Fabrication and Characterization of Thermoelectric Generators From SiO 2 /SiO 2+ Au Nano-layered Superlattices
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Fabrication and Characterization of Thermoelectric Generators From SiO2/SiO2+Au Nano-layered Super-lattices M. Pugh1, R. Hill1, B. James1, H. Martin1, C. Smith2, S. Budak1*, K. Heidary1, C. Muntele2, D. ILA2 1-Department of Electrical Engineering, Alabama A&M University, Normal, AL USA 2-Center for Irradiation of Materials, Alabama A&M University, Normal, AL USA
Abstract The efficiency of the thermoelectric devices is limited by the properties of n- and p-type semiconductors. Effective thermoelectric materials have a low thermal conductivity and a high electrical conductivity. The performance of the thermoelectric materials and devices is shown by a dimensionless figure of merit, ZT = S2σT/K, where S is the Seebeck coefficient, σ is the electrical conductivity, T is the absolute temperature and K is the thermal conductivity. In this study we prepared the thermoelectric generator device of SiO2/SiO2+Au multi-layer super-lattice films using the ion beam assisted deposition (IBAD). In order to determine the stoichiometry of the elements of SiO2 and Au in the grown multilayer films and the thickness of the grown multi-layer films Rutherford Backscattering Spectrometry (RBS) and RUMP simulation software package was used. The 5 MeV Si ion bombardments was performed to make quantum clusters in the multilayer super-lattice thin films to decrease the cross plane thermal conductivity, increase the cross plane Seebeck coefficient and cross plane electrical conductivity. To characterize the thermoelectric generator devices before and after Si ion bombardments we measured the cross-plane Seebeck coefficient, the cross-plane electrical conductivity, and the cross-plane thermal conductivity for different fluences. Keywords: Ion bombardment, thermoelectric properties, multi-nanolayers, Figure of merit. *Corresponding author: S. Budak; Tel.: 256-372-5894; Fax: 256-372-5855; Email: [email protected] M. Pugh, R. Hill, B. James, H. Martin are 2008-2009 Senior Design Project Students in the Department of Electrical Engineering in Alabama A&M University. 1. INTRODUCTION Thermoelectric materials are being increasingly important due to their applications in thermoelectric power generation and micro electronic cooling devices [1]. Thermoelectric devices do not have moving parts and do not generate greenhouse gases. The efficiency of the thermoelectric devices is limited by the material properties of n-type and p-type semiconductors [2]. The best thermoelectric materials were succinctly summarized as “phonon-glass electron-crystal” (or PGEC in short), which means that the materials should have a low lattice thermal conductivity as in glass, and high electrical conductivity
as in crystals [3]. The efficiency of the thermoelectric devices is determined by the figure of merit ZT [4]. The figure of merit is defined by ZT = S 2σT / κ , where S is the Seebeck coefficient, σ is the electrical conductivity, T is the absolute temperature, and κ is the thermal conductivity [5, 6]. ZT can be increased by increasing S, by increasi
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