Thermoelectric properties of Bi₁âx̳Sbx̳ nanowires and lead salt superlattice nanowires
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2003.
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| Format: | Thesis |
| Language: | eng |
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Massachusetts Institute of Technology
2005
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| Online Access: | http://hdl.handle.net/1721.1/17593 |
| _version_ | 1826190870125215744 |
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| author | Lin, Yu-Ming, 1974- |
| author2 | Mildred S. Dresselhaus and Jackie Y. Ying. |
| author_facet | Mildred S. Dresselhaus and Jackie Y. Ying. Lin, Yu-Ming, 1974- |
| author_sort | Lin, Yu-Ming, 1974- |
| collection | MIT |
| description | Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2003. |
| first_indexed | 2024-09-23T08:46:52Z |
| format | Thesis |
| id | mit-1721.1/17593 |
| institution | Massachusetts Institute of Technology |
| language | eng |
| last_indexed | 2024-09-23T08:46:52Z |
| publishDate | 2005 |
| publisher | Massachusetts Institute of Technology |
| record_format | dspace |
| spelling | mit-1721.1/175932019-04-10T07:30:42Z Thermoelectric properties of Bi₁âx̳Sbx̳ nanowires and lead salt superlattice nanowires Lin, Yu-Ming, 1974- Mildred S. Dresselhaus and Jackie Y. Ying. Massachusetts Institute of Technology. Dept. of Electrical Engineering and Computer Science. Massachusetts Institute of Technology. Dept. of Electrical Engineering and Computer Science. Electrical Engineering and Computer Science. Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2003. In title on t.p., double-underscored "x" appears as subscript. Includes bibliographical references (p. 138-147). This thesis involves an extensive experimental and theoretical study of the thermoelectric-related transport properties of BilxSbx nanowires, and presents a theoretical framework for predicting the electrical properties of superlattice nanowires. A template-assisted fabrication scheme is employed to synthesize Bi-based nanowires by pressure injecting liquid metal alloys into the hexagonally packed cylindrical pores of anodic alumina. These nanowires possess a very high crystalline quality with a diameter-dependent crystallographic orientation along the wire axis. A theoretical model for Bil-Sbx nanowires is developed, taking into consideration the effects of cylindrical wire boundary, multiple and anisotropic carrier pockets, and non-parabolic dispersion relations. A unique semimetal-semiconductor (SM-SC) transition is predicted for these nanowires as the wire diameter decreases or as the Sb concentration increases. Also, an unusual physical phenomenon involving a very high hole density of states due to the coalescence of 10 hole carrier pockets, which is especially advantageous for improving the thermoelectric performance of p-type materials, is uncovered for BilxSbx nanowires. Various transport measurements are reported for Bi-related nanowire arrays as a function of temperature, wire diameter, Sb content, and magnetic field. R(T) measurements show distinct T dependences for semimetallic and semiconducting nanowires, as predicted by the theory, and the condition for the SM-SC transition can be clearly identified. Enhanced thermopower is observed for BilxSbx nanowires as the diameter decreases or as the Sb content increases, indicating that both quantum confinement effects and Sb alloying effects are important for improving the thermo-electric performance. (cont.) The theoretical model is further extended to study transport properties of Te-doped Bi nanowires and Sb nanowires, and good agreement between theoretical predictions and experimental results is obtained. A model for superlattice nanowires is presented to evaluate their potential for thermoelectric applications. Thermoelectric properties of superlattice nanowires made of various lead salts (PbS, PbSe, and PbTe) are investigated as a function of segment length, wire diameter, crystal orientation along the wire axis, and length ratio of the constituent nanodots. An interesting inversion of the potential barrier and well induced by quantum confinement is predicted in superlattice nanowires as the wire diameter decreases. ZT values higher than 4 and 6 are predicted for 5 nm-diameter PbSe/PbS and PbTe/PbSe superlattice nanowires, respectively, at 77K, and these ZT values are significantly larger than those of their corresponding alloy nanowires. For a given superlattice period, the ZT value can be further improved by adopting different segment lengths for the two constituent materials. The model developed here not only can determine the optimal superlattice nanowire parameters (segment length, diameter, materials, and doping level) for thermoelectric applications, but also can be extended to other superlattice systems, such as 3D quantum dot arrays ... by Yu-Ming Lin. Ph.D. 2005-06-02T16:18:55Z 2005-06-02T16:18:55Z 2003 2003 Thesis http://hdl.handle.net/1721.1/17593 53277729 eng M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission. http://dspace.mit.edu/handle/1721.1/7582 147 p. 6876723 bytes 6876531 bytes application/pdf application/pdf application/pdf Massachusetts Institute of Technology |
| spellingShingle | Electrical Engineering and Computer Science. Lin, Yu-Ming, 1974- Thermoelectric properties of Bi₁âx̳Sbx̳ nanowires and lead salt superlattice nanowires |
| title | Thermoelectric properties of Bi₁âx̳Sbx̳ nanowires and lead salt superlattice nanowires |
| title_full | Thermoelectric properties of Bi₁âx̳Sbx̳ nanowires and lead salt superlattice nanowires |
| title_fullStr | Thermoelectric properties of Bi₁âx̳Sbx̳ nanowires and lead salt superlattice nanowires |
| title_full_unstemmed | Thermoelectric properties of Bi₁âx̳Sbx̳ nanowires and lead salt superlattice nanowires |
| title_short | Thermoelectric properties of Bi₁âx̳Sbx̳ nanowires and lead salt superlattice nanowires |
| title_sort | thermoelectric properties of bi₁axi³sbxi³ nanowires and lead salt superlattice nanowires |
| topic | Electrical Engineering and Computer Science. |
| url | http://hdl.handle.net/1721.1/17593 |
| work_keys_str_mv | AT linyuming1974 thermoelectricpropertiesofbi1axi3sbxi3nanowiresandleadsaltsuperlatticenanowires |