7. Carbon Nanotubes. 1. Overview: Global status market price 2. Types. 3. Properties. 4. Synthesis. MWNT / SWNT zig-zag / armchair / chiral

Transcription

1 7. Carbon Nanotubes 1. Overview: Global status market price 2. Types MWNT / SWNT zig-zag / armchair / chiral 3. Properties electrical others 4. Synthesis arc discharge / laser ablation / CVD 5. Applications active: diode / FET passive: (transparent) conductor, filament 1

2 ITRS2009 2

3 3

4 NASA's Morphing Glider will have flexible CNT wings that move like a hawk's. The wings will curl, twist, extend and twitch.(courtesy of NASA) Scanning Electron-Microscopy (SEM) image of a CNT attached to a cantilever tip. Seldon Labs' nanotubefilter provides reliably clean water, nearly free of bacteria and viruses (Courtesy of Seldon Labs). Nissan's X-Trailsport-utility vehicle has CNT-reinforced bumpers (Courtesy of Nissan). 4

5 Overview: CNT Global status 5

6 Overview: CNT Prices PRODUCT DESCRIPTION CARBONACEOUS PURITY* PRICE** MINIMUM ORDER AP-SWNT As prepared 40-60% $50/g 2 grams P2-SWNT Purified, low functionality 70-90% $400/g 0.5 grams P3-SWNT Purified, high functionality 80-90% $400/g 0.5 grams P5-SWNT P7-SWNT P8-SWNT Organic soluble (functionalized with ODA) Water soluble (functionalized with PEG) Water soluble (functionalized with PABS) 80-90%(50% SWNT loading) $150/100mg 0.1 grams 80-90% (70% SWNT loading) $150/100mg 0.1 grams 80-90%(30% SWNT loading) $150/100mg 0.1 grams The current price schedule for our AP-Grade, single-walled carbon nanotube (SWNT) material is: Quantity Price More than 100 grams $60/g grams $80/g Less than 50 grams $100/g 18 July 07 6

7 1. Overview 2. Types 7. Carbon Nanotubes Allotropes of Carbon MWNT / SWNT zig-zag / armchair / chiral 3. Properties 4. Synthesis 5. Applications 7

8 Allotropes of Carbon Some allotropes of carbon: a) diamond; b) graphite; c) lonsdaleite; d f) fullerenes (C 60, C 540, C 70 ); g) amorphous carbon; h) carbon nanotube. 8

9 MWNTs Discovery still in dispute (see article below). But usually (mis-)credit Iijima who published TEM image of MWNT in M. Monthioux, "Who should be given the credit for the discovery of carbon nanotubes?, CARBON 44: 1621 (2006). 9

10 SWNTs Single-wall nanotubes 10

11 11

12 7. Carbon Nanotubes 1. Global status and market 2. Types 3. Properties electrical others 4. Synthesis 5. Applications 12

13 13

14 Armchair Zig-zag Because of the symmetry and unique electronic structure of graphene, the structure of a nanotube strongly affects its electrical properties. For a given (n,m) nanotube, if n - m is a multiple of 3, then the nanotube is metallic, otherwise the nanotube is a semiconductor. 14

15 significantly reduce electromigration 15

16 ~$ /g in 2005 as-produced arc discharge SWNTs for ~$50-100/g in

17 7. Carbon Nanotubes 1. Global status and market 2. Types 3. Properties 4. Synthesis arc discharge / laser ablation / CVD 5. Applications 17

18 Arc Discharge In 1992 Thomas Ebbesen and Pulickel M. Ajayan of the NEC Fundamental Research Laboratory in Tsukuba, Japan, published the first method for making macroscopic quantities of nanotubes. It is almost Frankensteinian in its design: wire two graphite rods to a power supply, place them millimeters apart and throw the switch. As 100 amps of juice spark between the rods, carbon vaporizes into a hot plasma (right).some of it recondenses in the form of nanotubes. Typical yield: Up to 30 percent by weight Advantages: High temperatures and metal catalysts added to the rods can produce both single-walled and multiwalled nanotubes with few or no structural defects. Limitations: Tubes tend to be short (50 microns or less) and deposited in random sizes and directions. 18

19 CVD Morinubo Endo of Shinshu University in Nagano, Japan, was the first to make nanotubes with this method, which is called chemical vapor deposition (CVD). This recipe is also fairly simple. Place a substrate in an oven,heat to 600 degrees Celsius and slowly add a carbon-bearing gas such as methane. As the gas decomposes, it frees up carbon atoms, which can recombine in the form of nanotubes. Jie Liu and his colleagues at Duke University recently invented a porous catalyst that they claim can convert almost all the carbon in a feed gas to nanotubes. By printing patterns of catalyst particles on the substrate, Hongjie Dai and his colleagues at Stanford University have been able to control where the tubes form (left) and have been working to combine this controlled growth with standard silicon technology. Typical yield: 20 to nearly 100 percent Advantages: CVD is the easiest of the three methods to scale up to industrial production. It may be able to make nanotubes of great length, which is necessary for fibers to be used in composites. Limitations: Nanotubes made this way are usually multiwalled and are often riddled with defects. As a result, the tubes have only one tenth the tensile strength of those made by arc discharge. 19

20 Laser Ablation Richard Smalley and his co-workers at Rice University were blasting metal with intense laser pulses to produce fancier metal molecules when the news broke about the discovery of nanotubes. They swapped the metal in their setup for graphite rods and soon produced carbon nanotubes by using laser pulses instead of electricity to generate the hot carbon gas from which nanotubes form (left). Trying various catalysts, the group hit on conditions that produce prodigious amounts of single-walled nanotubes. Typical yield: Up to 70 percent Advantages: Produces primarily singlewalled nanotubes, with a diameter range that can be controlled by varying the reaction temperature. Limitations: This method is by far the most costly, because it requires very expensive lasers. 20

21 Metal catalysts as nucleation centres 21

22 1. Overview 2. Types 3. Properties 7. Carbon Nanotubes 4. Synthesis 5. Applications active: FET / SET / LED passive: (transparent) conductor, filament 22

23 as-grown CNTs p-type V sd = 5 mv 23

24 Intramolecular logic gates Potassium evaporation through window opened by EBL. 24

25 Electronic devices based on purified carbon nanotubes grown by high-pressure decomposition of carbon monoxide, Nature Materials 4, 1-4 (01 Aug 2005) 25

26 200 nm 20 nm AFM tip in tapping mode. Metallic NT used. 26

27 electron injection hole injection 27

28 CNT field emission lamps arrayed in a 5-by-7 matrix. (Courtesy of Noritake Co. Ltd.) 28

29 29 NB: for metals n ~ 1 o T T o n

30 Schematic illustration of a CNT-based field emission display 25 CNT TV from Applied Nanotech, a subsidiary of Nano- Proprietary, Inc. 30

31 Vertical nanotube clusters A cold-cathode lightingtube element with a carbon nanotube emitter (Ahwahnee Technology). 31

32 CNTs Attractive Alternative for Interconnects Semiconductor International, 5/1/2007 densification for interconnects Side view of a CNT bundle end before (left) and after (right) densification process. Recipe 2 CNT bundles before (left) and after (right) densification A/cm 2

33 Conclusions CNTs are a new class of materials with unique electrical, mechanical, thermal properties Applications in electronics include FETs, logic gates, LEDs, flat-panel displays, light bulbs Graphene nanoribbons (GNRs)! 33