傳統熱電塊材經常應用在大尺度的熱管理，而薄膜型熱電材料則常應用在微電子學中小尺度的熱管理。碲化鉍系化合物因其有在室溫下高熱電優質(ZT)的優點，許多研究以此化合物作為基礎來開發高效率的熱電材料。先前的研究已經證明電流輔助熱退火處理能夠改善碲化鉍系薄膜的熱電性質。然而此種薄膜材料的熱性質卻未被完全了解。
本研究延伸了傳統的 3omega量測技術，並發展出一套考慮介面熱阻效應的方法來量測平行於膜面的熱傳導係數。我們藉由量測二氧化矽薄膜來驗證此方法的可行性，爾後用此方法來量測熱電薄膜的平行膜面熱傳導係數。本研究使用濺鍍法沉積 p 型 Bio.5Sb1.5Te3 薄膜在含有氧化層的矽基板上。在熱退火過程中，我們施加一個密度為2500A/cm2 的電流到熱電薄膜，並將溫度控制在 300◦C。相對於單純熱退火試片，電流輔助退火試片擁有較高的 Seebeck 係數與載子遷移率，以及較低的載子濃度。此外，電流輔助退火試片的平行 kx 與垂直膜面 ky 的熱傳導係數都比熱退火試片的還要高。本研究發現電流輔助退火試片呈現出一個熱傳導的高非均向性，且此非均向比例值 kx/ky 為 1.8。根據微結構與熱電性質分析，此非均向性主要由 (00l) 晶面成長所貢獻，而其他因素則對此結果影響不大。

As traditional bulk thermoelectric (TE) materials are usually applied to large-scale heat management, thin film thermoelectric materials are often used to manage small-scale heat in the field of microelectronics. Bismuth telluride based compound materials are well-known for its high ZT value at room temperature regime. Previous studies have shown that a current-assisted thermal annealing was able to improve thermoelectric properties of Bi-Te based thin films. Yet, the thermal conductivity of such thin film materials is not fully investigated.
In this research, we extended the conventional 3omega technique and developed a method, which considers the interfacial thermal resistance, to measure the in-plane thermal conductivity of thermoelectric thin films. Silicon dioxide thin films were used to verify the feasibility of our method, and subsequently, we measured the in-plane thermal conductivity of TE thin films. P-type Bio.5Sb1.5Te3 thin films were deposited by sputtering on a thermally oxidized silicon substrate. A current-assisted thermal annealing is applied to the thin films at a current density of 2500A/cm2 when annealed at 300 ◦C. The electrically stressed Bio.5Sb1.5Te3 thin films have higher Seebeck coefficient, higher mobility and lower carrier concentration than the thermally annealed films. In addition, both cross-plane (ky) and in-plane (kx) thermal conductivities of the electrically stressed TE films were found to be larger than those of the thermally annealed films. The electrically stressed films shows a high anisotropy in thermal conductivity with a ratio kx/ky equal to 1.8. According to the microstructural and thermoelectric analysis, the measured anisotropy is mostly attributed to the development of (00l) film texture, as other factors show little impact on such results.

Chapter 1 Introduction 1
1.1 Preface . . .1
1.2 Thermoelectric effect and devices. . .1
1.3 Motivation . . .4
Chapter 2 Literature review 6
2.1 Bi-Sb-Te based thermoelectric materials . . .6
2.2 Current-assisted thermal treatment . . .8
2.3 Thermal conductivity measurement . . .11
2.3.1 Cross-plane thermal conductivity measurement. . .12
2.3.2 In-plane thermal conductivity measurement. . .15
Chapter 3 Experimental method 19
3.1 Sample preparation . . .19
3.2 Analysis of thermoelectric properties . . .23
3.2.1 Seebeck measurement . . .23
3.2.2 Hall measurement. . .23
3.2.3 3ω measurement. . .24
3.2.4 Microstructure analysis. . .33
Chapter 4 Results and discussion 34
4.1 Verification of fitting model . . .34
4.1.1 Fitting algorithm. . .34
4.1.2 3ω measurement. . .37
4.2 Characterization of Bi-Sb-Te films . . .42
4.2.1 3ω measurement . . .43
4.2.2 Uncertainty analysis of measuring anisotropy. . .46
4.2.3 Differentiation of electronic and phonon contributions to thermal transport properties. . .48
4.2.4 Microstructural characterization . . . 49
4.3 Overall discussion . . .52
Chapter 5 Conclusion 57
References 61

