Dr. Jeffrey Elam
Wednesday, April 7, 2021
"Elucidating the Mechanisms for Atomic Layer Growth through In Situ Studies"
ABSTRACT: Atomic Layer Deposition (ALD) provides exquisite control over film thickness and
composition and yields excellent conformality over large areas and within nanostructures. These desirable
attributes derive from self-limiting surface chemistry, and can disappear if the self-limitation is removed.
Understanding the surface chemical reactions, i.e. the ALD mechanism, can provide insight into the limits of
self-limitation allowing better control, successful scale up, and the invention of new processes. In situ
measurements are very effective for elucidating ALD growth mechanisms. In this presentation, I will describe
investigations into the growth mechanisms of ALD nanocomposite films comprised of conducting (e.g. W, Mo
and Re) and insulating (e.g. Al2O3, ZrO2 and TiO2) components using in situ measurements. These ALD
nanocomposites have applications in particle detection, energy storage, and solar power. We have performed
extensive in situ studies using quartz crystal microbalance (QCM), quadrupole mass spectrometry (QMS),
Fourier transform infrared (FTIR) absorption spectroscopy, and current-voltage measurements. These
measurements reveal unusual ALD chemistry occurring upon transitioning between the ALD processes for the
two components. This results in unique reaction products that affect the properties of the films in beneficial
ways. The knowledge gained from our in situ studies of the ALD nanocomposite films has helped us to
overcome problems encountered when we scaled up the ALD processes to large area substrates. Beyond
fundamental understanding, in situ measurements are extremely effective in ALD process development and
process monitoring. I will end my talk by describing our recent work combining in situ measurements and
machine learning to accelerate ALD process development.