Open AccessFirst-Principles Studies of Nucleation of Atomic-Layered Molybdenum Disulfide by Atomic Layer Deposition
Author(s) -
Matthew Lawson
Publication year - 2021
Language(s) - English
Resource type - Dissertations/theses
DOI - 10.18122/td.1821.boisestate
Subject(s) - atomic layer deposition , nucleation , molybdenum disulfide , stoichiometry , density functional theory , atomic units , ionic bonding , limiting , molybdenum , nanotechnology , materials science , nanoscopic scale , chemistry , deposition (geology) , chemical physics , layer (electronics) , computational chemistry , inorganic chemistry , ion , metallurgy , physics , mechanical engineering , organic chemistry , quantum mechanics , engineering , paleontology , sediment , biology
This dissertation implements first-principles calculations to understand the nucleation mechanisms for atomic layer deposition (ALD) of molybdenum disulfide (MoS 2 ) using MoF 6 and H 2 S precursors. ALD is a self-limiting process that can deposit a range of materials at the nanoscale, while maintaining chemical stoichiometry, atomic scale thickness control, and can conform to high-aspect ratio substrate designs. ALD is extremely sensitive to surface chemistry and morphology; therefore, it is critical to understand how these factors control deposition. Density functional theory (DFT) was used to understand what factors can control the nucleation for ALD of MoS 2 using MoF 6 and H 2 S. Surface hydroxyls on oxide substrates help facilitate the formation of ionic MF x (M = metal, x = 1, 2, 3) species, which thermodynamically drive the first-half cycle of ALD. DFT calculations were supported by experimental measurements to validate computational predictions. DFT and experiment both confirmed that there are different types of nucleation mechanisms during ALD of MoS 2 . The types of mechanisms depend on which precursor is introduced, and highlights the complexities during nucleation of MoS 2 during ALD.