Thermoelectric Properties of YbBiPt and YBiPt Thin Films
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1100-JJ04-22
Thermoelectric Properties of YbBiPt and YBiPt Thin Films Sadik Guner1,2, Satilmis Budak3, Claudiu I Muntele1, and Daryush Ila1 1 Physics, Alabama A&M University, Center for Irradiation of Materials, 4900 Meridian street, Normal, AL, 35762 2 Department of Physics, Fatih University, Hadimkoy, Buyukcekmece, Istanbul, 34500, Turkey 3 Electrical Engineering, Alabama A&M University, 4900 Meridian Street, Normal, AL, 35762 Abstract Monolayer thin films of YbBiPt and YBiPt have been produced with 560 nm and 394 nm thick respectively in house and their thermoelectric properties were measured before and after MeV ion bombardment. The energy of the ions were selected such that the bombarding Si ions stop in the silicon substrate and deposit only electronic energy by ionization in the deposited thin film. The bombardment by 5.0 MeV Si ions at various fluences changed the homogeneity as well as reducing the internal stress in the films thus affecting the thermal, electrical and Seebeck coefficient of thin films. The stoichiometry of the thin films was determined using Rutherford Backscattering Spectrometry, the thickness has been measured using interferometry and the electrical conductivity was measured using Van der Pauw method. Thermal conductivity of the thin films was measured using an inhouse built 3ω thermal conductivity measurement system. Using the measured Seebeck coefficient, thermal conductivity and electrical conductivity we calculated the figure of merit (ZT). We will report our findings of change in the measured figure of merit as a function of bombardment fluence. Keywords: Ion bombardment, thermoelectric properties, Rutherford Backscattering, Van der Pauw method, 3ω method, Seebeck coefficient, Figure of merit. *Corresponding author: S. Guner; Tel.: 256-372-8413; Fax: 256-372-5868; Email: [email protected]
1. INTRODUCTION One of the important issues relative to the development of low-temperature thermoelectric materials is the identification of mechanisms, which might give high thermopower at low temperatures. Possibilities include phonon drag, heavy fermion materials, Kondo systems, (Kondo Systems and Heavy Fermions: Transport Phenomena) and material that exhibit phase transitions, as well as quasi-one dimensional materials [1]. The cubic YBiPt compound crystallizes in the MgAgAs cubic structure so called as Heusler alloys. The study of this compound has become very important since the discovery by Canfield and coworkers that the compound YbBiPt is a cubic heavy fermion which has the largest known linear specific heat coefficient, γ= 8 J mol-1K-2 which is an order of magnitude larger than that of typical heavy fermions and three orders of magnitude greater than that of
conventional metals [2,3]. The thermoelectric properties of this kind semi-metallic compounds are of interest of the researchers [1]. The efficiency of the thermoelectric devices is determined by the dimensionless figure of merit ZT [4]. The dimensionless figure of merit is calculated by ZT = S 2σT / κ , where S is the Seebeck
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