Date of Graduation

8-2022

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Materials Science & Engineering (PhD)

Degree Level

Graduate

Department

Materials Science & Engineering

Advisor/Mentor

Wejinya, Uche C.

Committee Member

Tian, Z. Ryan

Second Committee Member

Millett, Paul C.

Third Committee Member

Meng, Xiangbo

Fourth Committee Member

Leftwich, Matthew B.

Keywords

Hydrogen sensors; Graphene; Chemical vapor deposition

Abstract

With graphene at the center of several application areas such as sensing, circuits, high-frequency devices for communication systems, etc., it is crucial to understand how the intrinsic properties of devices made from graphene and other materials like platinum and palladium nanoparticles affect the performance of such devices for the specific application area. Many graphene-based devices for different application areas have focused mainly on the material composition of the graphene-based devices and how it affects performance parameters for the specific application. However, it would be insightful to understand how the intrinsic electrical properties of the graphene devices for different applications affect the performance parameter for those application areas.Following the path to be able to correlate the intrinsic electrical properties of graphene-based devices, the first part of this dissertation explored the electrical transport properties of graphene on novel locally-sourced insulating substrate Cadmium trithiophosphate (IV)- CdPS3. Employing the fabrication techniques for 2-Dimensional (2D) materials such as mechanical exfoliation, electron beam lithography, metal evaporation, atomic force microscopy, and low-temperature transport measurement using an optical cryostat, graphene devices on CdPS3, and graphene devices on hexagonal boron nitride (hBN) were fabricated and characterized. CdPS3 was discovered to have a flatter surface than hBN, and graphene devices on CdPS3 appear to generate a highly conductive interface between the graphene and CdPS3. The second part of this work explored the non-covalent functionalization of commercially available CVD graphene Si/SiO2 substrate using Sodium Dodecyl Sulphate (SDS). Functionalization of graphene is vital for the integration of graphene in different applications. Functionalization helps to overcome the hydrophobic and inert nature of graphene for further processing such as atomic layer deposition. CVD graphene samples were treated with different surfactant concentrations and for different treatment times. Characterization of the CVD graphene samples was done using atomic force microscopy and optical microscopy. The CVD graphene was observed to delaminate from the substrate and the extent it delaminated from the substrate depended on the surfactant concentration and treatment duration. To achieve a higher concentration of surfactant for CVD graphene functionalization, the surfactant was dissolved in water and isopropyl alcohol. This approach prevented the delamination of the graphene from the substrate and different concentrations of surfactants and duration of treatment affect the surface roughness of the functionalized graphene.

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