Fluence Dependence of Thermoelectric Properties Induced By Ion Bombardment of Zn4Sb3 and CeFe2Co2Sb12 thin films
- PDF / 136,030 Bytes
- 5 Pages / 612 x 792 pts (letter) Page_size
- 36 Downloads / 249 Views
1020-GG07-18
Fluence Dependence of Thermoelectric Properties Induced By Ion Bombardment of Zn4Sb3 and CeFe2Co2Sb12 thin films C. C. Smith1, S. Budak2, S. Guner2, C. Muntele2, R. A. Minamisawa2, R. L. Zimmerman2, and D. ILA2 1 MSFC, NASA, MSFC, Huntsville, AL, 35812 2 Center for Irradiation of Materials, Alabama A&M University, 4900 Meridian Street, PO Box 1447, Normal, AL, 35762 Abstract Thermoelectric power generation is a promising technology for increasing the efficiency of electrical and optical electrical devices. We prepared samples by Electron Beam evaporated Zn4Sb3 and CeFe2Co2Sb12 thin films on silicon dioxide (silica) substrates. The materials were co-evaporated and then were prepared for gold over-coating. Following electron deposition we performed post ion bombardment at a constant energy of 5 MeV while varying fluence from 1x1012, 1x1013, 1x1014, 1x1015 ions/cm2, respectfully. The production of nano-clusters generated by the MeV Si ions bombardment modifies the electrical and phonon interactions in the materials. Also, we will report on the fluence dependence of the figure of merit, Seebeck coefficient, thermal conductivity and electrical conductivity. In addition, Rutherford backscattering spectrometry (RBS) was used to analyze the elemental composition and the thickness of the deposited material. *Corresponding author: D. ILA; Tel.: 256-372-5866; Fax: 256-372-5868; Email: [email protected] 1. INTRODUCTION Processing thermo electric materials into thin films allows for unique devices that would be difficult to process using bulk materials [1]. The efficiency of the thermoelectric devices is determined by the figure of merit ZT [2]. The figure of merit is 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 [3,4]. ZT can be increased by increasing S, increasing σ, or decreasing κ. Efficient thermoelelctric devices have a high electrical conductivity and a low thermal conductivity [5]. Our investigation focuses on the development of nano structures and thin films of previously investigated bulk materials. Our goal is to process films with the following properties: Low thermal conductivity, high electrical conductivity and a high figure of merit.
2. EXPERIMENTAL Zn4Sb3 and CeFe2Co2Sb12 thin films were prepared using an ion beam assisted deposition (IBAD) system. In the preparation process of Zn4Sb3, Zn and Sb were placed in the two separate Telemark Electron gun evaporators and were co-evaporated to form the thin film of Zn4Sb3. In the preparation process of CeFe2Co2Sb12, Ce, Fe and Co were placed in one of the two separate Telemark Electron gun evaporators while Sb was placed in the other electron gun evaporator and they were co-evaporated to form the thin film of CeFe2Co2Sb12. The base pressure for both the depositions was 6.0x 10-6 torr. The thickness of the films was controlled by an INFICON deposition monitor. The film geometries used in this study are shown in Fig.1. Fig.1a shows the geometry of Zn4S
Data Loading...
