Publication Date

5-2021

Date of Final Oral Examination (Defense)

3-25-2021

Type of Culminating Activity

Dissertation

Degree Title

Doctor of Philosophy in Materials Science and Engineering

Department

Materials Science and Engineering

Major Advisor

Lan Li, Ph.D.

Major Advisor

Elton Graugnard, Ph.D.

Advisor

Dave Estrada, Ph.D.

Advisor

Winnie Wong-Ng, Ph.D.

Abstract

This dissertation implements first-principles calculations to understand the nucleation mechanisms for atomic layer deposition (ALD) of molybdenum disulfide (MoS2) using MoF6 and H2S 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 MoS2 using MoF6 and H2S. Surface hydroxyls on oxide substrates help facilitate the formation of ionic MFx (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 MoS2. The types of mechanisms depend on which precursor is introduced, and highlights the complexities during nucleation of MoS2 during ALD.

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