: Atomic layer deposition of cobalt(II) oxide thin films from Co(BTSA)(2)(THF) and H2O
Author: Iivonen, Tomi; Kaipio, Mikko; Hatanpää, Timo; Mizohata, Kenichiro; Meinander, Kristoffer; Räisänen, Jyrki; Kim, Jiyeon; Ritala, Mikko; Leskelä, Markku
Contributor: University of Helsinki, Department of Chemistry
University of Helsinki, Department of Chemistry
University of Helsinki, Department of Chemistry
University of Helsinki, Materials Physics
University of Helsinki, Materials Physics
University of Helsinki, Department of Physics
University of Helsinki, Department of Chemistry
University of Helsinki, Department of Chemistry
Date: 2019-01
Language: eng
Number of pages: 12
Belongs to series: Journal of vacuum science & technology : an official journal of the American Vacuum Society
ISSN: 0734-2101
URI: http://hdl.handle.net/10138/308509
Abstract: In this work, we have studied the applicability of Co(BTSA)(2)(THF) [BTSA = bis(trimethylsilyl)amido] (THF = tetrahydrofuran) in atomic layer deposition (ALD) of cobalt oxide thin films. When adducted with THF, the resulting Co(BTSA)(2)(THF) showed good volatility and could be evaporated at 55 degrees C, which enabled film deposition in the temperature range of 75-250 degrees C. Water was used as the coreactant, which led to the formation of Co(II) oxide films. The saturative growth mode characteristic to ALD was confirmed with respect to both precursors at deposition temperatures of 100 and 200 degrees C. According to grazing incidence x-ray diffraction measurements, the films contain both cubic rock salt and hexagonal wurtzite phases of CoO. X-ray photoelectron spectroscopy measurements confirmed that the primary oxidation state of cobalt in the films is +2. The film composition was analyzed using time-of-flight elastic recoil detection analysis, which revealed the main impurities in the films to be H and Si. The Si impurities originate from the BTSA ligand and increased with increasing deposition temperature, which indicates that Co(BTSA)(2)(THF) is best suited for low-temperature deposition. To gain insight into the surface chemistry of the deposition process, an in situ reaction mechanism study was conducted using quadrupole mass spectroscopy and quartz crystal microbalance techniques. Based on the in situ experiments, it can be concluded that film growth occurs via a ligand exchange mechanism. Published by the AVS.
Subject: COBALT OXIDE
Thin film
reaction mechanism
TOF-ERDA
XPS
AFM
116 Chemical sciences
221 Nano-technology
114 Physical sciences
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