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Role of Temperature, Pressure, and Surface Oxygen Migration in the Initial Atomic Layer Deposition of HfO2on Anatase TiO2(101)

D'Acunto, Giulio LU ; Jones, Rosemary LU ; Pérez Ramírez, Lucía ; Shayesteh, Payam LU ; Kokkonen, Esko LU orcid ; Rehman, Foqia LU ; Lim, Florence ; Bournel, Fabrice ; Gallet, Jean Jacques and Timm, Rainer LU orcid , et al. (2022) In Journal of Physical Chemistry C 126(29). p.12210-12221
Abstract

The atomic layer deposition of HfO2on a TiO2(101) surface from tetrakis(dimethylamido)hafnium and water is investigated using a combination of in situ vacuum X-ray photoelectron spectroscopy (XPS) and time-resolved ambient pressure XPS. Precursor pressures and surface temperature are tuned as to map the space state of the deposition. In the initial stages of ALD, a reaction mechanism based on dissociative adsorption dominates over a classic ligand exchange mechanism, typically evoked when metal-amido complexes and water are used as the precursors for metal oxide ALD. Surface species, including a dimethyl ammonium ion and an imine, are identified. It is found that they can be formed only if the active role of the... (More)

The atomic layer deposition of HfO2on a TiO2(101) surface from tetrakis(dimethylamido)hafnium and water is investigated using a combination of in situ vacuum X-ray photoelectron spectroscopy (XPS) and time-resolved ambient pressure XPS. Precursor pressures and surface temperature are tuned as to map the space state of the deposition. In the initial stages of ALD, a reaction mechanism based on dissociative adsorption dominates over a classic ligand exchange mechanism, typically evoked when metal-amido complexes and water are used as the precursors for metal oxide ALD. Surface species, including a dimethyl ammonium ion and an imine, are identified. It is found that they can be formed only if the active role of the TiO2(101) surface is taken into consideration. The temperature of the surface enhances the formation of these species based on an insertion reaction of a hydrogen atom, which then assists the formation of more than the expected monolayer of HfO2. A HfO2overlayer is produced already during the first half-cycle, enabled by a reduction of the TiO2support. Dosing water at high pressure allows hydroxyl formation, which marks the transition toward a well-described ligand exchange reaction type. From the experiments performed, we find that the ALD of HfO2at room temperature, performed at high pressure, is mainly based on dissociation and that no side reaction occurs. These insights into the ALD reaction mechanism highlight how in situ studies can help understand how deposition parameters affect the growth of HfO2and how the ALD model for transition metal oxide formation from amido complexes and water can be extended.

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organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Journal of Physical Chemistry C
volume
126
issue
29
pages
12 pages
publisher
The American Chemical Society (ACS)
external identifiers
  • scopus:85135565298
ISSN
1932-7447
DOI
10.1021/acs.jpcc.2c02683
language
English
LU publication?
yes
id
72346e1a-da6a-4d46-bc97-29534685e3e6
date added to LUP
2022-10-28 14:50:48
date last changed
2023-11-21 12:44:14
@article{72346e1a-da6a-4d46-bc97-29534685e3e6,
  abstract     = {{<p>The atomic layer deposition of HfO<sub>2</sub>on a TiO<sub>2</sub>(101) surface from tetrakis(dimethylamido)hafnium and water is investigated using a combination of in situ vacuum X-ray photoelectron spectroscopy (XPS) and time-resolved ambient pressure XPS. Precursor pressures and surface temperature are tuned as to map the space state of the deposition. In the initial stages of ALD, a reaction mechanism based on dissociative adsorption dominates over a classic ligand exchange mechanism, typically evoked when metal-amido complexes and water are used as the precursors for metal oxide ALD. Surface species, including a dimethyl ammonium ion and an imine, are identified. It is found that they can be formed only if the active role of the TiO<sub>2</sub>(101) surface is taken into consideration. The temperature of the surface enhances the formation of these species based on an insertion reaction of a hydrogen atom, which then assists the formation of more than the expected monolayer of HfO<sub>2</sub>. A HfO<sub>2</sub>overlayer is produced already during the first half-cycle, enabled by a reduction of the TiO<sub>2</sub>support. Dosing water at high pressure allows hydroxyl formation, which marks the transition toward a well-described ligand exchange reaction type. From the experiments performed, we find that the ALD of HfO<sub>2</sub>at room temperature, performed at high pressure, is mainly based on dissociation and that no side reaction occurs. These insights into the ALD reaction mechanism highlight how in situ studies can help understand how deposition parameters affect the growth of HfO<sub>2</sub>and how the ALD model for transition metal oxide formation from amido complexes and water can be extended.</p>}},
  author       = {{D'Acunto, Giulio and Jones, Rosemary and Pérez Ramírez, Lucía and Shayesteh, Payam and Kokkonen, Esko and Rehman, Foqia and Lim, Florence and Bournel, Fabrice and Gallet, Jean Jacques and Timm, Rainer and Schnadt, Joachim}},
  issn         = {{1932-7447}},
  language     = {{eng}},
  month        = {{07}},
  number       = {{29}},
  pages        = {{12210--12221}},
  publisher    = {{The American Chemical Society (ACS)}},
  series       = {{Journal of Physical Chemistry C}},
  title        = {{Role of Temperature, Pressure, and Surface Oxygen Migration in the Initial Atomic Layer Deposition of HfO<sub>2</sub>on Anatase TiO<sub>2</sub>(101)}},
  url          = {{http://dx.doi.org/10.1021/acs.jpcc.2c02683}},
  doi          = {{10.1021/acs.jpcc.2c02683}},
  volume       = {{126}},
  year         = {{2022}},
}