TY - JOUR
T1 - Resolving the Heat of Trimethylaluminum and Water Atomic Layer Deposition Half-Reactions
AU - Bielinski, Ashley R.
AU - Kamphaus, Ethan P.
AU - Cheng, Lei
AU - Martinson, Alex B.F.
N1 - Publisher Copyright:
© 2022 UChicago Argonne, LLC, Operator of Argonne National Laboratory. Published by American Chemical Society.
PY - 2022/8/24
Y1 - 2022/8/24
N2 - Atomic layer deposition (ALD) is a surface synthesis technique that is characterized by self-limiting reactions between gas-phase precursors and a solid substrate. Although ALD processes have been demonstrated that span the periodic table, a greater understanding of the surface chemistry that affords ALD is necessary to enable greater precision, including area- and site-selective growth. We offer new insight into the thermodynamics and kinetics of the trimethylaluminum (TMA) and H2O ALD half-reactions with calibrated and time-resolved in situ pyroelectric calorimetry. The half-reactions produce 3.46 and 2.76 eV/Al heat, respectively, which is greater than the heat predicted by computational models based on crystalline Al2O3 substrates and closely aligned with the heat predicted by standard heats of formation. The pyroelectric thin-film calorimeter offers submillisecond temporal resolution that uniquely and clearly resolves precursor delivery and reaction kinetics. Both half-reactions are observed to exhibit multiple kinetic rates, with average TMA half-reaction rates at least 2 orders of magnitude faster than the H2O half-reaction kinetics. Comparing the experimental heat with published computational literature and additional first-principles modeling highlights the need to refine our models and mechanistic understanding of even the most ubiquitous ALD reactions.
AB - Atomic layer deposition (ALD) is a surface synthesis technique that is characterized by self-limiting reactions between gas-phase precursors and a solid substrate. Although ALD processes have been demonstrated that span the periodic table, a greater understanding of the surface chemistry that affords ALD is necessary to enable greater precision, including area- and site-selective growth. We offer new insight into the thermodynamics and kinetics of the trimethylaluminum (TMA) and H2O ALD half-reactions with calibrated and time-resolved in situ pyroelectric calorimetry. The half-reactions produce 3.46 and 2.76 eV/Al heat, respectively, which is greater than the heat predicted by computational models based on crystalline Al2O3 substrates and closely aligned with the heat predicted by standard heats of formation. The pyroelectric thin-film calorimeter offers submillisecond temporal resolution that uniquely and clearly resolves precursor delivery and reaction kinetics. Both half-reactions are observed to exhibit multiple kinetic rates, with average TMA half-reaction rates at least 2 orders of magnitude faster than the H2O half-reaction kinetics. Comparing the experimental heat with published computational literature and additional first-principles modeling highlights the need to refine our models and mechanistic understanding of even the most ubiquitous ALD reactions.
UR - http://www.scopus.com/inward/record.url?scp=85136297719&partnerID=8YFLogxK
U2 - 10.1021/jacs.2c05460
DO - 10.1021/jacs.2c05460
M3 - Article
C2 - 35943821
AN - SCOPUS:85136297719
SN - 0002-7863
VL - 144
SP - 15203
EP - 15210
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
IS - 33
ER -