Seminar Series

Speaker Sam Uba

Day and Time: Tuesday, April 30, 2019

Place: Room 130 VMC

 Abstract

 In this research, we propose the use of the perturbation method to solve the nonlinear Klein Gordon equation. The perturbation method is a useful mathematical tool for finding approximate analytic solutions to problems whose analytic solution cannot be found. The multi-scales method a type of the perturbation approximation is utilized to solve problems such as the nonlinear Klein Gordon equation whose analytical solution yields secular terms in the asymptotic expansion solution leading to a breakdown. We have analyzed the perturbation effect on the solution of the wave equation as it relates to condensed matter physics and compared the validity of our solution to other analytic methods.

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Speaker: Dr. Satilmis Budak
Day and time: Friday, November 9, 2018 at 12:30 pm.
Place: room 130 VMC

Abstract

Electron spin resonance (ESR) measurements have been carried out on colossal magnetoresistive (La0.67Ca0.33)MnO3 and Fe3O4 thin films. (La0.67Ca0.33)MnO3 thin films were deposited by pulsed laser deposition. Fe3O4 thin films were deposited by RF sputtering. The Fe3O4 films have been studied as a function of temperature. The effect of surface coating (Co and CoxOy) has also been studied. The ESR spectra of (La0.67Ca0.33)MnO3 at low temperature were seen to consist of overlapping low energy spin wave resonance (SWR) modes excited across opposite surfaces of the film. The magnetic anisotropies of Fe3O4 thin films are strongly affected both by film thickness and surface coating conditions at room temperature. Magneto-crystalline cubic anisotropy is much smaller compared to its value for the bulk sample of the same compound. For the low temperature measurements, Verwey transition for thin film case was found to shift down to around 90 K from 120 K for bulk sample of the same compound.

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Speaker: Dr. Ashok Batra
Date: Friday October 19, 2018
Time: 12:30 pm
Room: 130 VMC

Abstract

In this talk. Dr. Batra will introduce you to “Smart Materials , their Physics of Operation and Applications in all Walks of Life”. He will also briefly describe the recent preliminary results obtained of research being started in his group in the arena of mimicking motion of recovering arm, including a first novel prototype designed and fabricated for generating electric energy in moving vehicles. Test results obtained may also be presented while driving a car along the AAMU Quad.

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Speaker: Dr. Matthew Edwards
Date and time: May 31, 2018 at 1:00 pm
Place: 130 VMC

Abstract

Analytical solutions for the Schrodinger equation can be obtained easily for single particle or effectively single particle problems. Such solutions, even under the greatest effort, have not been achievable for systems of two or more interacting particles thus, rendering little to no productivity in condensed mater physics at the first principle level. To address this shortcoming, several many-body approaches using variations to the Schrodinger equation have been developed to consider quantum-mechanical systems having coulombic or other interacting potentials. The Density Functional theory, as we present here, is an approximation method that has enjoyed considerable success. Upon recognizing the similarity between the solvable single particle Schrodinger equation and Kohn-Sham equation, including potentials to represent interactive effects, the complete N-bodies Schrodinger equation can be replaced by N-one body equations, thereby yielding reasonable solutions under the umbrella of Density Functional theory. The theory provides a method to solve effectively the many-body Schrodinger equation that exists in condensed mater physics. Here, we present our recent developments at achieving meaningful results for dielectric and pyroelectric thin films regarding energy harvesting, energy storage, and sensor science. Additionally, we present perturbation effects on 1-soliton solutions of the relativistic Klein Gordon equation in nonlinear media. We observe that perturbation terms do exist, and their influences can control the soliton’s motion, even to the extent of altering its velocity.

