Low-temperature molecular layer deposition using monifunctional aromatic precursors and ozone-based ring-opening reactions

Laura Svärd, Matti Putkonen, Eija Kenttä, Timo Sajavaara, Fabian Krahl, Maarit Karppinen, Kevin Van de Kerckhove, Christophe Detavernier, Pekka Simell

Research output: Contribution to journalArticleScientificpeer-review

3 Citations (Scopus)

Abstract

Molecular layer deposition (MLD) is an increasingly used deposition technique for producing thin coatings consisting of purely organic or hybrid inorganic-organic materials. When organic materials are prepared, low deposition temperatures are often required to avoid decomposition, thus causing problems with low vapor pressure precursors. Monofunctional compounds have higher vapor pressures than traditional bi- or trifunctional MLD precursors, but do not offer the required functional groups for continuing the MLD growth in subsequent deposition cycles. In this study, we have used high vapor pressure monofunctional aromatic precursors in combination with ozone-triggered ring-opening reactions to achieve sustained sequential growth. MLD depositions were carried out by using three different aromatic precursors in an ABC sequence, namely with TMA + phenol + O3, TMA + 3-(trifluoromethyl)phenol + O3, and TMA + 2-fluoro-4-(trifluoromethyl)benzaldehyde + O3. Furthermore, the effect of hydrogen peroxide as a fourth step was evaluated for all studied processes resulting in a four-precursor ABCD sequence. According to the characterization results by ellipsometry, infrared spectroscopy, and X-ray reflectivity, self-limiting MLD processes could be obtained between 75 and 150 °C with each of the three aromatic precursors. In all cases, the GPC (growth per cycle) decreased with increasing temperature. In situ infrared spectroscopy indicated that ring-opening reactions occurred in each ABC sequence. Compositional analysis using time-of-flight elastic recoil detection indicated that fluorine could be incorporated into the film when 3-(trifluoromethyl)phenol and 2-fluoro-4-(trifluoromethyl)benzaldehyde were used as precursors.
Original languageEnglish
Pages (from-to)9657-9665
Number of pages9
JournalLangmuir
Volume33
Issue number38
DOIs
Publication statusPublished - 2017
MoE publication typeA1 Journal article-refereed

Keywords

  • aromatic compounds
  • atomic layer deposition
  • characterization
  • decay (organic)
  • deposition
  • hybrid materials
  • hydrostatic pressure
  • infrared spectroscopy
  • inorganic coatings
  • negative ions
  • ozone
  • phenols
  • self assembly
  • temperature
  • vapor pressure

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