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- Dittmer, Staffan, 1970
(författare)
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Development of a method for highly localized growth of carbon nanotubes
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A method for growing carbon nanotubes on chip using highly localizedresistive heating is developed. By deliberately designing molybdenumelectrodes to be highly resistive in a very small region we create amicrometer sized hot-zone where carbon nanotubes can be grown. Due to the limited size of the hot-zone we are able to control thegrowth time very accurately since cooling below growth temperatureis almost instant. The small size of the chamber further helps inefficiently stopping growth by evacuation.Effects of using different catalysts -- Fe and Ni, supported onAl2O3 of different thicknesses or directly in contact with theelectrode and carbon feedstocks are studied using in situRaman spectroscopy and SEM. We find that the choice of catalyst iscrucial in this process - even more so than in similar CVD methods.Using acetylene, C2H2, as carbon feedstock, with 1 nm iron,Fe, supported on 5 nm aluminium oxide, Al2O3, as catalyst, weare able to grow multi-wall nanotubes with diameters of 5-10 nmdirectly on molybdenum electrodes.With ethylene, C2H4, using the same catalyst, we growsingle-wall nanotubes with diameters in the range of 0.7-1.8 nm.Thin multi-wall tubes are also grown using ethylene.Using the resistive growth method we perform sequential growth ofcrossed nanotubes using electric field alignment. We also develop aprocess for making a RF resonator based on low temperature grownarrays of aligned nanotubes.Being able to keep the sample temperature down during growthbenefits the integration of carbon nanotubes with CMOS-technology aswell as bioelectronics, and also permits using low temperaturematerials as building blocks for nanoelectromechanicalstructures on chip. The mean temperature of our samples is 60C during growth.
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| 2. |
- Dittmer, Staffan, 1970, et al.
(författare)
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Electric field aligned growth of single-walled nanotubes
- 2004
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Ingår i: Current Applied Physics. - : Elsevier BV. - 1567-1739. ; 4, s. 595-598
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Tidskriftsartikel (refereegranskat)abstract
- Electric field aligned, single-walled carbon nanotubes are grown between electrodes using thermal chemical vapour deposition (CVD) of methane. The growth occurs on a thin film layered catalyst of aluminium, iron and molybdenum patterned on top of electrodes. The nanotubes bridge 10 μm sized electrode gaps and have a typical diameter of less than 2 nm as measured by Raman spectroscopy and atomic force microscopy. We present electrical transport measurements on a directly grown nanotube which shows p-type semiconducting behaviour.
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| 3. |
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| 4. |
- Dittmer, Staffan, 1970, et al.
(författare)
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In situ Raman studies of single-walled carbon nanotubes grown by local
- 2008
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Ingår i: Chemical Physics Letters. - : Elsevier BV. - 0009-2614 .- 1873-4448. ; 457
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Tidskriftsartikel (refereegranskat)abstract
- Using in situ Raman spectroscopy we investigate single wall carbon nanotube growth on Mo electrodes, using a highly localized resistive heating technique. Small diameter semiconducting single wall nanotubes grow very rapidly when the catalyst support is heated to a temperature of 800 C. The G/D ratio shows an interesting time-dependent behaviour. It first decreases, indicating the presence of amorphous carbon and then significantly increases again after ca. 5 min growth while retaining the position and shape expected for predominantly semiconducting carbon nanotubes.
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| 5. |
- Dittmer, Staffan, 1970, et al.
(författare)
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Local heating method for growth of aligned carbon nanotubes at low ambient temperature
- 2008
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Ingår i: Low Temperature Physics. - : AIP Publishing. - 1063-777X .- 1090-6517. ; 34:10, s. 834-838
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Tidskriftsartikel (refereegranskat)abstract
- We use a highly localised resistive heating technique to grow vertically aligned multiwalled nanotube films and aligned single-walled nanotubes on substrates with an average temperature of less than 100oC. The temperature at the catalyst can easily be as high as 1000 oC but an extremely high temperature gradient ensures that the surrounding chip is held at much lower temperatures, even as close as 1μm away from the local heater. We demonstrate the influence of temperature on the height of multi-walled nanotube films, illustrate the feasibility of sequential growth of single-walled nanotubes by switching between local heaters and also show that nanotubes can be grown over temperature sensitive materials such as resist polymer.
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| 6. |
- Dittmer, Staffan, 1970, et al.
(författare)
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Low ambient temperature CVD growth of carbon nanotubes
- 2006
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Ingår i: Applied Physics A. - : Springer Science and Business Media LLC. - 0947-8396 .- 1432-0630. ; 84, s. 243-246
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Tidskriftsartikel (refereegranskat)abstract
- We show that good quality single-walled and multi-walled carbon nanotubes can be grown on CMOS-compatible metal electrodes at ambient room temperature using highly localised catalyst heating at nanostructured electrodes. The method is relatively straightforward and allows considerable flexibility in the kinds of devices that can be fabricated as well as allowing CVD nanotube growth to take place in the close vicinity of temperature-sensitive materials and devices.
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| 7. |
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| 8. |
- Gromov, Andrei, 1959, et al.
(författare)
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Covalent Amino functionalisation of single walled carbon nanotubes
- 2005
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Ingår i: J. Materials Chem. - : Royal Society of Chemistry (RSC). - 0959-9428 .- 1364-5501. ; 15, s. 3334-3339
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Tidskriftsartikel (refereegranskat)abstract
- Chemical transformation of single-wall carbon nanotubes (SWNT), edge-terminated with carboxylic groups, to SWNT species with amino groups directly attached to the tube open ends has been performed. Different synthetic approaches have been investigated. The reaction products were characterised by FTIR, Raman spectroscopy, XPS and SEM.
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| 9. |
- Mattsson, M, et al.
(författare)
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Dielectrophoresis-induced separation of metallic and semiconducting SWNT in a continuous flow microfluidic system
- 2007
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Ingår i: Journal of Nanotechnology and Nanoscience. - : American Scientific Publishers. - 1533-4880. ; 7, s. 3431-3435
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Tidskriftsartikel (refereegranskat)abstract
- The AC dielectrophoresis-induced separation of metallic and semiconducting single-wall carbon nanotubes has been carried out in a continuous flow microfluidic system with isolated electrodes. The separation has been studied for single-wall carbon nanotube aqueous suspensions with ionic (sodium dodecylsulphate) and non-ionic (TritonX-100) surfactants. The efficiency of separation has been determined with the help of resonant Raman spectroscopy using various excitation energies. The prototype microfluidic cell presently shows somewhat inferior separation efficiency with respect to static dielectrophoretic filtering on arrays of microelectrodes but has potential for improvements. Factors influencing the separation efficiency and scaling up of the process are discussed.
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