Alternative low-pressure surface chemistry of titanium tetraisopropoxide on oxidized molybdenum

Alexis M. Johnson, Peter C Stair

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

Titanium tetraisopropoxide (TTIP) is a precursor utilized in atomic layer depositions (ALDs) for the growth of TiO2. The chemistry of TTIP deposition onto a slightly oxidized molybdenum substrate was explored under ultrahigh vacuum (UHV) conditions with X-ray photoelectron spectroscopy. Comparison of the Ti(2p) and C(1s) peak areas has been used to determine the surface chemistry for increasing substrate temperatures. TTIP at a gas-phase temperature of 373 K reacts with a MoOx substrate at 373 K but not when the substrate is at 295 K, consistent with a reaction that proceeds via a Langmuir-Hinshelwood mechanism. Chemical vapor deposition was observed for depositions at 473 K, below the thermal decomposition temperature of TTIP and within the ALD temperature window, suggesting an alternative reaction pathway competitive to ALD. We propose that under conditions of low pressure and moderate substrate temperatures dehydration of the reacted precursor by nascent TiO2 becomes the dominant reaction pathway and leads to the CVD growth of TiO2 rather than a self-limiting ALD reaction. These results highlight the complexity of the chemistry of ALD precursors and demonstrate that changing the pressure can drastically alter the surface chemistry.

Original languageEnglish
Pages (from-to)29361-29369
Number of pages9
JournalJournal of Physical Chemistry C
Volume118
Issue number50
DOIs
Publication statusPublished - Dec 18 2014

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Molybdenum
Atomic layer deposition
atomic layer epitaxy
Surface chemistry
molybdenum
low pressure
titanium
Titanium
chemistry
Substrates
Chemical vapor deposition
Temperature
temperature
vapor deposition
Ultrahigh vacuum
Dehydration
dehydration
ultrahigh vacuum
thermal decomposition
Pyrolysis

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Electronic, Optical and Magnetic Materials
  • Surfaces, Coatings and Films
  • Energy(all)

Cite this

Alternative low-pressure surface chemistry of titanium tetraisopropoxide on oxidized molybdenum. / Johnson, Alexis M.; Stair, Peter C.

In: Journal of Physical Chemistry C, Vol. 118, No. 50, 18.12.2014, p. 29361-29369.

Research output: Contribution to journalArticle

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