Nanotechnology – technology in everything


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Nanotechnology – technology in everything

Gehan Amaratunga
Engineering Dept.
Cambridge University

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  • Nano means less than 100 nm
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  • Nanotechnology – technology in everything

    1. 1. Nanotechnology – technology in everything Gehan Amaratunga Engineering Dept. Cambridge University
    2. 2. The scale of the physical world
    3. 3. Contact CE NANO NANO
    4. 4. Nanotechnology today <ul><li>will generate $4 trillion by Lux Research (2008) estimates that: </li></ul><ul><ul><li>nanotechnology was incorporated in: </li></ul></ul><ul><ul><ul><li>$1.1 trillion worth of products in 2007 and </li></ul></ul></ul><ul><ul><ul><li>$3.1 trillion in 2008 </li></ul></ul></ul><ul><ul><li>$1 trillion of 2007 nanotechnology product revenue was generated by advances in existing semiconductor process techniques </li></ul></ul><ul><ul><ul><li>Advances to 90 nm, 65 nm nodes </li></ul></ul></ul><ul><ul><li>Nanotechnology products 2015 ! </li></ul></ul>
    5. 5. What does the 50 nm node in electronic devices mean? <ul><li>Man made electronics are approaching the size of biological organisms </li></ul>Transistor for 90 nm node (Source: Intel) Influenza virus (Source: CDC)
    6. 6. Integrated Circuit Advances <ul><li>Continued progress to 90 nm, 65 & 45 nm nodes has brought semiconductor manufacture into the world of nanotechnology </li></ul><ul><ul><li>Moore’s law dictates we must halve the size of a transistor every 24 months </li></ul></ul><ul><ul><ul><li>This means reducing smallest dimension by factor of 0.7 </li></ul></ul></ul><ul><ul><ul><li>Some existing components (dielectric) have already reached their limits </li></ul></ul></ul><ul><ul><li>Continuation of Moore’s law requires real progress in alternative nanotechnology materials, structures and devices </li></ul></ul>
    7. 7. Nanotechnology – consumer products today <ul><li>Appliances </li></ul><ul><ul><li>Batteries </li></ul></ul><ul><ul><li>Heating, Cooling and Air </li></ul></ul><ul><ul><li>Large Kitchen Appliances </li></ul></ul><ul><ul><li>Laundry & Clothing Care </li></ul></ul><ul><li>Automotive </li></ul><ul><li>Coatings </li></ul><ul><li>Electronics and Computers </li></ul><ul><ul><li>Audio , Television, Cameras </li></ul></ul><ul><ul><li>Computer Hardware , displays </li></ul></ul><ul><ul><li>Mobile Devices and Communications </li></ul></ul><ul><li>Food and Beverage </li></ul><ul><ul><li>Cooking </li></ul></ul><ul><ul><li>Storage </li></ul></ul><ul><li>Goods for Children </li></ul><ul><ul><li>Toys and Games </li></ul></ul><ul><li>Health and Fitness </li></ul><ul><ul><li>Clothing, Sporting Goods </li></ul></ul><ul><ul><li>Sunscreen </li></ul></ul><ul><ul><li>Cosmetics, Personal Care </li></ul></ul><ul><ul><li>Filtration </li></ul></ul><ul><li>Home and Garden </li></ul><ul><ul><li>Cleaning </li></ul></ul><ul><ul><li>Construction Materials </li></ul></ul><ul><ul><li>Home Furnishings </li></ul></ul><ul><ul><li>Luggage </li></ul></ul><ul><ul><li>Luxury </li></ul></ul><ul><ul><li>Paint </li></ul></ul>
    8. 8. Nanotechnology – some examples Photo by David Hawxhurst-Woodrow Wilson International Center for Scholars
    9. 9. Nanotechnology products - today <ul><li>Nanotechnology consumer products inventory August 2008 </li></ul><ul><ul><li>803 products on the market </li></ul></ul><ul><ul><li>279% increase since 2006 </li></ul></ul><ul><ul><li>Health & fitness largest category </li></ul></ul>
    10. 10. Nano products – Health & Fitness Category Data courtesy Wilson of Woodrow International Centre for Scholars
