Theses and Dissertations from UMD

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New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM

More information is available at Theses and Dissertations at University of Maryland Libraries.

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    MONOLAYER MOLYBDENUM DISULFIDE IN SEMICONDUCTOR ELECTRONICS
    (2023) Mazzoni, Alexander; Daniels, Kevin M; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Two-dimensional (2D) semiconductors are a new class of materials being researched due to their unique electrical, optical, and mechanical properties compared to their bulk counterparts. Here I investigate the use of the 2D semiconductor molybdenum disulfide (MoS2) as the active channel material in various electronic devices and circuits. Motivation is provided for 2D materials in general and monolayer MoS2 in particular, followed by an overview of the material properties of MoS2 and a relevant literature review. Back-gated field-effect transistors (FETs) were fabricated and characterized to investigate the impact of growth conditions on material properties, and to study the performance of different contact metals. A top-gated fabrication process was developed to make RF transistors and simple amplifier circuits on rigid and flexible substrates. Finally, device operating characteristics were modeled using simple transistor current-voltage equations, and Monte Carlo electron transport simulations were performed to demonstrate the importance of device operating temperature and intervalley separation in the conduction band.
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    Electronic Properties of Carbon Nanotubes studied in Field-Effect Transistor Geometries
    (2004-05-12) Dürkop, Tobias; Fuhrer, Michael S; Physics
    Due to their outstanding properties carbon nanotubes have attracted considerable research effort during the last decade. While they serve as an example of a 1-dimensional electron system allowing one to study fundamental quantum effects nanotubes-especially semiconducting nanotubes-are an interesting candidate for next-generation transistor application with the potential to replace silicon-based devices. I have fabricated nanotubes using chemical vapor deposition techniques with various catalysts and gas mixtures. The nanotubes produced with these techniques vary in length from 100 nm to several hundreds of micrometers. While data taken on shorter metallic and semiconducting devices show Coulomb blockade effects, the main part of this work is concerned with measurements that shed light on the intrinsic properties of semiconducting nanotubes. On devices with lengths of more than 300 um I have carried out measurements of the intrinsic hole mobility as well as the device-specific field-effect mobility. The mobility measured on these nanotube devices at room temperature exceeds that of any semiconductor known previously. Another important consideration in nanotube transistor applications are hysteresis effects. I present measurements on the time scales involved in some of these hysteresis effects and a possible application of the hysteresis for memory devices.