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Thermoelectric and thermal rectification properties of quantum dot junctions

Thermoelectric and thermal rectification properties of quantum dot junctions. David M T Kuo 1 and Yia-Chung Chang 2 1:Department of Electrical Engineering, National Central University, Taiwan 2:Research Center for Applied Science, Academic Sinica, Taiwan.

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Thermoelectric and thermal rectification properties of quantum dot junctions

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  1. Thermoelectric and thermal rectification properties of quantum dot junctions David M T Kuo1 and Yia-Chung Chang2 1:Department of Electrical Engineering, National Central University, Taiwan 2:Research Center for Applied Science, Academic Sinica, Taiwan The detail can be found in PRB 81, 205321 (2010)

  2. Urbana-2003-July

  3. References • [1]A. J. Minnich, M. S. Dresselhaus, Z. F. Ren and G. Chen, Energy Environ Science, 2, 466 (2009) • [2]G. Mahan, B. Sales and J. Sharp, Physics Today,50, 42 (1997). • [3]R. Venkatasubramanian, E. Siivola,T. Colpitts,B. O'Quinn, Nature 413,597 (2001).”BiTe/SbTe quantum well superlattice” • [4]A. I. Boukai, Y. Bunimovich, J. Tahir-Kheli, J. K.Yu, W. A. Goddard III and J. R. Heath, Nature, 451, 168(2008).”Silicon quantum wire” • [5]T. C. Harman, P. J. Taylor, M. P. Walsh, B. E.LaForge, Science 297, 2229 (2002).”PbSeTe Quantum dot superlattice “ • [6]K. F. Hsu,S. Loo,F. Guo,W. Chen,J. S. Dyck,C. Uher, T. Hogan,E. K. Polychroniadis,M. G. Kanatzidis, Science 303, 818(2004) • .[7]A. Majumdar, Science 303, 777 (2004). • [8]G. Chen, M. S. Dresselhaus, G. Dresselhaus, J. P.Fleurial and T. Caillat, International Materials Reviews,48, 45 (2003) • [9]Y. M. Lin and M. S. Dresselhaus, Phys. Rev. B 68, 075304 (2003).

  4. 1:System Amorphous insulator Large intradot and interdot Coulomb interactions

  5. 1-0:Fabrication

  6. 1-1:Hamiltonian (Anderson model) The key effects included are the intradot and interdot Coulomb interactions and the coupling between the QDs with the metallic leads There is one energy level within each QD

  7. 1-2:Nonequilibrium Green’s function technique Ref[1]D. M. T. Kuo and Y. C. Chang, Phys. Rev. Lett. 99,086803(2007) Ref[2]Y. C. Chang and D. M. T Kuo, Phys. Rev. B 77,245412 (2008)

  8. 2:Linear response Homogenous QD size, dilute QD density Eg EF ZT as a function of T for different detuning energies. Solid and dash lines correspond, respectively, without and with intradot Coulomb interactions . Ref[3]P. Murphy, S. Mukerjee, J. Morre, Phys. Rev. B 78, 161406 (2008).

  9. 2-1:Interdot Coulomb interactions High QD density Side view (a) (b) (c ) (d) (c) (a) (b) (d) Top view

  10. 2-2: ZT detuned by Eg Noninteraction case High QD density Eg EF

  11. 2-3: Inelastic scattering effect on ZT QD size fluctuations, defects between metallic electrodes and insulators and electron-phonon interactions,

  12. 2-4: Electrical conductance, thermal power and thermal conductance These curves correspond to Fig.3. The temperature-dependence of ZT is similar to that of the electrical conductivity.

  13. 2-5: Ge, S and Ke as a function of gate voltage Ge: Coulomb oscillation S: Sawtooth-like shape Ke: Sensitive to T

  14. 2-6:Midway between the good and poor conductors

  15. 2.7 Without vacuum layer

  16. 2.8 Different dot sizes 2nm

  17. 2.9 Thickness of SiO2

  18. 3-1:Thermal rectification effect Two dot case TL TR TL TR

  19. 3-2: Thermal rectification efficiency(2 dots) TL TR TR TL Ref[4] R. Scheiber et al, New. J. Phys. 10, 083016 (2008)

  20. 3-3: Thermal rectification (three QDs) Dot A

  21. 3-4:The shift of QD energy levels caused by electrochemical potential Solid curves including Dashed curves excluding TH TL TL TH VH VL VL VH

  22. 3-5: Interdot Coulomb interactions Solid line UAC=15kBT0 Dashed line UAC=10kBT0 Dotted line UAC=5kBT0 Dot-Dashed line UAC=0

  23. 3-6: Thermal rectification efficiency 3 dots 2 dots

  24. 4:Conclusion (A) Figure of merit, ZT [1]The optimization of ZT depends not only on the temperature but also on the detuning energy [2]Inelastic scattering effect of electron-phonon interactions, QD size fluctuations, and defects lead to a considerable reduction to the ZT values (B)Thermal rectification [1] Very strong asymmetrical coupling between the dots and the electrodes. [2] Large energy level separation between dots [3]Strong interdot Coulomb interactions

  25. 4. Thermal rectification

  26. 4.1 Tunneling rates TL TH TH TL

  27. 4.2 Tuning energy level

  28. 4.3 Three-dots with uniform size The dot-dashed line indicates the junction system without asymmetrical heat current, when dots are identical.

  29. 4.4: Different sizes

  30. 4.5 :Gate voltage

  31. 4.6: Interdot Coulomb interactions

  32. 4.7:Energy level shifted by electrochemical potential

  33. 5:A single molecular QD (a)Hard to scaling up the thermal devices. (b)Hard to integrate with silicon based electronics. [1]P. Murphy, S.Mukerjee and J. Morre, Phys. Rev. B 78, 161406 (2008).

  34. 5.1:

  35. 5.2:Detuning energy

  36. 5.3:

  37. 5.4

  38. 5.5

  39. 5.6:

  40. 5.7: S to resolve high order phonon assisted tunneling

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