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INTERFACIAL BEHAVIOR IN POLYMER DERIVED CERAMICS AND SALT WATER PURIFICATION VIA 2D MOS2
Title
INTERFACIAL BEHAVIOR IN POLYMER DERIVED CERAMICS AND SALT WATER PURIFICATION VIA 2D MOS2.
Creator
Li, Hao, An, Linan, Jung, YeonWoong, Zhai, Lei, Feng, Xiaofeng, Yu, Xiaoming, University of Central Florida
Abstract / Description
In the present dissertation, the behavior of the internal potential barrier in a polymer-derived amorphous SiAlCN ceramic was studied by measuring its complex impedance spectra at various dc bias as well as different testing and annealing temperatures. The complex impedancespectra of the polymer-derived a-SiAlCN were measured under various dc bias voltages in a temperature range between 50 and 150?(&)deg;C, as well as different annealing temperatures (1100-1400 (&)deg;C). All spectra,...
Show moreIn the present dissertation, the behavior of the internal potential barrier in a polymer-derived amorphous SiAlCN ceramic was studied by measuring its complex impedance spectra at various dc bias as well as different testing and annealing temperatures. The complex impedancespectra of the polymer-derived a-SiAlCN were measured under various dc bias voltages in a temperature range between 50 and 150?(&)deg;C, as well as different annealing temperatures (1100-1400 (&)deg;C). All spectra, regardless of temperature and bias, consist of two semi-circular arcs,corresponding to the free-carbon phase and the interface, respectively. The impedance of the free-carbon phase is independent of the bias, while that of the interface decreased significantly with increasing dc bias. It is shown that the change of the interfacial capacitance with the bias can be explained using the double Schottky barrier model. The charge-carrier concentration and potential barrier height were estimated by comparing the experimental data and the model.The results revealed that increasing testing temperature led to an increased charge-carrier concentration and a reduced barrier height, both following Arrhenius dependence, whereas the increase in annealing temperature resulted in increased charge-carrier concentration and barrier height. The phenomena were explained in terms of the unique bi-phasic microstructures of the material. The research findings reveal valuable microstructural information of temperaturedependent properties of polymer derived ceramics, and should contribute towards more precise understanding and control of the electrical as well as dielectric properties of polymer derivedceramics. Furthermore, the desalination performances and underlying mechanisms of two-dimensional CVD-grown MoS2 layers membranes have been experimentally assessed. Based on a successful large-area few-layer 2D materials growth, transfer and integration method, the 2D MoS2 layers membranes showed preserved chemical and microstructural integrity after integration. The few-layer 2D MoS2 layers demonstrated superior desalination capability towards various types of seawater salt solutions approaching theoretically-predicted values. Such performances are attributed to the dimensional and geometrical effect, as well as the electrostatic interaction of the inherently-present CVD-induced atomic vacancies for governingboth water permeation and ionic sieving at the solution/2D-layer interfaces.
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Date Issued
2019
Identifier
CFE0007830, ucf:52813
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0007830
Chemical Vapor Deposition Growth of Large Area 2D MoS2 Layers: Layer Orientation Control, Heterostructure Integration, And Applications for Stretchable Sensors.
Title
Chemical Vapor Deposition Growth of Large Area 2D MoS2 Layers: Layer Orientation Control, Heterostructure Integration, And Applications for Stretchable Sensors.
Creator
Islam, Md. Ashraful, Jung, YeonWoong, Sundaram, Kalpathy, Yuan, Jiann-Shiun, Roy, Tania, Cho, Hyoung Jin, University of Central Florida
Abstract / Description
Two-dimensional (2D)-layered MoS2 layers have exhibited a broad set of unusual and superior material properties unattainable in any traditional bulk materials, drawing significant research interests nowadays. For instance, they present excellent semiconducting properties accompanying high carrier mobility and large current ON/OFF ratio as well as extensive in-plane strain limit and thickness, projecting high suitably for emerging flexible and stretchable electronics. Such properties and...
Show moreTwo-dimensional (2D)-layered MoS2 layers have exhibited a broad set of unusual and superior material properties unattainable in any traditional bulk materials, drawing significant research interests nowadays. For instance, they present excellent semiconducting properties accompanying high carrier mobility and large current ON/OFF ratio as well as extensive in-plane strain limit and thickness, projecting high suitably for emerging flexible and stretchable electronics. Such properties and applications strongly depend on the physical orientation and chemical composition of constituent 2D layers. 2D MoS2 layers chemically grown in two distinct orientations, e.g., horizontal alignment for electronics and optoelectronics, and vertical alignment for electrochemical and sensing applications. Moreover, 2D heterostructure layers composed of vertically stacked dissimilar 2D TMDs held via weak van der Waals (vdW) attractions offer unique 2D/2D interfaces, envisioned to display exotic material properties, unattainable in their monocomponent counterparts. However, the underlying principle of their layer orientation-controlled growth and integrations are not well suited for scalable production, leaving their projected technological opportunities far from being realized for various novel applications. Herein, I study various aspects of 2D MoS2 layers that were studied from their large-area layer-orientation controlled growth and heterostructures integration to applications in stretchable electronic devices. I developed a chemical vapor deposition (CVD) synthesis, which can grow large-area ((>) cm2) 2D MoS2 layers in a layer-controlled manner and investigated their underlying growth mechanism. I then developed a viable transfer approach of the as-grown 2D layers and integrated them into secondary target substrates to realize a new type of 2D MoS2-layers based heterostructures. To further extend their layer-controlled CVD growth and integration approach, a high-performance stretchable 2D MoS2-based electrical sensors were demonstrated on the elastomeric substrates with unconventional structural layouts. This study paves the way to explore this emerging atomically-thin material in realizing a wide range of unusual device and technologies which have been foreseen to be impossible otherwise.
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Date Issued
2019
Identifier
CFE0007820, ucf:52812
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0007820