  Atomic layer deposition (ALD) provides uniform and conformal thin films that
are of interest for a range of applications. To better understand the
properties of amorphous ALD films, we need improved understanding of their
local atomic structure. Previous work demonstrated measurement of how the local
atomic structure of ALD-grown aluminum oxide (AlOx) evolves in operando during
growth by employing synchrotron high energy X-ray diffraction (HE-XRD). In this
work, we report on efforts to employ electron diffraction pair distribution
function (ePDF) measurements using more broadly available transmission electron
microscope (TEM) instrumentation to study the atomic structure of amorphous
ALD-AlOx. We observe electron beam damage in the ALD-coated samples during ePDF
at ambient temperature and successfully mitigate this beam damage using ePDF at
cryogenic temperatures (cryo-ePDF). We employ cryo-ePDF and Reverse Monte Carlo
(RMC) modeling to obtain structural models of ALD-AlOx coatings formed at a
range of deposition temperatures from 150-332{\deg}C. From these model
structures, we derive structural metrics including stoichiometry, pair
distances, and coordination environments in the ALD-AlOx films as a function of
deposition temperature. The structural variations we observe with growth
temperature are consistent with temperature-dependent changes in the surface
hydroxyl density on the growth surface. The sample preparation and cryo-ePDF
procedures we report here can be used for routine measurement of ALD-grown
amorphous thin films to improve our understanding of the atomic structure of
these materials, establish structure-property relationships, and help
accelerate the timescale for the application of ALD to address technological
needs.