    11. 11. Nano-products today <ul><li>Over 235 products now use silver nano-particles for self-cleaning </li></ul><ul><ul><li>Wound dressings </li></ul></ul><ul><ul><li>Cosmetics </li></ul></ul><ul><ul><li>Food storage </li></ul></ul><ul><ul><li>Air purifiers </li></ul></ul><ul><ul><li>Personal care </li></ul></ul>
    12. 12. Nanotechnology – Enabled by ‘seeing’ <ul><li>The invention of the Atomic Force Microscope (AFM) and electron microscope (EM) have enabled us to see into the nano world and begin to manipulate individual atoms. </li></ul>Graphite superlattice 5 nm periodicity C 60 on Si (111)
    13. 13. Nanotechnology in space <ul><li>Future space applications include: </li></ul><ul><ul><li>High strength CNT materials for a space elevator </li></ul></ul><ul><ul><li>(foreseen by Arthur C. Clarke in ‘Fountains of Paradise’ set in Sri Lanka – elevator starts from top of Sigiriya!) </li></ul></ul><ul><ul><ul><li>The only material exhibiting the required strength today </li></ul></ul></ul><ul><ul><li>CFE guns to replace existing “thrusters” </li></ul></ul><ul><ul><ul><li>Lighter and lower energy requirements </li></ul></ul></ul>Courtesy of NASA
    14. 14. Nanocomposites for Photovoltaic Energy Harvesting and Storage Gehan A. J. Amaratunga Electrical Engineering Division, Engineering Dept, University of Cambridge Cambridge UK ePEC Electronics, Power & Energy Conversion
    15. 15. What is the difference between PV energy generation and energy harvesting? <ul><li>PV Energy generation: An alternative to conventional electricity generation technologies for grid connected power </li></ul><ul><li>PV Energy harvesting: capturing light energy in an opportunistic manner from the environment. Generally lower intensity than direct sunlight and aimed at providing an energy source for distributed electronic environments </li></ul>
    16. 16. Solar PV Energy Generation – An ‘expensive’ technology? <ul><li>€ 30 billion solar market by 2010 </li></ul><ul><li>30% global solar market growth since 1996 – 50% since 2003 </li></ul><ul><li>Demand so high, prices have gone up! </li></ul>
    17. 17. Solar PV generation almost entirely Si cell based
    18. 18. Alternative cell technologies which are ‘cheaper’ not required for growth of solar power generation. A new Si industry growing rapidly with massive investment in new capacity
    19. 19. PV Energy harvesting requires alternative and ‘cheap’ cell technologies as they have to be deployed in environments which are unsuitable for Si – e.g flexible substrates such as clothing <ul><li>Powering of autonomous sensing and communication electronics for information gathering </li></ul>
    20. 20. Nanocomposite cells <ul><li>In a nanomposite cell the semiconducting element is scaled to nanometer scale dimensions – e.g a 50nm dia wire – and dispersed in a polymer( flexible) matrix. </li></ul><ul><li>The cell performance is determined by the ‘ensemble’ behaviour of the semiconducting nanowires </li></ul>
    21. 21. Materials when taken down to the < 50nm scale can exhibit physical and chemical properties not seen in bulk phases – e.g. CNT vs graphite <ul><li>Accepting that synthesis can be carried out on a large scale, exploitation of these properties will require: </li></ul><ul><li>Technologies for placement, contacts,integration etc of individual objects with scales < 50nm in at least two dimensions. </li></ul><ul><li>OR </li></ul><ul><li>Dispersion of nanoscale particles in a host matrix, with ‘ensemble’ behaviour of the particles in the matrix enabling enhanced physical/chemical performance. </li></ul><ul><li>The Nanocomposite </li></ul>
    22. 22. MWCNT NEMS Switch: Gate voltage applied to deflect suspended CNT to make contact with source. source drain gate Example of Category 1 Research at Cambridge: S.N. Cha et al, APL 2005
