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Full-Text Articles in Physical Sciences and Mathematics
Exploring The Electrical Properties Of Twisted Bilayer Graphene, William Shannon
Exploring The Electrical Properties Of Twisted Bilayer Graphene, William Shannon
Senior Theses
Two-dimensional materials exhibit properties unlike anything else seen in conventional substances. Electrons in these materials are confined to move only in the plane. In order to explore the effects of these materials, we have built apparatus and refined procedures with which to create two-dimensional structures. Two-dimensional devices have been made using exfoliated graphene and placed on gold contacts. Their topography has been observed using Atomic Force Microscopy (AFM) confirming samples with monolayer, bilayer, and twisted bilayer structure. Relative work functions of each have been measured using Kelvin Probe Force Microscopy (KPFM) showing that twisted bilayer graphene has a surface potential …
Measuring The Double Layer Capacitance Of Electrolyte Solutions Using A Graphene Field Effect Transistor, Agatha Ulibarri
Measuring The Double Layer Capacitance Of Electrolyte Solutions Using A Graphene Field Effect Transistor, Agatha Ulibarri
Senior Theses
When operating graphene field effect transistors (GFETs) in fluid, a double layer capacitance (Cdl) is formed at the surface. In the literature, the Cdl is estimated using values obtained using metal electrode experiments. Due to the distinctive electronic and surface properties of graphene, there is reason to believe these estimates are inadequate. This work seeks to directly characterize the double layer capacitance of a GFET. A unique method for determining the Cdl has been implemented, and data has been obtained for three electrolytes and one ionic fluid. The results yield dramatically lower Cdl values than …
Modeling The Behavior Of The Graphene To Liquid Interfaces In An Electrolytic Liquid, Caitlin Duffner
Modeling The Behavior Of The Graphene To Liquid Interfaces In An Electrolytic Liquid, Caitlin Duffner
Senior Theses
Understanding the mechanism for charge transfer between a graphene biosensor and its electrodes within an electrolyte solution is vital to better understand the sources of electrical noise in the system. By measuring the effective resistance and capacitance of the system at different frequencies, it is possible to develop a circuit model of the system's electrical behavior. This model provides a deeper understanding of the fundamental interactions that occur in a top-gated graphene device and provides opportunities to improve a signal. To reduce noise created at the liquid to graphene interface, a buffer layer of Yttrium Oxide was applied. While the …
Effect Of Electrolyte Concentration On The Capacitance And Mobility Of Graphene, Flint A. Martino
Effect Of Electrolyte Concentration On The Capacitance And Mobility Of Graphene, Flint A. Martino
Senior Theses
The use of graphene field-effect transistors as a biosensor is increasingly being used to study biological phenomena, due to the sensitivity and low reactivity of graphene. To further improve sensitivity in biological environments, we examined how different salt concentrations affect the mobility of capacitance of the graphene. Samples were also measured after an annealing process. We report on the positive correlation between sensitivity and electrolyte concentration and speculate on methods to improve future detectors. Mobility of the device was found to change from 1.07*103cm2/ (V*s) in de-ionized water to 2.78*103cm2/ (V*s) in …
Measuring Charge Carrier Mobility In Graphene, Christina A. Harmon
Measuring Charge Carrier Mobility In Graphene, Christina A. Harmon
Senior Theses
This research reports measurements of electron mobility in Graphene Field Effect Transistors (GFET), gated with liquid. Mobility is a quantity describing how easily charge carriers move through a material. GFET biosensors have the greatest sensitivity when the mobility is high; therefore, increasing mobility should improve sensitivity of these and similar devices. An optimal method was established for preparing samples and taking measurements of a liquid-gate device. Sheet conductivity was measured using van der Pauw geometry and carrier density was determined from measurements of the liquid-gate capacitance. It is shown that mobility improves after the graphene surface is cleaned by an …
Optimization Of Chemical Vapor Deposition Grown Graphene, Andrew Tan
Optimization Of Chemical Vapor Deposition Grown Graphene, Andrew Tan
Senior Theses
Graphene can be used as the active film in a gas sensor. To provide the best possible electrical properties, it is important that graphene films be single-layered and single-crystalline. A low vacuum chemical vapor deposition (CVD) chamber was constructed to grow graphene with these properties. The effect of growth parameters, such as annealing times and methane partial pressure, on the quality of graphene was investigated. Raman spectra of graphene were used to quantify the characteristics of the synthesized graphene. Graphene synthesized through CVD has two major peaks, the G (~1570cm-1) and the 2D peak (~2700 cm-1). …