Homoleptic zirconium amidates: single source precursors for the aerosol-assisted chemical vapour deposition of ZrO2

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Abstract

We report the development of a true single source precursor (i.e. without any need for an exogenous source of oxygen) for the growth of zirconia thin films by aerosol-assisted chemical vapour deposition (AACVD) using an original family of zirconium(iv) amidate derivatives, which are easily prepared by protonolysis of [Zr(NMe2)4] with the free amide pro-ligands. In all but one case the reactions resulted in the isolation of the corresponding homoleptic eight-coordinate zirconium(iv)tetrakis(amidato) derivatives. Three of these species along with a tris(amidato)dimethylamido zirconium(iv) derivative have been characterised by single crystal X-ray diffraction analysis. The materials potential of the homoleptic compounds was identified through the application of design criteria derived from consideration of the existing knowledge base relating to the pyrolysis of wholly organic amides. In this manner the thermal decomposition of the homoleptic derivatives benefits from facile, molecularly imposed pyrolysis pathways, which provide for the privileged generation of volatile small molecule by-products and the production of contaminant-free solid oxide material. Thermogravimetric analysis, in conjunction with NMR spectroscopic analysis of the volatile products resulting from their thermal decomposition, indicated the potential of the homoleptic species as exquisite single source precursors to ZrO2 at moderate temperatures. The compound bearing both N- and C-iso-propyl substituents was, thus, applied as a true single source precursor under ambient pressure AACVD conditions. The resultant films, deposited on either SiO2-coated glass or quartz substrates, are smooth and comprise small and densely packed crystalline particulates that are shown by XRD to be primarily cubic ZrO2. Compositional analysis by X-ray photoelectron spectroscopy (XPS) revealed that the oxygen delivered, and the decomposition pathway provided, by the amidate ligand structure yields ZrO2 films which, though slightly sub-stoichiometric (ZrO1.8-1.9), contain undetectable levels of carbon incorporation.

LanguageEnglish
Pages10731-10739
Number of pages9
JournalJournal of Materials Chemistry C
Volume4
Issue number45
DOIs
StatusPublished - 7 Dec 2016

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Aerosols
Zirconium
Chemical vapor deposition
Pyrolysis
Derivatives
Amides
Bearings (structural)
Ligands
Oxygen
Quartz
Spectroscopic analysis
Zirconia
Oxides
X ray diffraction analysis
Byproducts
Thermogravimetric analysis
Carbon
X ray photoelectron spectroscopy
Nuclear magnetic resonance
Single crystals

ASJC Scopus subject areas

  • Chemistry(all)
  • Materials Chemistry

Cite this

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title = "Homoleptic zirconium amidates: single source precursors for the aerosol-assisted chemical vapour deposition of ZrO2",
abstract = "We report the development of a true single source precursor (i.e. without any need for an exogenous source of oxygen) for the growth of zirconia thin films by aerosol-assisted chemical vapour deposition (AACVD) using an original family of zirconium(iv) amidate derivatives, which are easily prepared by protonolysis of [Zr(NMe2)4] with the free amide pro-ligands. In all but one case the reactions resulted in the isolation of the corresponding homoleptic eight-coordinate zirconium(iv)tetrakis(amidato) derivatives. Three of these species along with a tris(amidato)dimethylamido zirconium(iv) derivative have been characterised by single crystal X-ray diffraction analysis. The materials potential of the homoleptic compounds was identified through the application of design criteria derived from consideration of the existing knowledge base relating to the pyrolysis of wholly organic amides. In this manner the thermal decomposition of the homoleptic derivatives benefits from facile, molecularly imposed pyrolysis pathways, which provide for the privileged generation of volatile small molecule by-products and the production of contaminant-free solid oxide material. Thermogravimetric analysis, in conjunction with NMR spectroscopic analysis of the volatile products resulting from their thermal decomposition, indicated the potential of the homoleptic species as exquisite single source precursors to ZrO2 at moderate temperatures. The compound bearing both N- and C-iso-propyl substituents was, thus, applied as a true single source precursor under ambient pressure AACVD conditions. The resultant films, deposited on either SiO2-coated glass or quartz substrates, are smooth and comprise small and densely packed crystalline particulates that are shown by XRD to be primarily cubic ZrO2. Compositional analysis by X-ray photoelectron spectroscopy (XPS) revealed that the oxygen delivered, and the decomposition pathway provided, by the amidate ligand structure yields ZrO2 films which, though slightly sub-stoichiometric (ZrO1.8-1.9), contain undetectable levels of carbon incorporation.",
author = "Catherall, {Amanda L.} and Hill, {Michael S.} and Johnson, {Andrew L.} and Gabriele Kociok-Kohn and Mahon, {Mary F.}",
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T1 - Homoleptic zirconium amidates

T2 - Journal of Materials Chemistry C

AU - Catherall,Amanda L.

