Probing the Chemistry of Alumina Atomic Layer Deposition Using Operando Surface-Enhanced Raman Spectroscopy

Sicelo S. Masango, Ryan A. Hackler, Anne Isabelle Henry, Michael O. McAnally, George C Schatz, Peter C Stair, Richard P. Van Duyne

Research output: Contribution to journalArticle

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Abstract

This work demonstrates for the first time the capability of measuring surface vibrational spectra for adsorbates during atomic layer deposition (ALD) reactions using operando surface-enhanced Raman spectroscopy (SERS). We use SERS to study alumina ALD growth at 55°C on bare silver film-over nanosphere (AgFON) substrates as well as AgFONs functionalized with thiol self-assembled monolayers (SAMs). On bare AgFONs, we observe the growth of Al-C stretches, symmetric C-H and asymmetric C-H stretches during the trimethylaluminum (TMA) dose half-cycle, and their subsequent decay after dosing with H2O. Al-C and C-H vibrational modes decay in intensity with time even without H2O exposure providing evidence that residual H2O in the ALD chamber reacts with -CH3 groups on AgFONs. The observed Al-C stretches are attributed to TMA dimeric species on the AgFON surface in agreement with density functional theory (DFT) studies. We observe Al-C stretches and no thiol vibrational frequency shifts after dosing TMA on AgFONs functionalized with toluenethiol and benzenethiol SAMs. Conversely, we observe thiol vibrational frequency shifts and no Al-C stretches for AgFONs functionalized with 4-mercaptobenzoic acid and 4-mercaptophenol SAMs. Lack of observed Al-C stretches for COOH- and OH-terminated SAMs is explained by the spacing of Al-(CH3)x groups from the SERS substrate. TMA penetrates through SAMs and reacts directly with Ag for benzenethiol and toluenethiol SAMs and selectively reacts with the -COOH and -OH groups for 4-mercaptobenzoic acid and 4-mercaptophenol SAMs, respectively. The high sensitivity and chemical specificity of SERS provides valuable information about the location of ALD deposits with respect to the enhancing substrate. This information can be used to evaluate the efficacy of SAMs in blocking or allowing ALD deposition on metal surfaces. The ability to probe ALD reactions using SERS under realistic reaction conditions will lead to a better understanding of the mechanisms of ALD reactions.

Original languageEnglish
Pages (from-to)3822-3833
Number of pages12
JournalJournal of Physical Chemistry C
Volume120
Issue number7
DOIs
Publication statusPublished - Feb 25 2016

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Atomic layer deposition
Aluminum Oxide
Self assembled monolayers
atomic layer epitaxy
Raman spectroscopy
Alumina
aluminum oxides
chemistry
thiols
Vibrational spectra
Sulfhydryl Compounds
frequency shift
Substrates
acids
decay
Acids
Nanospheres
Surface reactions
vibrational spectra
surface reactions

ASJC Scopus subject areas

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

Cite this

Probing the Chemistry of Alumina Atomic Layer Deposition Using Operando Surface-Enhanced Raman Spectroscopy. / Masango, Sicelo S.; Hackler, Ryan A.; Henry, Anne Isabelle; McAnally, Michael O.; Schatz, George C; Stair, Peter C; Van Duyne, Richard P.

In: Journal of Physical Chemistry C, Vol. 120, No. 7, 25.02.2016, p. 3822-3833.

Research output: Contribution to journalArticle

Masango, Sicelo S. ; Hackler, Ryan A. ; Henry, Anne Isabelle ; McAnally, Michael O. ; Schatz, George C ; Stair, Peter C ; Van Duyne, Richard P. / Probing the Chemistry of Alumina Atomic Layer Deposition Using Operando Surface-Enhanced Raman Spectroscopy. In: Journal of Physical Chemistry C. 2016 ; Vol. 120, No. 7. pp. 3822-3833.
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