1. Piezoelectric metal oxide nanostructures for energy harvesting Reza Saberi Moghaddam

2. Outline  Energy harvesting  Piezoelectric effect  Type of material in self powering system  Best candidates of nanostructures Mechanical properties  Best choice for self-powering nanosystem Electrical properties  Results  Conclusions 2 "Energy & Nano" - Top Master in Nanoscience Symposium 17 June 2009

3. Energy harvesting  Definition: Capturing and storing energy from available sources in environment which are currently wasting.  Applications: In small and wireless autonomous devices (wearable electronics)  Types: 1- Photo/electrical energy harvesting 2- Thermal/electrical energy harvesting 3- Mechanical/electrical energy harvesting 3 "Energy & Nano" - Top Master in Nanoscience Symposium 17 June 2009

4. Energy harvesting Photo/electrical energy harvesting  Photovoltaic energy harvesting Thermal/electrical energy harvesting  Pyroelectric energy harvesting 4 http://dev.nsta.org/evwebs/3368/images/solar_cells_panels_array_monocrystaline.jpg J. Xie, P. P. Mane, C. W. Green, K. M. Mossi, K. K. Leang, Proc of SMASIS08, October 28-30, 2008, Maryland, USA "Energy & Nano" - Top Master in Nanoscience Symposium 17 June 2009

5. Energy harvesting 5 M. Miyazaki,H.Tanaka,G.Ono,T.Nagano,N.Ohkubo,T.Kawahara,K.Yano, Proceedings of the 2003 international symposium on Low power electronics and design, Seoul, Korea,(2003),193 Biomechanical based energy harvesting Electrostatic (capacitive) based energy harvesting Mechanical/electrical energy harvesting "Energy & Nano" - Top Master in Nanoscience Symposium 17 June 2009

6. Energy harvesting 6 X. Wang,J. Song, J. Liu, Z.L. Wang, SCIEN CE,316 (2007 ) 102 R. Amirtharajah, A.P. Chandrakasan, " IEEE Journal of Solid-State Circuits, vol. 33, n. 5, pp. 687-695, 1998 Electromagnetic based energy harvesting Piezoelectric based energy harvesting Mechanical/electrical energy harvesting "Energy & Nano" - Top Master in Nanoscience Symposium 17 June 2009

7. Piezoelectric effect Direct piezoelectric effect: Conversion of mechanical stress to electrical potential Reverse piezoelectric effect: Conversion of electrical voltage to mechanical motion 7 http://www.keramverband.de/keramik/englisch/fachinfo/eigenschaften/eigenschaften_piezo.htm "Energy & Nano" - Top Master in Nanoscience Symposium 17 June 2009 P m = d mij X ij x ij = d mij E m

8. Piezoelectric materials Insulator:  Barium Sodium Niobate  Lithium Niobate  Lead Zirconate Titanate  Quarts Semiconductor:  Cadmium Sulfide  Gallium Arsenide  Aluminum nitride (AIN)  Polyvinylidene fluoride (PVDF)  Zinc Sulfide "Energy & Nano" - Top Master in Nanoscience Symposium 17 June 2009

9. Piezoelectric Materials  Cadmium Sulfide (d 33 = 10.3 pm/V)  Gallium Arsenide (d 14 = 2.6 pm/V)  Tellurium Dioxide (d 14 = 8.13 pm/V)  Aluminum nitride (AIN) (d 33 = 5.2 pm/V)  Zinc Sulfide (d 33 = 3.23 pm/V)  Zinc Oxide ( d 33 = 11.67 pm/V ) "Energy & Nano" - Top Master in Nanoscience Symposium 17 June 2009

10. Type of Materials  ZnO as a piezoelectric energy harvesting material: Lack of inversion center in wurtzite structure → strong piezoelectricity Large electromechanical coupling Semiconducting behaviour More resistance to radiation Biosafe with low toxicity (medical applications) Large diversity of nanostructures 10 R. L. Johnson, Master Thesis, Iowa State University 2005 "Energy & Nano" - Top Master in Nanoscience Symposium 17 June 2009

11. Zinc Oxide Nanostructures  Nanorods Nanobelts Hierarchical nanostructures  Nanocombs Nanosprings Nanorings 11 Z. L. Wang, Materialstoday(2004)26 "Energy & Nano" - Top Master in Nanoscience Symposium 17 June 2009