    23. 23. <ul><li>Deterministically and spatially controlled growth of CNTs for ‘ensemble’ field emission. </li></ul>Arrays Electron source Electron source Examples of Category 1/2 Research at Cambridge
    24. 24. Nanocomposite Research – Category 2 <ul><li>Specially suited for energy conversion and storage: </li></ul><ul><li>Polymer – CNT solar cells </li></ul><ul><li>Supercapcitors </li></ul><ul><li>Batteries/fuel cells </li></ul>
    25. 25. Zinc Oxide Nanowires Z.L. Wang, MRS Bulletin 32 (2007) <ul><li>Direct wide bandgap material (3.37 eV) </li></ul><ul><li>Large exciton binding energy (60 meV) </li></ul><ul><li>Transparent and semi-conducting </li></ul><ul><li>Piezoelectric, pyroelectric </li></ul><ul><li>Photoconducting </li></ul><ul><li>Bio-safe and biocompatible </li></ul><ul><li>Many structures…. </li></ul>
    26. 26. Zinc Oxide Nanowire Growth (CVD) ZnO (s) + C (s)  Zn (gas) + CO (gas) Hongjin Fan et al. Nanotechnology 17 (2006) Silicon Sapphire
    27. 27. Zinc Oxide Nanowire Characterization 2.58 Å < 001 > 01-10 0002 CNT@Cambridge Group
    28. 28. Hydrothermal ZnO Nanowire Synthesis Step 1: Spin coat zinc acetate Step 2: NW growth in solution Zinc salt hydrolysis, HMTA 90 º C <ul><li>High density, yield, quality nanowires </li></ul><ul><li>Economic and environmental </li></ul><ul><li>Any type of substrate can be used </li></ul><ul><li>Scalable to large area </li></ul>
    29. 29. ZnO Nanowire Characterization
    30. 30. <ul><li>= 800 – 1080 cm 2 /Vs </li></ul><ul><li>ON/OFF ~ 10 6 </li></ul>
    31. 31. ZnO Nanowire Electrical Properties  = 18 - 44 Ω .cm
    32. 32. SWNT Thin Films with ZnO NWs ZnO Nanowires SWNT TF Parekh, Fanchini, Eda, Chhowalla APL 90 (2007) SWNT Network
    33. 33. ZnO NW - SWNT TF OPVs 100 mW/cm 2 Unalan et al. to be submitted Substrate
    34. 34. Use of nanostructured electrodes to have ‘area’ concentrator cells. For fixed material, target is large h but small d, l Cell 1: interpenetrated junction Cell 2: interpenetrated electrodes
    35. 35. Vertically aligned CNT – a-Si:H cell CNT a-Si:H (n-i) ITO W Fig 2. A schematic diagram showing the periodic CNT arrays offer multiple absorption opportunities in amorphous silicon photovoltaic cell.
    36. 36. a-Si:H on CNT cell Periodic CNT array a-Si: H and ITO coated CNT array
    37. 38. Fabrication sequence for CNT/a-Si:H/ITO cell I Deterministic MWCNT growth II Conformal n+ and i-a-Si:H III – ITO transparent contact IV Completed array (hole collector)
    38. 39. 500 nm MWCNT a-Si:H ITO Capacitance enhancement (i) with CNT (ii) no CNT 40 nm TEM and EDX
    39. 40. Performance of photovoltaic devices with and without CNTs arrays when illuminated with normal incident light. (b) Performance of solar cell with dot pattern CNTs electrode when illuminated with light from different incident angles
    40. 41. Wavelength dependency of I sc enhancement PV-1 PV-2 Filtered PV response PV-1 PV-2 Ⅰ Ⅱ Ⅰ Ⅱ
    41. 42. PV cell on flexible carbon fibre fabric <ul><li>Electrospun carbon fibre </li></ul><ul><li>ZnO nanowires gown directly on fibre </li></ul><ul><li>‘ black dye’ light absorber </li></ul><ul><li>Ionic counter electrode </li></ul>
    42. 43. Flexible carbon fabric <ul><li>SEM image of the carbonized carbon fibre fabric with an average diameter of 1.16 µm. </li></ul>10  m
    43. 44. ZnO grown directly on carbon fibre
    44. 45. PV Cell
    45. 46. A room temperature processed solar cell on flexible substrate A novel ionic liquid was synthesized by grafting polyvinyl alcohol (PVA) with ionic liquid 1-butyl-3-vinylimidazolium bromide (VIC4Br) under the irradiation of a 60Co- γ source.
