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Self-Assembled Metallic Nanostructures as Electronic Devices

Self-Assembled Metallic Nanostructures as Electronic Devices. Andrew van Bommel (as George M. Whitesides) March 30 th , 2006. Me. Harvard #1 ISI ranked chemist 900 pubs by 2005 70 papers with more than 100 citations “ To be able to make complex systems…by self-assembly ”

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Self-Assembled Metallic Nanostructures as Electronic Devices

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  1. Self-Assembled Metallic Nanostructures as Electronic Devices Andrew van Bommel (as George M. Whitesides) March 30th, 2006

  2. Me • Harvard • #1 ISI ranked chemist • 900 pubs by 2005 • 70 papers with more than 100 citations • “To be able to make complex systems…by self-assembly” -The Holy Grail of nanotech, according to me • “A word, not a field” -Me on nanotechnology

  3. Summary • Previous Work I. 3D self-assembled electronic devices II. Self-assembled nanostructures i. Metallic polyhedra ii. Free-standing metallic pyramidal shells iii. Metallic half-shells iv. Self-assembly of nanorods • Future work • Self-assembled patterned metallic polyhedra • Magnetically assembled metallic nanopyramids • Self-assembled nanotetrahedra

  4. I. 3D Self-assembled E-devices • 3D networks are found in current devices • Formation by stacking parallel planes • Our work: • Demonstrates the formation of parallel and serial networks by self-assembly • LEDs attached to demonstrate electrical conductivity • Self-assembly by minimization of interfacial free energy between drops of solder on stacked polyhedra  dot-on-dot electrical conductivity

  5. The elements were removed from the copper/polyimide sheet. Pattern glued onto the faces of the truncated octahedron. LEDs soldered onto the contact pads The patterns were covered with solder, self-assembly occurred in hot aqueous KBr solution Copper dots, contact pads, and wires were formed on a copper-polyimide sheet using photolithography and etching. I. 3D Self-assembled E-devices Gracias et al., Science, 289 (2000) 1170.

  6. The pattern of copper dots, wires, and contact pads. A patterned TO with 3 LEDs before self-assembly. A self-assembled aggregate of patterned TOs. LEDs, connected by serial loops, are powered by pairs of leads. I. 3D Self-assembled E-devices

  7. II. i. S-Aed Metallic Polyhedra • Gracias et al., Adv. Mater., 14 (2002) 235. • Polyhedra formed by auto-folding: • 2D pattern formed • Add solder • Spontaneous folding occurs by heating: under the influence of the surface tension of the liquid solder • Polyhedra with varied amount of faces can form, depending of the patterning

  8. TOP VIEW II. i. S-Aed Metallic Polyhedra Sacrificial layer of SiO2 is deposited on Si substrate (thermal growth).

  9. hn II. i. S-Aed Metallic Polyhedra Photolithography removes selected portions of sacrificial layer.

  10. TOP VIEW II. i. S-Aed Metallic Polyhedra Metal (Cr/Au) is deposited by evaporation to make the wafer electrically conductive for electrodeposition.

  11. hn II. i. S-Aed Metallic Polyhedra Photolithography removes more sacrificial layer.

  12. TOP VIEW II. i. S-Aed Metallic Polyhedra Further metallization.

  13. TOP VIEW II. i. S-Aed Metallic Polyhedra Electrodeposition of nickel to build up polyhedron faces

  14. II. i. S-Aed Metallic Polyhedra Solder (Bi alloy) deposition (by solder dip-coating).

  15. TOP VIEW II. i. S-Aed Metallic Polyhedra Dissolution of Si in KOH.

  16. 100-300 mm 300-500 nm thick walls Heat to induce folding of the structure. Heating Dissolution of SiO2 in HF.

  17. II. i. S-Aed Metallic Polyhedra

  18. II. i. S-Aed Metallic Polyhedra

  19. Ti/Pd PR II. ii. Metallic Pyramidal Shells Xu et al., Nano Lett., 4 (2004) 2509. SiO2 Si Sonication in acetone to remove photoresist. Selection of SiO2 etched with reactive ion etch. Si etched with KOH/i-PrOH. Ti/Pd layer coated on substrate (e-beam vapor deposition). Photoresist laid on silica/silicon substrate.

  20. Ti/Pd II. ii. Metallic Pyramidal Shells SiO2 Si Thiols stamped on Ti/Pd/SiO2/Si substrate. Ti/Pd etched (Fe-based etchant). SiO2/Si etched with KOH.

  21. Ni Ti/Pd Au epoxy II. ii. Metallic Pyramidal Shells SiO2 Si Ti/Pd etched in aqua regia solution. Gold deposited to allow for uniform electrodeposition. Epoxy layer deposited. Ni layer electrodeposited.