12. ZnO nanostructure for energy harvesting Nanobelts /nanowires  One dimensional structure  Large elastic deformation without plastic deformation or fracture  Free of dislocations because of their small diameter  Bent under extremely small applied force.  Nanowire Nanobelt 12 Z. L. Wang, Materialstoday(2004)26 "Energy & Nano" - Top Master in Nanoscience Symposium 17 June 2009

13. Mechanical properties of ZnO NW  Using AFM technique  Recording of topography and lateral force image by AFM contact mode  Determination of elestic modulus of individual NW: 13 X. Wang, J. Song, Z. L. Wang, J. Mater. Chem., 2007, 17, 711–720 "Energy & Nano" - Top Master in Nanoscience Symposium 17 June 2009

14. Mechanical properties of ZnO NB  Using TEM technique  Sample holder for TEM to apply voltage across NB  Induced mechanical resonance for applied frequency near natural frequency of NB 14 Z.L. Wang/ Materials Science and Engineering R 64 (2009) 33–71 "Energy & Nano" - Top Master in Nanoscience Symposium 17 June 2009

15. Mechanical Modulus of ZnO NB/NW/Crystal  Elastic modulus of individual NW :  Elastic modulus of individual NB :  Elastic modulus of ZnO crystal : 15 "Energy & Nano" - Top Master in Nanoscience Symposium 17 June 2009

16. Preference of Nanowires versus Nanobelts  Lower range of Young modulus  Higher sensitivity to mechanical stress  More directionality  Easy to grow via chemical synthesis on any shaped substrate made of any material 16 "Energy & Nano" - Top Master in Nanoscience Symposium 17 June 2009

17. Electrical processes in Nanowires (NW)  Coupling of piezoelectric and semiconducting properties of ZnO nanowires: 1-Piezoelectric properties:  Charge Creation under mechanical stress 2-Semiconducting properties:  Low enough conductivity and carrier density for preserving the piezoelectric potential distribution in the NWs  High enough to transport the current under the driving of the piezoelectric potential energy 17 "Energy & Nano" - Top Master in Nanoscience Symposium 17 June 2009

18. Electrical processes in Nanowires (NW)  Creation of strain field with NW  Stretching of outer surface of NW ( positive strain)  Compression of inner surface (negative strain)  Formation of electric field along the NW in z direction ( )  ZnO NW acts as shottky diode (forward and reverse biased) 18 Z. L. Wang, J. Song, SCIENCE, 312 (2006) 242 "Energy & Nano" - Top Master in Nanoscience Symposium 17 June 2009

19. Electrical processes in Nanowires (NW) 19 J. Liu, P. Fei, J. H. Song, X. D. Wang, C. S. Lao, R. Tummala, Z. L. Wang, Nano Lett. 2008, 8, 328 "Energy & Nano" - Top Master in Nanoscience Symposium 17 June 2009 Active NG (ZnO NWs as a Schottky diode) Defective NG (ZnO NWs as a ohmic resistance)

20. Results  AFM using Si tip coated with Pt  Using normal force in contact mode 20 Z. L. Wang, J. Song, SCIENCE, 312 (2006) 242 "Energy & Nano" - Top Master in Nanoscience Symposium 17 June 2009

21. Results  Demonstration of ultra-sonic wave transformation to electricity 21 X. Wang,J. Song, J. Liu, Z.L. Wang, SCIEN CE,316 (2007 ) 102 "Energy & Nano" - Top Master in Nanoscience Symposium 17 June 2009

22. Conclusions  Importance of harvesting energy from available sources in environment.  Using of self-powering systems without changing battery  Enhancement of harvesting efficiency in nanosystems  Using ZnO as a suitable material for self-powering nanosystems  Coupled semiconducting-piezoelectric properties of ZnO nanostructure  Nanowires /nanobelts are best candidate because of one- dimensional & low Young Modulus and free of dislocation  More alignment and lower Young modulus of NWs made it best choice 22 "Energy & Nano" - Top Master in Nanoscience Symposium 17 June 2009

23. I would like to acknowledge Prof. B. Noheda for helping me to prepare this presentation. 23 "Energy & Nano" - Top Master in Nanoscience Symposium 17 June 2009

24. Thank you for your attention Questions ? 24 "Energy & Nano" - Top Master in Nanoscience Symposium 17 June 2009