AU - Hill,Michael S.

AU - Johnson,Andrew L.

AU - Kociok-Kohn,Gabriele

AU - Mahon,Mary F.

PY - 2016/12/7

Y1 - 2016/12/7

N2 - We report the development of a true single source precursor (i.e. without any need for an exogenous source of oxygen) for the growth of zirconia thin films by aerosol-assisted chemical vapour deposition (AACVD) using an original family of zirconium(iv) amidate derivatives, which are easily prepared by protonolysis of [Zr(NMe2)4] with the free amide pro-ligands. In all but one case the reactions resulted in the isolation of the corresponding homoleptic eight-coordinate zirconium(iv)tetrakis(amidato) derivatives. Three of these species along with a tris(amidato)dimethylamido zirconium(iv) derivative have been characterised by single crystal X-ray diffraction analysis. The materials potential of the homoleptic compounds was identified through the application of design criteria derived from consideration of the existing knowledge base relating to the pyrolysis of wholly organic amides. In this manner the thermal decomposition of the homoleptic derivatives benefits from facile, molecularly imposed pyrolysis pathways, which provide for the privileged generation of volatile small molecule by-products and the production of contaminant-free solid oxide material. Thermogravimetric analysis, in conjunction with NMR spectroscopic analysis of the volatile products resulting from their thermal decomposition, indicated the potential of the homoleptic species as exquisite single source precursors to ZrO2 at moderate temperatures. The compound bearing both N- and C-iso-propyl substituents was, thus, applied as a true single source precursor under ambient pressure AACVD conditions. The resultant films, deposited on either SiO2-coated glass or quartz substrates, are smooth and comprise small and densely packed crystalline particulates that are shown by XRD to be primarily cubic ZrO2. Compositional analysis by X-ray photoelectron spectroscopy (XPS) revealed that the oxygen delivered, and the decomposition pathway provided, by the amidate ligand structure yields ZrO2 films which, though slightly sub-stoichiometric (ZrO1.8-1.9), contain undetectable levels of carbon incorporation.

AB - We report the development of a true single source precursor (i.e. without any need for an exogenous source of oxygen) for the growth of zirconia thin films by aerosol-assisted chemical vapour deposition (AACVD) using an original family of zirconium(iv) amidate derivatives, which are easily prepared by protonolysis of [Zr(NMe2)4] with the free amide pro-ligands. In all but one case the reactions resulted in the isolation of the corresponding homoleptic eight-coordinate zirconium(iv)tetrakis(amidato) derivatives. Three of these species along with a tris(amidato)dimethylamido zirconium(iv) derivative have been characterised by single crystal X-ray diffraction analysis. The materials potential of the homoleptic compounds was identified through the application of design criteria derived from consideration of the existing knowledge base relating to the pyrolysis of wholly organic amides. In this manner the thermal decomposition of the homoleptic derivatives benefits from facile, molecularly imposed pyrolysis pathways, which provide for the privileged generation of volatile small molecule by-products and the production of contaminant-free solid oxide material. Thermogravimetric analysis, in conjunction with NMR spectroscopic analysis of the volatile products resulting from their thermal decomposition, indicated the potential of the homoleptic species as exquisite single source precursors to ZrO2 at moderate temperatures. The compound bearing both N- and C-iso-propyl substituents was, thus, applied as a true single source precursor under ambient pressure AACVD conditions. The resultant films, deposited on either SiO2-coated glass or quartz substrates, are smooth and comprise small and densely packed crystalline particulates that are shown by XRD to be primarily cubic ZrO2. Compositional analysis by X-ray photoelectron spectroscopy (XPS) revealed that the oxygen delivered, and the decomposition pathway provided, by the amidate ligand structure yields ZrO2 films which, though slightly sub-stoichiometric (ZrO1.8-1.9), contain undetectable levels of carbon incorporation.

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