Structural and Electrical Characterization of Amorphous and Crystalline Manganese Oxide Thin Films Deposited by DC Magne
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Structural and Electrical Characterization of Amorphous and Crystalline Manganese Oxide Thin Films Deposited by DC Magnetron Sputtering David H. Olson1, Kenneth D. Shaughnessy1, Emma G. Langford2, Michael Boyle1, Muhammad B. Haider3, David Lawrence4, Costel Constantin1 1 Department of Physics and Astronomy, James Madison University, Harrisonburg, VA 22807 2 Department of Chemistry, James Madison University, Harrisonburg, VA 22807 3 Department of Physics, King Fahd University of Petroleum & Minerals, Dhahran 34464, Saudi Arabia 4 Department of Integrated Science and Technology, James Madison University, Harrisonburg, VA 22807 ABSTRACT The environmental impact resulting from the use of fossil fuel as an energy source affects the entire globe. Eventually, fossil fuels will no longer be a reasonable source of energy and alternative energy sources will be needed. Thermoelectric materials (TE) that directly convert heat into electricity are a viable option to replace the conventional fossil fuel because they are reliable, cost effective, and use no moving parts. Recently researchers discovered the existence of giant Seebeck coefficient in manganese oxide (MnO2) powders, which ignited an increased interest in MnO2-based materials. In this work we present a systematic structural and electrical characterization of amorphous and crystalline MnxOy thin films. These films were deposited at room temperature on heated silicon and sapphire substrates by DC Magnetron Sputtering. Our preliminary results show that MnxOy/silicon thin films undergo a crystalline change from Mn2O3 to Mn3O4 as annealing temperature is increased from 300ºC to 500ºC. INTRODUCTION The Fossil fuels used as an energy source are more and more environmentally incompatible and already affect the entire globe. Eventually, fossil fuels will no longer be a reasonable source of energy, and alternative energy sources will be needed. Thermoelectic (TE) materials that directly convert heat into electricity are a viable option to replace the conventional fossil fuels because they are reliable, cost effective, and use no moving parts. The efficiency of a TE material is defined by the dimensionless figure of merit, ZT = (σ ⋅ S 2 ⋅T ) / (κ E + κ P ) where S is the Seebeck coefficient, σ is the electrical conductivity, T is the temperature, and kE and kP are the carrier and phonon thermal conductivities, respectively. One of the most known and commercially available TE materials is bismuth telluride (Bi2Te3), which exhibits one of the highest ZT values at room temperature (i.e., ZT ~1). Thermoelectric devices (TED) made out of Bi2Te3 are already commercially available and are used for small scale energy harvesting [1]. However, one of the main drawbacks of Bi2Te3 is the fact that it is poisonous. Transition metal oxides (TMO) are attractive materials for replacing Bi2Te3 because they are non-toxic, inexpensive, withstand high temperature, and have minimal impact on the environment [2]. In particular, manganese dioxide (MnO2)-based materials are of great interest for various
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