Phase-controlled growth of cobalt oxide thin films by atomic layer deposition

Soonyoung Jung, Dip K. Nandi, Seungmin Yeo, Hyungjun Kim, Yujin Jang, Jong Seong Bae, Tae Eun Hong, Soo Hyun Kim

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11 Citations (Scopus)

Abstract

Cobalt oxide (CoO x ) thin films were deposited on thermally grown SiO 2 substrates by atomic layer deposition (ALD) using bis(1,4-di-iso-propyl-1,4-diazabutadiene)cobalt (C 16 H 32 N 4 Co) and oxygen (O 2 ) as reactants at deposition temperatures ranging from 125 to 300 °C. X-ray diffraction (XRD) and Raman spectroscopic analysis indicated that a mixed-phase oxide consisting of CoO and Co 3 O 4 was deposited at temperatures ranging from 125 to 250 °C. However, single-phase Co 3 O 4 was deposited above the deposition temperature of 275 °C. Further, analyses by Rutherford backscattering spectrometry, transmission electron microscopy, and selected area electron diffraction along with XRD and Raman spectroscopy revealed that the single-phase cobalt oxide film was stoichiometric crystalline (spinel structure) with negligible N and C impurities. The optical band gap of the single-phase Co 3 O 4 film was 1.98 eV and increased with decreasing deposition temperature. It was also shown that the mixed-phase cobalt oxide thin films could be converted into single-phase spinel Co 3 O 4 by annealing at 350 °C in O 2 ambient. It was further observed that the phase of the ALD-grown cobalt oxide thin film could be controlled by controlling the precursor or reactant pulsing condition. The study revealed that pure Co 3 O 4 phase could be grown at a relatively low temperature (250 °C) by using water vapor as a reactant. Therefore, this work systemically demonstrated several pathways to grow single-phase Co 3 O 4 by ALD using a novel metalorganic cobalt precursor.

Original languageEnglish
Pages (from-to)404-410
Number of pages7
JournalSurface and Coatings Technology
Volume337
DOIs
Publication statusPublished - 2018 Mar 15

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All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Surfaces, Coatings and Films
  • Materials Chemistry

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