In Situ Pyroelectric Heat Detection for Elucidating Atomic Layer Deposition Thermodynamics and Kinetics

The detailed mechanisms, kinetics, thermodynamics, and complexities of even the most well-studied atomic layer deposition (ALD) reactions remain insufficiently resolved experimentally to test present computational hypotheses. We design, implement, calibrate, and electrically model a pyroelectric thin film calorimeter to enable quantitative ALD reaction heat detection. With a thermal and temporal resolution down to 0.1 μJ/cm² and 50 ns, this sensitive and ultrafast probe is poised to improve our fundamental understanding of numerous ALD reaction mechanisms through quantitative comparison to first-principles computation predictions. We offer new insight into the thermodynamics and kinetics of the trimethylaluminum (TMA) and H₂O ALD half reactions. The half-reactions produce heat greater than that predicted by computational models based on crystalline Al₂O₃ substrates and closely aligned with the heat predicted by standard heats of formation. 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.