Kusaba, AkiraLi, Guanchenvon Spakovsky, Michael R.Kangawa, YoshihiroKakimoto, Koichi2017-09-202017-09-202017-08-15Kusaba, A.; Li, G.; von Spakovsky, M.R.; Kangawa, Y.; Kakimoto, K. Modeling the Non-Equilibrium Process of the Chemical Adsorption of Ammonia on GaN(0001) Reconstructed Surfaces Based on Steepest-Entropy-Ascent Quantum Thermodynamics. Materials 2017, 10, 948.http://hdl.handle.net/10919/79351Clearly understanding elementary growth processes that depend on surface reconstruction is essential to controlling vapor-phase epitaxy more precisely. In this study, ammonia chemical adsorption on GaN(0001) reconstructed surfaces under metalorganic vapor phase epitaxy (MOVPE) conditions (3Ga-H and N_ad-H + Ga-H on a 2 × 2 unit cell) is investigated using steepest-entropy-ascent quantum thermodynamics (SEAQT). SEAQT is a thermodynamic-ensemble based, first-principles framework that can predict the behavior of non-equilibrium processes, even those far from equilibrium where the state evolution is a combination of reversible and irreversible dynamics. SEAQT is an ideal choice to handle this problem on a first-principles basis since the chemical adsorption process starts from a highly non-equilibrium state. A result of the analysis shows that the probability of adsorption on 3Ga-H is significantly higher than that on N_ad-H + Ga-H. Additionally, the growth temperature dependence of these adsorption probabilities and the temperature increase due to the heat of reaction is determined. The non-equilibrium thermodynamic modeling applied can lead to better control of the MOVPE process through the selection of preferable reconstructed surfaces. The modeling also demonstrates the efficacy of DFT-SEAQT coupling for determining detailed non-equilibrium process characteristics with a much smaller computational burden than would be entailed with mechanics-based, microscopic-mesoscopic approaches.application/pdfenCreative Commons Attribution 4.0 Internationalmetalorganic vapor phase epitaxygallium nitridechemical adsorptionsurface reconstructiondensity functional theory calculationssteepest-entropy-ascent quantum thermodynamicsArticle - Refereed2017-09-20https://doi.org/10.3390/ma10080948