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Speaker: Dr. Ashok Batra
Date: Thursday, April 26, 2018
Time: 1 pm Room: 130 VMC

Abstract

Materials Science Group of Dept. of Physics, Chemistry and Mathematics has been active in the diverse areas: Growth of Crystals of technological importance; uncooled wide band Pyroelectric Infrared detectors; Electronic transport properties of materials; Thick films; Thin Films; Organic solar cells; Theoretical modeling of a number of devices; Electronic ceramics; Smart nano-composites (Cement-, polymer- and paint- based); Ambient energy harvesting via piezoelectricity and pyroelectricity; Mentoring undergraduate students; and Development of applied materials science courses. Dr. Batra will walk through all these activities via posters. Next formal presentation by him will be after summer break

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Speaker: Satilmis Budak
Date: March 22, 2018 Time: 1:00 pm
Place: 130 VMC 

Abstract

Thermoelectric devices could convert heat difference to the electricity. The efficiency of the thermoelectric materials and the devices is shown by the dimensionless figure of merit, ZT. ZT is calculated by multiplying the square of Seebeck coefficient with the electrical conductivity and absolute temperature dividing it all by its thermal conductivity. Thermoelectric devices from the multilayered heterostructured Si/Si+Sb and Si/Si+Ge thin films were deposited using DC/RF Magnetron Sputtering system. They were modified with thermal annealing at different temperatures to form quantum structures in the multilayers to increase both the electrical conductivity and the Seebeck coefficient and decrease the thermal conductivity to reach higher ZT. Seebeck coefficients, van der Pauw-four probe resistivity, Laser PIT thermal conductivity measurement systems have been used for characterization. Some remarkable results were reached due to the effects of the heat treatments at different temperatures. Si/Si+Sb, Si/Si+Ge multilayer devices reached their highest ZT of 2.6, 0.37, respectively at some annealed temperatures.

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Speaker: B. Rami Reddy

Date: February 15, 2018 Time: 1 to 2 pm
Place: 130 VMC

Abstract

Rare-earth ion doped crystals and glasses are investigated for white light emission studies under diode laser excitation. Chromaticity diagrams, color coordinates and color temperature are estimated. These materials meet the criteria of white light emitters.

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Speaker: Dr. Ashok Batra

Date: Thursday, November 16, 2017
Time: 2 pm
Room: 130 VMC

Abstract

Throughout history, people have designed and shaped materials at hand. With better understanding of material properties came the ability to fabricate materials with designed characteristics for specific applications. Currently, a materials category that is experiencing extensive research and development and some applications is “Smart Materials” . Dr. Batra will expand on smart materials and their applications based on various concepts.

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Speaker: Dr. Matthew E. Edwards

Thursday, October 19, 2017 @ 1 pm
Place: Room 130 VMC

Abstract

The Schrodinger equation provides basic physics concepts of elementary non-relativistic quantum mechanics of electrons in problems such as a harmonic oscillator, a particle in a box, and the electron in the hydrogen atom. Critically absent in the Schrodinger equation is the electron spin operator, which directly expresses spin-related properties. This aspect of an electron is added in an ad-hoc manner through the Hamiltonian operator in special applications, such as when an electron is moving in a magnetic field. In addition, the Schrodinger does not include the special theory of relativity aspects to particle behavior, which is required when two or more particles are involved, as when a single electron is bounded to a nucleus, or when multiple electrons and nuclei are interacting as in condensed matter physics. To that extent, three other theoretical equations exist in quantum mechanics to include the spin, relativity, or both phenomena. First, the Klein-Gordon equation, a second-order differential equation in both time and space, is the relativistic extension of the Schrodinger equation for zero spin particles. Secondly, when considering non-relativistic spin effects, the Schrodinger equation is extended to Pauli's equation, and thirdly, with both attributes, spin and relativity, the first-order differential matrix Dirac Equation has been developed. Each of these four equations provides its individual attributes to density functional theory calculations in condensed matter physics for the theories of dielectric, pyroelectric and piezoelectric composite materials. In this regard, we show, in this first part of a three-part series of presentations, how to derive and solve through Finite-element Methods and Mathematica the important, single-particle Kohn-Sham equation of density function theory. Additionally, we introduce non-linear aspects in the above four quantum mechanical differential equations, show how solitons solutions can be manifested, and illustrate their relevance to the composite materials that we are studying.

