Semiconductor Nanowires for Thermoelectrics Daniel Vakulov, R. Chavez, S. Gazibegović, R.W. van der Heijden, and E.P.A.M. Bakkers

Transcription

1 Semiconductor Nanowires for Thermoelectrics Daniel Vakulov, R. Chavez, S. Gazibegović, R.W. van der Heijden, and E.P.A.M. Bakkers Advanced Nanomaterials and Devices / Applied Physics department

2 Outline Motivation Semiconductor nanowires Measurements technique Thermal conductivity of InSb nanowires Conclusions and outlook 2

3 Outline Motivation Semiconductor nanowires Measurements technique Thermal conductivity of InSb nanowires Conclusions and outlook 3

4 Motivation 2/3 energy lost as heat Power generation 70% energy wasted as heat Car industry Heat dissipation * 4 *

5 Motivation 5

6 Motivation Conductivity Seebeck coefficient Heat TEGs Electrical energy ZT = σ S2 T κ e + κ L Temperature Thermal conductivity Efficiency up to ~ 12 % ( o C) J. Mater. Chem., 2011, 21,

7 Outline Motivation Semiconductor nanowires Measurements technique Thermal conductivity of InSb nanowires Conclusions and outlook 7

8 Semiconductor Nanowires ZT = σ S2 T κ L Appl. Phys. Lett. 87, (2005) Temperature dependence of ZT obtained by experiment for a Te-doped InSb bulk single crystal 300K Annu. Rev. Mater. Res : η = η C 1 + ZT ZT + T c /T h η C = T h T c T h ZT~3 η 41% 8 Appl. Phys. Lett., Vol. 84, No. 14, 2004

9 Semiconductor Nanowires Dificulties in increasing ZT in bulk materials: A limit to ZT is rapidly obtained in conventional materials So far, the best bulk materials have ZT~ 1 at 300K E.U. Rafailov (Editor) ISBN: Low-dimentional physics gives additional control: Enhanced density of states due to quantum confinement effect Increase S without reducing σ Boundary scattering at interfaces can reduce κ more than σ Possibility of materials engineering to futher improve ZT 9

10 Outline Motivation Semiconductor nanowires Measurements technique Thermal conductivity of InSb nanowires Conclusions and outlook 10

11 Measurements set-up Electrodes Pt/C contacts NanoWire PRT 1 um slope h = d T h dp h Nanotechnology, 26(38),

12 Measurements set-up Electrodes Pt/C contacts NanoWire PRT 1 um κ = G s 4L πd 2 slope h = d T h dp h where G s nanowire (NW) thermal conductance, L NW lenght, d NW diameter 12

13 Outline Motivation Semiconductor nanowires Measurements technique Thermal conductivity of InSb nanowires Conclusions and outlook 13

14 InSb Nanowires InSb NWs grows in <111> direction and has six {110} side facets Diameter of NWs does not change along the nanowire length InSb zinc blend single crystaline structure, Sb-polar binary InSb (no P or As incorporated) InSb {110} <111> Saša Gazibegović *TEM by Jordi Arbiol & Maria de la Mata, Institut de Ciència de Materials de Barcelona 14

15 InSb Nanowires 300K J. Appl. Phys. 43 (2010) Appl. Phys. Lett., Vol. 84, No. 14, 2004

16 Outline Motivation Semiconductor nanowires Measurements technique Thermal conductivity of InSb nanowires Conclusions and outlook 16

17 Conclusion and Outlook Semiconductor nanowires are very promising for thermoelectrics Low values of thermal conductivity of InSb nanowires were observed Surface scattering has to be considered Perform Seebeck coefficient and electrical conductivity measurements on InSb nanowires Thin InSb nanowires are good candidates for thermoelectric application 17

18 Thank you for your attention! 18