High power factor due to multi-scale engineering in ultra-thin bismuth telluride films

High thermoelectric (TE) power factors were obtained for bismuth telluride by deploying confinement and multi-scale engineering in synergy. The thickness of the film was kept in the ultra-thin range (41 nm) following which a high magnitude of 1.9 × 104 S m−1 was obtained at room temperature (RT). Fi...

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Bibliographic Details
Published in:Journal of applied physics 2020-09, Vol.128 (12)
Main Authors: Singh, Sukhdeep, Tripathi, S. K.
Format: Article
Language:English
Subjects:
Alloying
Antisite defects
Applied physics
Bismuth tellurides
Crystal defects
Crystallites
Electrical resistivity
Grain boundaries
Grain growth
High temperature
Intermetallic compounds
Power factor
Room temperature
Seebeck effect
Substrates
Tellurium
Temperature
Thickness
Thin films
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Summary:High thermoelectric (TE) power factors were obtained for bismuth telluride by deploying confinement and multi-scale engineering in synergy. The thickness of the film was kept in the ultra-thin range (41 nm) following which a high magnitude of 1.9 × 104 S m−1 was obtained at room temperature (RT). Films were deposited at an elevated substrate temperature to enhance the grain quality and high mobility bearing (00l) grain growth. Thus, relatively large crystallite sizes (∼26 nm) with less grain boundaries and directional growth with a low defect profile were the prime reasons for highly enhanced electrical conductivity. Apart from the multiple effects that were deployed, ultra-thin dimensions of the films proved to be effective in further enhancing Seebeck coefficient values. The co-alloyed In minimized the hole concentration through reducing antisite defects and also preserved the reduced bipolar effect at elevated temperatures. The inclusion of excess tellurium induced Te segregates in the film that helped in energy dependent scattering of carriers in addition to its donor-like effect. Hot carrier filtering, induced by excess Te along with ultra-thin dimensions resulted in a Seebeck coefficient (S) of −223.6 μV K−1 at RT. A soaring value of −338.1 μV K−1 was obtained at 90 °C. Following the synergetic employment of multiple enhancement strategies, a high power factor of 959.9 μW m−1 K−2 was obtained at room temperature with a towering magnitude of 2537.7 μW m−1 K−2 at 90 °C.
ISSN:0021-8979
1089-7550
DOI:10.1063/5.0010380