    46. 47. Ionic liquid based solid dye sensitised PV cell
    47. 48. Reverse process – Light emission from ZnO NW composite <ul><li>Flexible & transparent device </li></ul><ul><li>Cheap and simple to fabricate, at low temperature (max. 150ºC) </li></ul><ul><li>Fully solution processable, no vacuum required. </li></ul>Device Structure 220nm
    48. 49. LED Fabrication – Hydrothermal NW growth Step 1: Hydrothermal Growth of ZnO nanowires on ITO coated glass <ul><li>Simple, low temperature method </li></ul><ul><li>High density, yield, quality nanowires </li></ul><ul><li>Economic and environmental </li></ul><ul><li>Any type of substrate can be used </li></ul><ul><li>Scalable to large area </li></ul><ul><li>Controllable dimensions </li></ul>Greene et al. Nano Lett. 5 (2005) Kim et al. APL 89 (2006) Vayssieres et al. Adv. Mater 15 (2003)
    49. 50. Optical Properties Transmission Spectra Photoluminescense spectra 400 500 600 700 800 900 0 20 40 60 80 100 3,6 3,2 2,8 2,4 2,0 1,6 % Transmission Wavelength  (nm) Transmission spectrum -ZnO wires on ITO+glass
    50. 51. LED Fabrication Step 1: Hydrothermal Growth of ZnO nanowires on ITO coated glass Step 2: Spin coat insulating layer, dry and etch the tips No plasma 1 min 3 min 6min
    51. 52. LED Fabrication Step 1: Hydrothermal Growth of ZnO nanowires on ITO coated glass Step 2: Spin coat insulating layer, dry and etch the tips Step 3: Spin coat organic p-type layer <ul><li>poly(styrenesulfonate) doped poly(3,4-ethylenedioxythiophene) ( PEDOT:PSS) </li></ul><ul><li>Highly p-doped hole injection layer </li></ul><ul><li>Water based solvent </li></ul><ul><li>Highly stable </li></ul>
    52. 53. LED structure Step 1: Hydrothermal Growth of ZnO nanowires on ITO coated glass Step 2: Spin coat insulating layer, dry and etch the tips Step 3: Spin coat organic p-type layer Step 4: Evaporate metal contact
    53. 54. LED diode Characteristic
    54. 55. Light Emission <ul><li>Narrow band emission </li></ul><ul><li>Emission Threshold: ~9V </li></ul>??? A. Nadarajah et al. Nanoletters, December 2007
    55. 56. Origin of ultra-sharp emission peak at 450nm <ul><li>Due to the large barrier, electron and hole accumulation occurs outside the depletion layer </li></ul><ul><li>At this point, recombination probability is high. </li></ul>~450nm Energy levels for materials used Device under forward bias
    56. 57. 450nm <ul><li>ZnO is known to posses defect states, specially so, on solution grown wires </li></ul><ul><li>If one on these defects emits at 450nm, even though intensity may be low, if it is long lived, it can be constructively amplified by ZnO NW cavity. </li></ul>Oriented ZnO NW acting as cavity for light Amplification Experimental length ~220nm
    57. 58. Energy Storage : Two aspect are important – energy density and power density
    58. 59. Capacitive energy storage
    59. 63. Ragone plot and battery discharge curve
    60. 64. Li ion BATTERY TECHNOLOGY TRENDS ENERGY SOURCES New Lithium-based chemistries provide potential for further battery capacity improvement. A major limitation of Li ion batteries remains their loss of capacity with time irrespective of the number of charge-discharge cycles. A capacity loss of 20% per year is common.
    61. 65. A Practical solution would be an integrated device in which it appears as if a Li ion battery is connected in parallel with a supercapacitor + + - -                                                                   
    62. 66. Solid Li ion batteries <ul><li>No liquid electrolyte ( Li salt in an organic solvent) – allows removal of metal casing required to contain liquid. Light weight batteries. </li></ul><ul><li>But solid electrolyte does not take up Li very well – ion conducting polymer composite, higher internal resistance. </li></ul><ul><li>Energy density can be enhanced by increasing Li take up of the anode – currently intercolated carbon. </li></ul>
    63. 67. Solid Supercapacitors <ul><li>Enhanced Electrode areas with solid High relative permittivity dielectric. </li></ul><ul><li>Nanocomposite of electrode and dielectric? </li></ul><ul><li>Pioneering a new nanocomposite system which results in an interpenetrating Li-ion battery and supercapcitor network. </li></ul>
    64. 68. New method for bulk production of nanocarbon materials which can be suitable for energy storage applications Nature, 506 (414), 2001 Nano-onions
    65. 69. Carbon nanohorns : Bulk synthesis by arc in liquid nitrogen. Enhanced take up of metal/catalyst particles. Suitable for both Li-ion anode and Pt catalyst on electrode for fuel cells Nanotech.546(15)2004
    66. 70. Synthesis of Nanohorn-metal composite Carbon 95(42)2004