  22. Ni Au epoxy II. ii. Metallic Pyramidal Shells Au and epoxy layer peeled off. Si substrate etched with KOH.

  23. II. ii. Metallic Pyramidal Shells

  24. Au II. iii. Metallic Half-Shells Love et al., Nano Lett., 2 (2002) 891. Evaporation of gold onto silica nanospheres. Si SiO2

  25. II. iii. Metallic Half-Shells • Beads removed from Si template by sonication • Silica template dissolved in HF • Metallic half-spheres: • Au (450 nm, 10 nm thick) • Pd (290 nm, 10 nm thick) • Pd (100 nm, 8 nm thick) • Au (100 nm, 8 nm thick)

  26. II. iii. Metallic Half-Shells • Template-assisted self-assembly: • Shells deposited into arrays of microwells defined in a film of photoresist • 2 mm aggregates of gold half shells (with 290 nm diameter)

  27. II. iv. Self-Assembly of Nanorods Martin et al., Adv. Mater., 11 (1999) 1021). Au electroplated in pores Further Electroplating… Ni electroplated on Al Ag film evaporated on Alumina membrane Ag electroplated on Ag film Alumina dissolved in NaOH Ag dissolved in HNO3

  28. II. iv. Self-Assembly of Nanorods Love et al. , J. Am. Chem. Soc., 125 (2003) 12696. • Magnetize • Sononicate 3. Self-assemble • The nickel sections of the rods were magnetized. • Sonication yielded a suspension of rods. • Self-assembly occurred in suspension of rods, which were deposited on a silicon wafer for imaging.

  29. II. iv. Self-Assembly of Nanorods Nanobundles included 10-100 nanorods. Au sections = 600 nm, Ni sections = 200 nm.

  30. Summary • Self-assembly can lead to: • Polyhedra as electronic structures • Nano abrication and self-assembly forms: • Metallic polyhedra, pyramidal shells, half shells, and rods • Self-assembly can be carried out by: • Adding solder to the 2D pattern • Template-assisted self-assembly • Magnetization

  31. Nanotech Potential

  32. Future Work Outline • Form nanoelectronic devices through several methods: • Application of auto-folding of polyhedra • Application of magnetism of magnetic particles • In General: Or form micro/nano polyhedra with one of techniques previously discussed - patterning adds electronic functionality. Self-assemble polyhedra using magnetism (if required). Allow for self-assembly of functionalized nanopolyhedra.

  33. Pattern of Ti/Pd on SiO2 can be laid down though photolithography, etching, and metal deposition (recall: metal deposition of pyramidal shells): serves as the negative 1. Patterning of Nanopolyhedra Cu can be deposited and template removed, leaving Cu electronic array in two dimensions Metallization will occur after these steps (as before) since circuiting has to be on the outside of the polyhedron.

  34. 1. Patterning of Nanopolyhedra Through the proper choice of solder added to the copper electrical networks, self-assembly will occur:

  35. Ni Au 2. Pyramidal Shells • Metallic Pyramidal Shells • Instead, deposit Ni/Au in sequence: Ni Add Cu circuitry via photolithography, metal deposition Fill with Au

  36. 2. Pyramidal Shells • Magnetization can orient the nanocircuits:

  37. 3. Self-Assembled Nanotetrahedra Deposition of metal by evaporation can form nanotetrahedra on metallic half-spheres. (Haynes et al., J. Phys. Chem. B. 105 (2001) 5599.

  38. 3. Self-Assembled Nanotetrahedra • Template-assisted self-assembly: • Tetrahedra instead of spheres described earlier • Lithographic techniques can apply wiring to the polyhedra: electronic applications

  39. Summary • Past work has shown that we have had success with self-assembly of electronic devices and self-assembly/fabrication of micro and nanopolyhedra • Future work will focus on the application of bulk and micro/nano self-assembly to nanomaterials in the formation of electronic devices • Patterning of electrical networks on micropolyhedra, pyramidal shells, and nano half-shells

  40. References D. H. Gracias, J. Tien, T. L. Breen, C. Hsu, and G. M. Whitesides. Forming Electrical Networks in Three Dimensions by Self-Assembly. Science. 289 (2000) 1170. D. H. Gracias, V. Kavthekar, J. C. Love, K. E. Paul, and G. M. Whitesides. Fabrication of Micrometer-Scale, Patterned polyhedra by Self-Assembly. Adv. Mater. 14 (2002) 235. Q. Xu, I. tonks, M. J. Fuerstman, J. C. Love, and G. M. Whitesides. Fabrication of Free-Standing Metallic Pyramidal Shells. Nano Lett. 4 (2004) 2509. J. C. Love, B. D. Gates, D. B. Wolfe, K. E. Paul, and G. M. Whitesides. Fabrication and Wetting properties of Metallic Half-Shells with Submicron Diameters. Nano Lett. 2 (2002) 891. J. C. Love, A. R. Urach, M. G. Prentiss, and G. M. Whitesides. Three-Dimensional Self-Assembly of Metallic Rods with Submicron Diameters Using Magnetic Interactions. J. Am. Chem. Soc. 125 (2003) 12696. B. R. Martin, D. J. Dermody, B. D. Reiss, M. Fang, L. A. Lyon, M. J. Natan, and T. E. Mallouk. Orthogonal Self-Asssembly on Colloidal Gold-Platinum Nanorods. Adv. Mater. 11 (1999) 1021.

  41. Acknowledgements

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