Date of Graduation

12-2024

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Materials Science & Engineering (PhD)

Degree Level

Graduate

Department

Materials Science & Engineering

Advisor/Mentor

Manasreh, Bothina H.

Committee Member

Manasreh, Omar O.

Second Committee Member

Gea-Banacloche, Julio R.

Third Committee Member

Dix, Jeff

Fourth Committee Member

Ware, Morgan E.

Keywords

2D materials; transition metal dichalcogenides; rhenium disulfide; Density Functional Theory; chemical vapor deposition; optoelectronics

Abstract

Two-dimensional (2D) transition metal dichalcogenides (TMDs) have garnered considerable interest for their potential in optoelectronics and photonics owing to their remarkable combination of electronic, optical, and mechanical properties. These characteristics distinguish them from other 2D materials, including graphene, making them particularly valuable for next-generation technologies. This dissertation focuses on ReS₂, a 2D TMD with a unique anisotropic 1T distorted crystal structure. The research aims to elucidate its fundamental properties through a combination of theoretical modeling, material synthesis, and experimental characterization techniques, with the goal of optimizing ReS₂ for device applications. A theoretical investigation utilizing Density Functional Theory (DFT) calculations was conducted to examine the electronic band structure, optical properties, and vibrational modes of Rhenium Disulfide (ReS₂). Specifically, the calculations predicted a bandgap of 1.35 eV and 1.43 eV for bulk and monolayer ReS₂ respectively. Furthermore, the phonon dispersion at the Γ point was identified within the range of 130 cm⁻¹ to approximately 430 cm⁻¹.

In parallel with the theoretical investigation, high-quality ReS₂ flakes were synthesized using chemical vapor deposition (CVD) on silica and SiO₂/Si. The synthesized ReS₂ samples were experimentally characterized using a range of spectroscopic and microscopic techniques. The structural integrity of the grown samples was validated through X-ray diffraction (XRD), while Scanning Electron Microscopy coupled with Energy Dispersive X-ray Spectroscopy (SEM-EDS) was employed to analyze the elemental composition. Photoluminescence spectra showed excitonic features associated with interband transitions in both monolayer flakes and bulk-like structures. The DFT calculations and experimental measurements of Raman scattering spectrum were comparable. The optical absorbance spectrum of ReS₂ flakes grown on a silica substrate exhibited excitonic features at room temperature.

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