Here is a recent paper from Prof. Stairs and Prof. Van Duyne research groups at North Western University on using surface-enhanced Raman spectroscopy (SERS) for studying ALD growth for the first time. Thanks Vincent Vandalon for sending me this information!
- SERS overcomes the sensitivity limitations of normal Raman scattering because of excitation of localized surface plasmon resonances (LSPRs) that result in enhanced electromagnetic fields around noble metal nanostructures such as Ag, Au, and Cu.
- The high sensitivity and distance dependence of SERS make it possible to evaluate the location of ALD deposits with respect to the enhancing substrate.
The ALD system at Van Duyne Research Group at North Western University. The ALD reactor can monitor ALD surface reactions in-situ using SERS and quartz crystal microbalance. The reactor will be connected to a GC for in-situ catalytic studies. The GC is equipped with a Thermal Conductivity and Flame Ionization detector so both permanent gases and hydrocarbons can be detected. (Picture and information form Van Duyne Research Group page)
Prof. Richard P. Van Duyne is the discoverer of Surface-enhanced Raman Spectroscopy (1977), the inventor of Nanosphere Lithography (1995) and Localized Surface Plasmon Resonance Spectroscopy (2000). More information can be found here.
Prof. Richard P. Van Duyne
Probing the Chemistry of Alumina Atomic Layer Deposition Using Operando Surface-Enhanced Raman Spectroscopy
Sicelo Simon Masango, Ryan A. Hackler, Anne-Isabelle Henry, Michael O. McAnally, George C. Schatz, Peter C. Stair, and Richard P. Van DuyneJ. Phys. Chem. C, Just Accepted Manuscript
DOI: 10.1021/acs.jpcc.5b11487
Publication Date (Web): January 28, 2016
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 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.
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