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Speaker: Dr. Satilmis Budak

Thursday, Sept 14, 2017 @ 1 pm
Place: Room 130 VMC

Abstract

The efficiency of the thermoelectric materials and devices is shown by the dimensionless figure of merit, ZT. ZT is calculated by multiplying the square of Seebeck coefficient with the electrical conductivity and absolute temperature dividing it all by its thermal conductivity. The thermoelectric devices were prepared using different multilayer thin film structures of SiO2/Au and Ni/Bi2Te3/Sb2Te3/Ni using the E-Beam and the DC/RF magnetron sputtering systems. The prepared thermoelectric devices have been tailored with thermal annealing at different temperatures to form quantum structures in the multi-layer thin films to increase both the electrical conductivity and Seebeck coefficient and decrease the thermal conductivity to reach high figure of merit, ZT. For characterization and measurements; Seebeck coefficients, van der Pauw-four probe resistivity, Laser PIT thermal conductivity, Hall Effect coefficient, density and mobility measurements have been performed. SEM/EDS have been used to exhibit the effects of the thermal treatment on the fabricated thermoelectric devices. Thermal treatment at suitable temperatures caused improvements on the thermoelectric properties of the fabricated thin film devices.

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Speaker: Ashok Batra

Date: May 25, 2017 (Thursday)
Time: 1:00 pm
Place: Room 130 VMC

Abstract

The Earth receives from solar radiation in 10 days as much energy as the known fossil reserves. Thus, conversion of solar energy to electricity is required for the society to survive. The important, viable and cost-effective mode of conversion is via Solar Cells. In this talk, presenter will walk you through various applications where solar cells are being used in a unique way.

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Speaker: Dr. Satilmis Budak

Place: Physics Library (Room 137 VMC)
Date and Time: Thursday, April 13, 2017; 11:00am – 12:00 pm

Abstract

Single crystalline tin oxide (SnO2) nanowires have been synthesized by the carbothermal reduction of SnO2 nanopowder followed by thermal evaporation of the reduced precursor and growth via the vapor–liquid–solid (VLS) growth mechanism. The nanowires are deposited on amorphous SiO2 and single-crystalline Al2O3 and TiO2 substrates of different orientations that are coated with a thin film of gold catalyst. While the SnO2 single crystal nanowires grow randomly oriented on SiO2, they exhibit a definite epitaxial relationship for growth on lattice-matched Al2O3 and TiO2 substrates. Selective-area growth of the nanowires in specific regions of the substrates has been accomplished by lithographically patterning the Au catalyst layer. For nanowires deposited on (1 0 0) and (1 1 0)-oriented TiO2substrates, the morphology of nanowires is sensitively dependent on the growth direction and also on the substrate-precursor distance. By using gold colloids with a narrow size distribution, instead of a thin film, monodisperse SnO2 nanowires that are well isolated have been synthesized.

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Speaker: Dr. B. Rami Reddy

Place: Physics Library (Room 137 VMC)
Date and Time: Tuesday, March 21, 2017; 11:00am – 12:00 pm

Abstract

Optical hole burning is a high-resolution spectroscopy technique that has applications to optical data storage in addition to obtaining fundamental knowledge of the materials. In this lecture I will describe the homogeneous and inhomogeneous broadenings of the spectral lines. The hole burning mechanisms in crystals, glasses and polymers will be described. A brief explanation of the optical memory concept will be provided.

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Speaker: Dr. Ashok Batra

Place: Physics Library (Room 137 VMC)
Date and Time: Thursday, February 16. 2017 ; 1:00 – 2:00 pm

Abstract

Enhanced urbanization and industrialization has necessitated use of distributed miniaturized sensors for persistent observation of gases and various other contaminants that may be harmful to our well-being. Several metal Oxide viz., SnO2, ZnO, TiO2,WO2,Ga2O3, are examined for gas sensing applications for environmental contaminants with applications ranging from monitoring of industrial emission process to heavily populated urban settings. In the presentation; an overview of all major class of micro-and nano chemical sensors will be described. The result of our investigation on thick-film sensors based on binary mixtures of oxides; Tin oxide/Zinc oxide; Tin oxide/Indium oxide; Tin oxide/Tungsten oxide; and their response in terms of sensitivity and response time to 2-isopropanol will be presented along with details of fabrication technique utilized.

