Modeling the non-equilibrium process of the chemical adsorption of ammonia on GaN(0001) reconstructed surfaces based on steepest-entropy-ascent quantum thermodynamics

Kusaba, A., Li, G. , von Spakovsky, M. R., Kangawa, Y. and Kakimoto, K. (2017) Modeling the non-equilibrium process of the chemical adsorption of ammonia on GaN(0001) reconstructed surfaces based on steepest-entropy-ascent quantum thermodynamics. Materials, 10(12), 948. (doi: 10.3390/ma10080948)

Abstract

Clearly 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 Nad-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 Nad-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.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Li, Dr Guanchen
• Authors: Kusaba, A., Li, G., von Spakovsky, M. R., Kangawa, Y., and Kakimoto, K.
• College/School: College of Science and Engineering > School of Engineering > Systems Power and Energy
• Journal Name: Materials
• Publisher: MDPI
• ISSN: 1996-1944
• ISSN (Online): 1996-1944
• Published Online: 15 August 2017
• Copyright Holders: Copyright © 2017 The Authors
• First Published: First published in Materials 10(8): 948
• Publisher Policy: Reproduced under a Creative Commons License