I am (mainly!) an experimental material scientist by training, but I also have aquired a bit of an interest in computational condensed matter physics. In the following paragraphs, I describe all the research projects performed in my lab:
I. Experimental Projects:
1. Thermoelectric Properties of Manganese Oxide Powders and Thin Films (perfomed in its entirety at JMU)
Due to the ever-increasing energy demand and growing global concern over the environmental impact of carbon dioxide emissions, there is an
urging need to seek solutions to transit from fossil fuels to sustainable energy. Only 30% of the energy we use everyday is converted into
useful work and the remaining 70% is wasted as dissipated heat during energy conversion, transportation and storage. This giant loss is itself
a source of recyclable energy that can be renewed into useful energy. Thermoelectric (TE) materials show great promise for converting waste heat
energy into electricity. TE systems have many unique advantages such as silent operationality, time reliability, and dimensional scalability.
Most recently, researchers found that MnO2 nanoparticles show a giant Seebeck coefficient of S = 20 mV/K, which is 100 times
higher than bismuth telluride, one of the best TE materials. However, no information it has been provided regarding the Figure of Merit (ZT) or
thermal conductivity of this material. Therefore, it is very important to study the interplay between ZT, electrical conductivity, packing
density and the particle size. We are also in the process of characterizing the thermoelectric properties of MnO2 thin films deposited by Magnetron Sputtering deposition technique.
2. Conductivity and Thickness Characterization of Sulfuric Acid Treated PEDOT:PSS Films (perfomed in its entirety at JMU)
In recent years, high conductivity transparent materials have gained more attention in material science. These transparent conducting materials are important components in a number of various electronic devices such as: computer and TV displays, mobile phones, handheld game consoles, touchscreens, and solar cells. The most popular material used today is Indium Tin Oxide (ITO). Though ITO has a high electrical conductivity and optical transparency, indium is expensive, and very hard to find. ITO is also ceramic in nature and therefore brittle. Poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) films have been investigated as a suitable alternative to Indium Tin ITO films. PEDOT:PSS has a conductivity comparable to that of ITO and its price is much more reasonable. When PEDOT:PSS films are treated with sulfuric acid, an increased conductivity was seen as the acid treatment time was increased. Our group also noticed that there is a change in the film thickness post acid treatment and we are in the process of quantizing the loss in thickness as a function of acid treatment.
3. Thermal Transport Across Metal/Semiconductor, Metal/Polymer Interfaces (performed in collaboration with performed in collaboration with Dr. Patrick Hopkins from University of Virginia, VA)
As device dimensions become smaller and smaller with time (Moore's Law), pushing the limits of typical functionality, the thermal
properties of devices become more governed by the heat transfer across material interfaces than in the matter themselves.
Therefore, it is increasingly important to study the thermal boundary conductance (i.e., Kapitza conductance) of interfaces to fully
understand and engineer the thermal transport in next generation nanodevices. For example, in the presence of a heat flux across a
solid-solid interface between a GaN film and another thin film or substrate (i.e., Al2O3), there is a finite thermal boundary resistance
which will cause a thermal discontinuity at this interface. Therefore, the behaviour of Kapitza conductance at the interface is of utmost importance. Over the years, our research group at JMU worked closely with Prof. Patrick Hopkins from U.Va. to understand Kapitza conductance of GaN deposited on Sapphire as a function of surface roughness. We are also in the process of determining Kapitza conductance of sulfuric acid treated PEDOT:PSS thin films.
II. Computational Projects:
3. Proximity Induced Magnetism In Transition Metal Substituted Graphene (performed in collaboration with Dr. Jason Haraldsen from University of North Florida, FL)
We use density functional theory (DFT) to study the change in the electronic and magnetic properties of transition-metal subsituted graphene. We start with a 128-atom supercell of graphene and replace two, three, or four carbon atoms with either vanadium, chromium, or manganese. Then, we perform DFT calculations to determine the total energy ground state, electronic band structure, density of states, and magentic moment for each spin configuration. Our results show that the presence of magnetic atoms induces a magnetic state in the neighboring carbon atoms.
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