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Place: Physics Library (Room 137 VMC)
Date and Time: Thursday, January 19, 2017 ; 1:00 – 2:00 pm

Abstract

Thermoelectric devices were prepared from Ni/Bi2Te3/Ni and Ni/Sb2Te3/Ni thin films using DC/RF magnetron sputtering and E-beam deposition systems. Thermoelectric devices were annealed at different temperatures to form nanostructures in the multilayer thin films to increase both the Seebeck coefficient and electrical conductivity and decrease thermal conductivity. The thin film devices were characterized using Seebeck coefficient measurement systems; four probe van der Pauw measurement system to measure resistivity, sheet resistance, density, mobility and type of the charge carrier concentration. In addition to the Seebeck coefficient and van der Pauw measurements, the laser thermal conductivity system was used for the thermal conductivity measurements. The surface morphology of the fabricated thermoelectric films is characterized using Scanning Electron Microscope (SEM).

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Speaker: Dr. Rami Reddy

Place: Physics Library (Room 137 VMC)
Date and Time: Thursday, November 17, 2016 ; 1:00 – 2:00 pm

Abstract

When a laser beam passes through a laser material its temperature changes along the beam path. In most materials the temperature increases. However, in some materials the temperature decreases. The later phenomenon is used in the design of vibration-free cooling modules for imaging cameras. For diagnostic purposes one has to measure the temperature change. Here I will describe the application of heterodyne technique for the measurement of changes in temperature.

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Speaker: Dr. Matthew Edwards

Place: Physics Library (Room 137 VMC)
Date and Time: Thursday, October 20, 2016 ; 1:00 – 2:00 pm

Abstract

Previously, we have reported measurements of the temperature-dependent surface resistivity of pure and multi-walled carbon nanotubes doped Polyvinyl Alcohol (PVA) thin films. In the temperature range from 22 0C to 40 0C, near room temperature, with a humidity-controlled environment, we found the surface resistivity to decrease initially but to rise steadily as the temperature continued to increase. Additionally, electric surface current densities Js were measured on the surface of pure and MWCNT doped PVA thin films, and were found, differently than initially surmised, to be produced through ohmic conduction or space-charge conduction, as the two are indistinguishable at low voltages yielding a surface-limited conduction phenomenon only. Finally, we present conventional volume resistivity measurements in the same temperature range, and it was recognized that nano-dopants, microscopic structure, and environmental conditions contributed to the unique physical properties of these material systems.

Keywords: Surface and Volume Currents, Surface and Volume Resistivity, Multi-walled Carbon Nanotubes (MWCNT), PVA thin films

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Speaker: Dr. Matthew Edwards

Place: Physics Library (Room 137 VMC)
Date and Time: Thursday, September 22, 2016 ; 1:00 – 2:00 pm

Abstract

Physics is considered by some to be the most perplexing area in the sciences and perceived as a hard subject for students from secondary school to the university to adult-graduate education. Educational research has provided evidence that attitudes towards physics and the valuing of it change with exposure to it. When students have negative attitudes towards physics, they often do not “like” physics courses or the teachers of those courses. Based on this premise, numerous studies have been conducted to determine the factors that affect students’ attitudes towards physics. A goal that is important to most if not all teachers of physics courses is to inspire students to have a positive attitude towards the subject. This goal encompasses an appreciation of how physicists think and how they incorporate the values that it provides, as well as, how it is applied to other areas or related fields, and its application in everyday life. In this regard, the aim of this investigation has been to explore how to impact more effectively positive students’ attitudes in physics courses. To that end, we report the effectiveness of a constructivistic multimedia-learning package (MLP) in shaping and guiding students’ attitudes towards physics and how valuing the subject is critically involved.

Keywords: Constructivist, Multi-media Learning Package (MLP), Bloom’s Cognitive Domain, Bloom’s Affective Domain, Valuing

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