Physical Sciences and Mathematics Commons^™

Tunable Electronic And Optical Properties Of Low-Dimensional Materials, Shiyuan Gao

Arts & Sciences Electronic Theses and Dissertations

Two-dimensional (2D) materials with single or a few atomic layers, such as graphene, hexagonal boron nitride (h-BN) and transition metal dichalcogenides (TMDCs), and the heterostructures or one-dimensional (1D) nanostructures they form, have attracted much attention recently as unique platforms for studying many condensed-matter phenomena and holds great potentials for nanoelectronics and optoelectronic applications. Apart from their unique intrinsic properties which has been intensively studied for over a decade by now, they also allow external control of many degrees of freedom, such as electrical gating, doping and layer stacking. In this thesis, I present a theoretical study of the electronic and …

Impact Of Chemical Doping On The Thermoelectric Charge Transport Of Organic Semiconductors, Connor J. Boyle

Doctoral Dissertations

The thermoelectric properties of organic semiconductors allow them to directly convert heat into electricity without the use of moving parts and to directly convert electricity into heat without the use of working fluids. These properties offer opportunities for the generation of electricity from non-conventional or renewable sources of heat and for refrigeration without the risk of leaking harmful working fluids at any length scale down to the nanoscale. Since organic materials are lightweight, flexible, and made from abundant resources, these opportunities could one day become affordable for widespread use and could be expanded to include specialized and otherwise difficult to …

Plasma Based Synthesis And Surface Modification Of Graphene., Rong Zhao

Electronic Theses and Dissertations

Graphene, an atom thick layer of carbon, has attracted intense scientific interest due to its exceptional electrical, mechanical and chemical properties. Especially, it provides a perfect platform to explore the unique electronic properties in absolute two-dimension. Pristine graphene possesses zero band gap and weakens its competitiveness in the field of semiconductors. In order to induce a band gap and control its semiconducting properties, functionalization and doping are two of the most feasible methods. In the context of functionalization, large area monolayer graphene synthesized by chemical vapor deposition was subjected to controlled and sequential fluorination using radio frequency plasma while monitoring …

The Effect Of Processing Conditions On The Energetic Diagram Of Cdte Thin Films Studied By Photoluminescence, Shamara P. Collins

USF Tampa Graduate Theses and Dissertations

The photovoltaic properties of CdTe-based thin films depend on recombination levels formed in the CdTe layer and at the heterojunction. The localized states are resultant of structural defects (metal sublattice, chalcogen sublattice, interstitial), controlled doping, deposition process, and/or post-deposition annealing. The photoluminescence study of CdTe thin films, from both the bulk and heterojunction, can reveal radiative states due to different defects or impurities. Identification of defects allows for potential explanation of their roles and influence on solar cell performance. A thorough understanding of the material properties responsible for solar cell performance is critical in further advancing the efficiency of devices. …

In Situ Extrinsic Doping Of Cdte Thin Films For Photovoltaic Applications, Imran Suhrid Khan

USF Tampa Graduate Theses and Dissertations

The Cadmium Telluride thin film solar cell is one of the leading photovoltaic technologies. Efficiency improvements in the past decade made it a very attractive and practical source of renewable energy. Considering the theoretical limit, there is still room for improvement, especially the cell’s open circuit voltage (VOC). To improve VOC, the p-type carrier concentration and minority carrier lifetime of the CdTe absorber needs to be improved. Both these parameters are directly related to the point defect distribution of the semiconductor, which is a function of deposition stoichiometry, dopant incorporation and post-deposition treatments.

CdTe films were deposited by the Elemental …

Plasma-Induced Amorphous Shell And Deep Cation-Site S Doping Endow Tio2 With Extraordinary Sodium Storage Performance, Hanna He, Dan Huang, Wei Kong Pang, Dan Sun, Qi Wang, Yougen Tang, Xiaobo Ji, Zaiping Guo, Haiyan Wang

Australian Institute for Innovative Materials - Papers

Structural design and modification are effective approaches to regulate the physicochemical properties of TiO 2 , which play an important role in achieving advanced materials. Herein, a plasma-assisted method is reported to synthesize a surface-defect-rich and deep-cation-site-rich S doped rutile TiO 2 (R-TiO 2- x -S) as an advanced anode for the Na ion battery. An amorphous shell (≈3 nm) is induced by the Ar/H 2 plasma, which brings about the subsequent high S doping concentration (≈4.68 at%) and deep doping depth. Experimental results and density functional theory calculations demonstrate greatly facilitated ion diffusion, improved electronic conductivity, and an increased …

Effect Of Al And Ga Codoping On The Morphological, Electronic, And Opticalproperties Of Zno Transparent Conductive Thin Films Prepared By Spray Pyrolysistechnique, Worapot Sripianem, Ratchatee Techapiesancharoenkij

Turkish Journal of Physics

Codoping a semiconductor thin film with two or more dopants is a feasible technique to improve the electrical properties of the thin film. In this work, we studied the codoping of Al and Ga n-type impurities in a ZnO film (AGZO) deposited on a glass substrate by the spray pyrolysis method. The total doping concentration, [Al + Ga]/[Al + Ga + Zn], was 5 at.% with varying Al:Ga codoping proportions of 0:5, 1.25:3.75, 2.5:2.5, 3.75:1.25, and 5:0 at.%. The effect of Al/Ga codoping on the structural, texture, morphological, optical, and electrical properties of the AGZO films were investigated using X-ray …