Date of Graduation

12-2024

Document Type

Thesis

Degree Name

Master of Science in Materials Engineering (MS)

Degree Level

Graduate

Department

Materials Science & Engineering

Advisor/Mentor

Wejinya, Uche C.

Committee Member

Churchill, Hugh O.H.

Second Committee Member

Meng, Henry

Third Committee Member

Ware, Morgan E.

Keywords

Field-Effect Transistors; Functionalization; Graphene; Hydrogen; Non-Covalent; Sensing

Abstract

The hydrogen economy is rapidly advancing and is poised to become one of the world's largest economies, driven by the abundance of hydrogen gas. Several organizations, particularly in the United States of America, are closely or have been monitoring this development, with rapidly increasing interest. Considering that hydrogen gas has no taste, smell (odor), or color, and very combustible, it’s imperative to develop detectors and sensors capable of rapidly detecting leaks to prevent application disasters. Owing to its extraordinary mechanical and electrical characteristics, graphene is the material that has been studied the most. When combined with hexagonal boron nitride (hBN), an excellent insulator with an atomically flat surface, graphene is being studied as a platform for hydrogen sensing applications to enhance response time in detecting hydrogen. Since graphene is inert and hydrophobic, non-covalent reagents such as sodium octyl sulfate (SOS) and sodium cholate (SC) reduce its hydrophobicity, thereby increasing the surface's affinity for hydrogen gas molecules. A higher concentration (1% wt/vol) of SOS and an extended treatment time of 2 hours resulted in the delamination of the graphene. Therefore, lower concentrations of the SOS surfactant and shorter treatment times of 2 and 4 minutes prevented the graphene from delaminating, making these conditions suitable for use in this project. It was observed that the roughness of the CVD graphene increased following functionalization. This increase may hinder electronic transport measurements, particularly affecting mobility. Graphene and hBN heterostructure devices were functionalized with 0.125% wt/vol and 0.25% wt/vol solutions for 4 minutes, after which their mobilities were measured. Lower concentrations of 0.125% wt/vol improved the mobility of the devices after functionalization, whereas 0.25% wt/vol led to a decrease in post-functionalization mobility. Considering the primary objective of this project, which focuses on sensing applications, a concentration of 0.125% wt/vol is most suitable.

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