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You searched for +publisher:"Catholic U of America" +contributor:("Pegg, Ian L."). Showing records 1 – 2 of 2 total matches.

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1. Henderson, Mark. Polaronic Transport in Phosphate Glasses Containing Transition Metal Ions.

Degree: PhD, Physics, 2015, Catholic U of America

The goal of this dissertation is to characterize the basic transport properties of phosphate glassescontaining various amounts of TIs and to identify and explain any electronic phase transitionswhich may occur. The P2O5-V2O5-WO3 (PVW) glass system will be analyzed to find the effectof TI concentration on conduction. In addition, the effect of the relative concentrations ofnetwork forming ions (SiO2 and P2O5) on transport will be studied in the P2O5-SiO2-Fe2O3 (PSF)system. Also presented is a numerical study on a tight-binding model adapted for the purposes ofmodelling Gaussian traps, mimicking TI’s, which are arranged in an extended network. Theresults of this project will contribute to the development of fundamental theories on theelectronic transport in glasses containing mixtures of transition oxides as well as thosecontaining multiple network formers without discernible phase separation.The present study on the PVW follows up on previous investigation into the effect on mixedtransition ions in oxide glasses. Past research has focused on glasses containing transition metalions from the 3d row. The inclusion of tungsten, a 5d transition metal, adds a layer of complexitythrough the mismatch of the energies of the orbitals contributing to localized states. The datahave indicated that a transition reminiscent of a metal-insulator transition (MIT) occurs in thissystem as the concentration of tungsten increases. As opposed to some other MIT-like transitionsfound in phosphate glass systems, there seems to be no polaron to bipolaron conversion. Instead,the individual localization parameter for tungsten noticeably decreases dramatically at thetransition point as well as the adiabaticity.Another distinctive feature of this project is the study of the PSF system, which contains two truenetwork formers, phosphorous pentoxide (P2O5) and silicon dioxide (SiO2). It is not usuallypossible to do a reliable investigation of the conduction properties of such glasses because thetwo network formers will tend to separate into different phases, making it difficult to obtainhomogenous samples. The PSF system proved easier to study than other systems. The hopping inthis system seems to be dominated by the Greaves mid-range mechanism. In addition, in samplescontaining the same proportion of iron, conductivities were found to not depend noticeably oncomposition, supporting the use of models focusing on the transition metal ions in calculatingconductivity. Despite ostensibly changing the structural and metrical properties of the network,the ratio of the concentration of the network formers only appears to have an effect on theconductivity through changing the inter-atomic distance of iron.The numerical model adds to the evidence for the dominating contribution on the nearestneighborordering of TI ions on the electrical properties of a glass; especially interesting is… Advisors/Committee Members: Dutta, Biprodas (Advisor), Pegg, Ian L. (Other), Philip, John (Other).

Subjects/Keywords: Physics; Condensed matter physics; glass; polarons; quantum mechanics; semiconductors; solid state

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APA (6th Edition):

Henderson, M. (2015). Polaronic Transport in Phosphate Glasses Containing Transition Metal Ions. (Doctoral Dissertation). Catholic U of America. Retrieved from http://hdl.handle.net/1961/cuislandora:28302

Chicago Manual of Style (16th Edition):

Henderson, Mark. “Polaronic Transport in Phosphate Glasses Containing Transition Metal Ions.” 2015. Doctoral Dissertation, Catholic U of America. Accessed June 25, 2019. http://hdl.handle.net/1961/cuislandora:28302.

MLA Handbook (7th Edition):

Henderson, Mark. “Polaronic Transport in Phosphate Glasses Containing Transition Metal Ions.” 2015. Web. 25 Jun 2019.

Vancouver:

Henderson M. Polaronic Transport in Phosphate Glasses Containing Transition Metal Ions. [Internet] [Doctoral dissertation]. Catholic U of America; 2015. [cited 2019 Jun 25]. Available from: http://hdl.handle.net/1961/cuislandora:28302.

Council of Science Editors:

Henderson M. Polaronic Transport in Phosphate Glasses Containing Transition Metal Ions. [Doctoral Dissertation]. Catholic U of America; 2015. Available from: http://hdl.handle.net/1961/cuislandora:28302

2. Sapkota, Keshab Raj. Spin Dependent Transport Properties of Metallic and Semiconducting Nanostructures.

Degree: PhD, Physics, 2015, Catholic U of America

Present day computing and communication devices rely on two different classes of technologies; information processing devices are based on electrical charge transport while information storage devices are based on orientation of electron spins in magnetic materials. Realization of a hybrid-type device based on charge as well as spin properties of electrons would perform both of these actions thereby enhancing computation power to many folds and reducing power consumptions. This dissertation focuses on the fabrication of such spin-devices based on metallic and semiconducting nanostructures. A simplified design of the spin-device consists of a spin injector, a semiconducting or a metallic channel, and a spin detector. The channel is the carrier of spin signal from the injector to the detector, and therefore plays a crucial role in the manipulation of spin properties in the device. In this work, nanostructures such as nanowires and nanostripes were used to function as the channel in the spin-device. Various physical and chemical methods were used to synthesize the nanostructures. Fabrication of the spin-devices from the nanostructures were carried out using two-stage electron beam lithography process. These spin-devices show large spin relaxation lengths compared to common materials such as copper and offer potential for novel future technologies. Further, nanowires of Co2FeAl and Cd1-xMnxTe were synthesized and studied their structural, magnetic and electrical transport properties to understand whether they can be used in spin-devices as spin injectors and spin detectors. In summary, the studies carried out in this thesis opens up several new material systems for future device applications.

Degree awarded: Ph.D. Physics. The Catholic University of America

Advisors/Committee Members: Philip, John (Advisor), Pegg, Ian L. (Other), Resca, Lorenzo (Other), Bhutani, Kiran (Other), Howard, Barbara (Other).

Subjects/Keywords: Nanotechnology; Materials Science; Physics; Nanowire; Spintronics; Spin valve

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Sapkota, K. R. (2015). Spin Dependent Transport Properties of Metallic and Semiconducting Nanostructures. (Doctoral Dissertation). Catholic U of America. Retrieved from http://hdl.handle.net/1961/cuislandora:28284

Chicago Manual of Style (16th Edition):

Sapkota, Keshab Raj. “Spin Dependent Transport Properties of Metallic and Semiconducting Nanostructures.” 2015. Doctoral Dissertation, Catholic U of America. Accessed June 25, 2019. http://hdl.handle.net/1961/cuislandora:28284.

MLA Handbook (7th Edition):

Sapkota, Keshab Raj. “Spin Dependent Transport Properties of Metallic and Semiconducting Nanostructures.” 2015. Web. 25 Jun 2019.

Vancouver:

Sapkota KR. Spin Dependent Transport Properties of Metallic and Semiconducting Nanostructures. [Internet] [Doctoral dissertation]. Catholic U of America; 2015. [cited 2019 Jun 25]. Available from: http://hdl.handle.net/1961/cuislandora:28284.

Council of Science Editors:

Sapkota KR. Spin Dependent Transport Properties of Metallic and Semiconducting Nanostructures. [Doctoral Dissertation]. Catholic U of America; 2015. Available from: http://hdl.handle.net/1961/cuislandora:28284

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