Enhanced thermoelectric properties of phase-separating bismuth selenium telluride thin films via a two-step method
- Department of Materials Science, Tokai University, 4-1-1 Kitakaname, Hiratsuka, Kanagawa 259-1292 (Japan)
- Department of Mechanical and Control Engineering, Kyushu Institute of Technology, 1-1 Sensui, Tobata-ku, Kitakyushu 804-8550 (Japan)
- Department of Mechanical Engineering, College of Engineering, Nihon University, 1 Nakagawara, Tokusada, Tamuramachi, Koriyama, Fukushima 963-8642 (Japan)
A two-step method that combines homogeneous electron beam (EB) irradiation and thermal annealing has been developed to enhance the thermoelectric properties of nanocrystalline bismuth selenium telluride thin films. The thin films, prepared using a flash evaporation method, were treated with EB irradiation in a N{sub 2} atmosphere at room temperature and an acceleration voltage of 0.17 MeV. Thermal annealing was performed under Ar/H{sub 2} (5%) at 300 °C for 60 min. X-ray diffraction was used to determine that compositional phase separation between bismuth telluride and bismuth selenium telluride developed in the thin films exposed to higher EB doses and thermal annealing. We propose that the phase separation was induced by fluctuations in the distribution of selenium atoms after EB irradiation, followed by the migration of selenium atoms to more stable sites during thermal annealing. As a result, thin film crystallinity improved and mobility was significantly enhanced. This indicates that the phase separation resulting from the two-step method enhanced, rather than disturbed, the electron transport. Both the electrical conductivity and the Seebeck coefficient were improved following the two-step method. Consequently, the power factor of thin films that underwent the two-step method was enhanced to 20 times (from 0.96 to 21.0 μW/(cm K{sup 2}) that of the thin films treated with EB irradiation alone.
- OSTI ID:
- 22494734
- Journal Information:
- Journal of Applied Physics, Vol. 118, Issue 6; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ANNEALING
ARGON
BISMUTH TELLURIDES
CONTROLLED ATMOSPHERES
CRYSTALS
ELECTRIC CONDUCTIVITY
ELECTRIC POTENTIAL
ELECTRON BEAMS
ELECTRON TRANSFER
EVAPORATION
IRRADIATION
MEV RANGE
MOBILITY
NANOSTRUCTURES
POWER FACTOR
SELENIUM
SELENIUM TELLURIDES
TEMPERATURE RANGE 0273-0400 K
THERMOELECTRIC PROPERTIES
THIN FILMS
X-RAY DIFFRACTION