[1]C. B. Vining. Nature 413, 577 (2001).
[2]H. J. Goldsmid. in CRC Handbook of Thermoelectrics. CRC Press, (1995). edited by D. M. Rowe.
[3]G. S. Nolas, J. Sharp, H. J. Goldsmid. Thermoelectrics Basic Principles and New Materials Developments, volume 45. Springer Berlin Heidelberg, (2001).
[4]G. J. Snyder, E. S. Toberer. Nature Materials 7, 105 (2008).
[5]K. M. Liou, C. N. Liao. J. Appl. Phys. 108, 053711 (2010).
[6]蘇小維. 電流輔助熱退火處理對 Bio.5Sb1.5Te3 濺鍍薄膜熱電傳輸性質研究國立清華大學碩士論文 (2010).
[7]W .M. Yim, F. D. Rosi. Solid-State Electronics 15, 1121 (1972).
[8]F .D. Rosi, B. Abeles, R. V. Jensen. J. Phys. Chem. Solids 10, 191 (1959).
[9]U .Birkholz. Z. Naturforschung A 13, 780 (1958).
[10]D. M. Rowe. CRC Handbook of Thermoelectrics. CRC Press, (1995). p.212.
[11]G. Wang, T. Cagin. Phys. Rev. B 76, 075201 (2007).
[12]G. R. Miller, Che-Yu Li. J. Phys. Chem. Solids 26, 173 (1965).
[13]J. Horák, K. Čermák, L. Koudelka. J. Phys. Chem. Solids 47, 805 (1986).
[14]https://en.wikipedia.org/wiki/Electronegativity.
[15]A. Hashibon, C. Elsässer. Phys. Rev. B 84, 144117 (2011).
[16]C. Lahalle-Gravier, B. Lenoir, H. Scherrer, S. Scherrer. J. Phys. Chem. Solids 59, 13 (1998).
[17]T. Caillat, M. Carle, P. Pierrat, H. Scherrer, S. Scherrer. J. Phys. Chem. Solids 53, 1121 (1992).
[18]L. P. Bulat, I. A. Drabkin, V. V. Karataev, V. B. Osvenskiĭ, D. A. Pshenaĭ-
Severin. Physics of the Solid State 52, 1836 (2010).
[19]J. Jiang, L. Chen, S. Bai, Q. Yao. Journal of Alloys and Compounds 390, 208
(2005).
[20]T. Y. Yang, I. M. Park, B. J. Kim, Y. C. Joo. Appl. Phys. Lett. 95, 032104
(2009).
[21]A. T. Wu, K. N. Tu, J. R. Lloyd, N. Tamura, B. C. Valek, C. R. Kao. Appl. Phys. Lett. 85, 2490 (2004).
[22]A. T. Wu, A. M. Gusak, K. N. Tu, C. R. Kao. Appl. Phys. Lett. 86, 2491902
(2005).
[23]D. Moldovan, V. Yamakov, D. Wolf, S. R. Phillpot. Phys. Rev. Lett. 89,
206101 (2002).
[24]H. Chen, C. Hang, X. Fu, M. Li. J. Electron. Mater. 44 (2015).
[25]T. Yao. Appl. Phys. Lett 51, 1798 (1987).
[26]J. A. Malen, K. Baheti, T. Tong, Y. Zhao, J. A. Hudgings, A. Majumdar. J. Heat Transfer 133, 081601 (2011).
[27]D. G. Cahill. Rev. Sci. Instrum 61, 802 (1990).
[28]T. Borca-Tasciuc, A. R. Kumar, G. Chen. Rev. Sci. Instrum 72, 2139 (2001).
[29]H. C. Chien, D. J. Yao, M. J. Huang, T. Y. Chang. Rev. Sci. Instrum. 79, 054902 (2008).
[30]A. Mavrokefalos, M. T. Pettes, F. Zhou, L. Shi. Rev. Sci. Instrum 78, 034901 (2007).
[31]C. Dames. Measuring The Thermal Conductivity of Thin Films: 3 Omega and Related Electrothermal Methods. in Annual Rev Heat Transfer, (2013). p.7-49.
[32]G. Chen, S. Q. Zhou, D.-Y. Yao, C. J. Kim, X. Y. Zheng, Z. L. Liu, K.L. Wang. Proceedings of the 17th International Conference Thermoelectrics, Nagoya, Japan , 202 (1998).
[33]J. H. Kim, A. Feldman, D. Novotny. J. Appl. Phys. 86 (1999).
[34]J. L. Liu, A. Khitun, K. L. Wang, T. Borca-Tasciuc, W. L. Liu, G. Chen, D. P. Yu. J. Crystal Growth 227, 1111 (2001).
[35]W. L. Liu, T. Borca-Tasciuc, G. Chen, J. L. Liu, K. L. Wang. J. Nanosci. Nanotechnol 1, 39 (2001).
[36]D. -A. Borca-Tasciuc, G. Chen. J. Appl. Phys. 97, 084303 (2005).
[37]D. R. Dunbobbin, J. Faguet. Proc. SPIE, Optical/Laser Microlithography 922 (1988).
[38]S. M. Lee, D. G. Cahill. J. Appl. Phys 81, 2590 (1997).
[39]王昱筑. 以 3ω 法量測 Bio.5Sb1.5Te3 薄膜之熱傳導係數國立清華大學碩士論文 (2008).
[40]H. R. Shanks, P. D. Maycock, P. H. Sidles, G. C. Danielson. Phys. Rev. 130, 1743 (1963).
[41]R. Venkatasubramanian, E. Siivola, T. Colpitts, B. O’Quinn. Nature 413, 597 (2001).
[42]H. J. Goldsmid. Proc. Phys. Soc B 69, 203 (1956).
[43]D. M. Rowe. Thermoelectrics Handbook: Macro to Nano. CRC press, (2006). chapter 27.
[44]D. M. Rowe. Thermoelectrics Handbook: Macro to Nano. CRC press, (2006). chapter 9.