ATOMISTIC-SCALE INVESTIGATION OF THE GROWTH KINETICS OF ALUMINUM OXIDE LAYERS ON ALUMINUM NANOPARTICLES AND GERMANIUM-BASED SEMICONDUCTORS USING THE REAXFF REACTIVE FORCE FIELD

Open Access
Author:
Hong, Sung Wook
Graduate Program:
Mechanical Engineering
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
June 13, 2016
Committee Members:
  • Adri C.T. van Duin, Dissertation Advisor/Co-Advisor
  • Adri C.T. van Duin, Committee Chair/Co-Chair
  • Yuan Xuan, Committee Member
  • Richard A Yetter, Committee Member
  • Roman Engel-Herbert, Outside Member
Keywords:
  • ReaxFF
  • Molecular Dynamics Simulations
  • Aluminum oxide layer
  • Aluminum nanoparticles
  • Ge slab
Abstract:
In this dissertation, the ReaxFF potential was employed to investigate the complex surface chemistry of two nano-scale systems, including growth of aluminum oxide (Al2O3) layers on aluminum nanoparticles (ANPs) and Ge-based semiconductors. ANPs have been considered “energetic materials” due to their high enthalpy of oxidation and potentially applicable to rocket propellant formulations. In addition, there is a growing interest in using the Ge-based semiconductors to replace conventional Si-based semiconductors. However, a quantitative and comprehensive understanding of kinetic mechanisms associated with the above-mentioned systems has not yet been fully achieved, primarily due to complexities of their reaction processes in nature. Given this, the present work is motivated by two research questions: (1) What are the dominant factors that give a higher degree of energy efficiency during the oxidation process of ANPs, and (2) What is the optimal guidance for manufacturing Ge-based semiconductors? As such, this study aims to gain atomistic-scale insights into growth kinetics of passivation layers on ANPs and Ge surfaces using the ReaxFF reactive force field method. To achieve these aims, research strategies included: (a) application of the ReaxFF potential for Al/O system being chosen as a means of understanding the mechanism of the oxidation of ANPs; (b) development and application of a ReaxFF reactive force field for Al/C/H/O interactions to study the effects of surface modification on the oxidation kinetics of the ANPs; and (c) extension of the ReaxFF potential to Ge/Al/C/H/O systems to directly model an Al2O3 atomic layer deposition (ALD) process on Ge surfaces, and comparing computational results with experimental work. Our findings from combined ReaxFF and experimental studies offer very promising options and systematic strategies for the ANPs and the Ge-based semiconductors to be used in the combustion and the ALD applications, respectively. In summary, this dissertation clarifies mechanisms for growth kinetics of passivation layers (i.e., Al2O3 layer) on ANPs and Ge surfaces and suggests future directions for studying the reaction kinetics of a wide range of complex nano-scale systems from an atomistic-scale viewpoint.