    68. 72. NP agglomerates are 20-100nm diameter spherical structures with concave and convex curves inside the structure. Distance between the graphene sheets, d=0.376nm compared to ordinary graphite 0.336nm. Chemical and surface energy differences are expected because of the highly curved surface structures, and possible edge formations at the surface ELECTRONICS, POWER AND ENERGY CONVERSION GROUP
    69. 73. Surface Area Measurements of SWNHs Nitrogen adsorption isotherms taken at 77K for as-produced and modified SWNH (oxidized in air at 350 ºC). 1000 ~1500 m 2 /g ELECTRONICS, POWER AND ENERGY CONVERSION GROUP
    70. 74. Controlled MWCNT growth as basis for Supercapacitor electrodes grown single multi-wall carbon nanotube Catalyst shape Number of MWCNT  Process is very simple  High Integration density ; vertical structure  Various applications Structure effect Function part Nano capacitor Nano switch <200nm K B K Teo et al, Nanotechnology 14, 2003
    71. 75. - Metal –Insulator-MWCNT-Metal Capacitor <ul><li>Very simple process </li></ul><ul><li>High effective electrode area due to MWCNT </li></ul>Formation of Catalyst Growth of MWCNT Deposition of Insulator Deposition of Metal electrode
    72. 76. II. Result & Discussion ( 1) MICNM capacitor <ul><li>-diameter  70nm </li></ul><ul><li>height  3.5  m </li></ul>Growth of MWCNT by PECVD Deposition Si 3 N 4 by PECVD -thickness  65nm (wall) 85nm (substrate) Deposition Al by Angular evaporation -thickness  40nm (wall) 80nm (substrate)
    73. 77. - Electrical characteristics measurement Structure I –point MWCNTs 1um 1um Structure II-line MWCNTs 1um Ni catalyst was patterned in a dot shape (<180nm, diameter) with 1  m pitch over a 200um x 200um area. Top electrode : 220um x 320um Ni catalyst was patterned in a line shape with 180nm width, 200um length, and 1  m pitch over a distance of 200  m Top electrode : 220um x 320um
    74. 78. Capacitance Leakage current -The capacitance of the dot pattern and line pattern are about two and six times higher respectively compared to an equivalent MIM structure in same area. -This is mainly due to an increase in the effective electrode area by incorporation of vertical MWCNTs. - One MICNM structure is about 1 fF -The leakage current density is a little bit higher than in the standard MIM structure, however, this is still acceptable for many applications
    75. 79. <ul><li> On & Off state is very clear ; mechanical movement of CNT </li></ul><ul><li>MWCNTs do not return to original position without applied biases </li></ul>- NEM switch with MWCNT 1um V 2nd =0.05V D G S D G S D G S Off On
    76. 82. Joint programme with Nokia to explore flexible energy storage systems
    77. 84. Conclusions <ul><li>Polymer nanocomposites can significantly enhance the performance of organic photovoltaic devices. </li></ul><ul><li>The same concept of distributed and interpenetrating junctions can be extended to electrodes and ion conducting polymers. These would be applicable in Li-ion batteries and supercapacitors. </li></ul><ul><li>New nanomaterial structures which can be synthesised by bulk methods should be explored in nanocomposites for energy storage. </li></ul><ul><li>Engineered structures, such as vertically aligned and optimally placed carbon MWCNTs, could form the back bone for enhanced supercapacitors. </li></ul>
    78. 85. Conclusions <ul><li>Polymer nanocomposites allow the opportunity to use inorganic semiconductors in nanowire form for ubiquitous energy harvesting photovoltaic devices. </li></ul><ul><li>High electronic quality ZnO nanowires grown on SWNTs and carbon fibres are suitable for charge separation with polymer and dye absorbers. </li></ul><ul><li>Oriented nanowires and nanotubes allow an additional degree of freedom for optical design of PV cells. </li></ul><ul><li>Narrow band width light emission observed from oriented ZnO/PDOT:PSS heterojunction diodes </li></ul>
    79. 86. Acknowledgements <ul><li>Cambridge </li></ul><ul><li>Emrah Unalan, Pritesh Hiralal , Hang Zhou, Daniel Kuo, Shavari Dalal, Nalin Rupesinghe, Sai Giridhar, Tim Butler </li></ul><ul><li>Nokia Cambridge Research Centre </li></ul><ul><li>Di Wei, Alan Colli, Markku Rouvala </li></ul><ul><li>Rutgers </li></ul><ul><li>Manish Chhowalla </li></ul><ul><li>Tokyo Institute of Technology </li></ul><ul><li>Kenichi Suzuki, Akihiko Tanioka </li></ul><ul><li>Nagoya Institute of Technology </li></ul><ul><li>Yasuhiko Hayashi </li></ul><ul><li>Financial Support </li></ul><ul><li>Samsung Advanced Institute of Technology; </li></ul><ul><li>Nokia – Cambridge Strategic Research Alliance in Nanotechnology </li></ul>