PURIFICATION OF CARBON NANOTUBES VIA SELECTIVE HEATING

• US 20160133843A1
• Filed: 04/03/2014
• Published: 05/12/2016
• Est. Priority Date: 04/04/2013
• Status: Active Grant

• Current Assignee: Board of Trustees of The University of Illinois, Northwestern University, University of Miami
• Original Assignee: Board of Trustees of The University of Illinois, Northwestern University, University of Miami
• Inventors: WILSON, William L., JIN, Sung Hun, DUNHAM, Simon N., XIE, Xu, ISLAM, Ahmed, DU, Frank, SONG, Jizhou, ROGERS, John A., HUANG, Yonggang
• Granted Patent: US 9,825,229 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: C01B 2202/22 Electronic properties
• CPC Class Codes: C01B 2202/34 Length
• CPC Class Codes: C01B 32/17 Purification
• CPC Class Codes: G01N 21/62 Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
• CPC Class Codes: H01L 21/02606 Nanotubes carbon nanotubes H10K85/211
• CPC Class Codes: H01M 4/1393 of electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
• CPC Class Codes: H10K 71/13 using printing techniques, e.g. ink-jet printing or screen printing
• CPC Class Codes: H10K 71/311 Purifying organic semiconductor materials
• CPC Class Codes: H10K 85/221 Carbon nanotubes
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

The present invention provides methods for purifying a layer of carbon nanotubes comprising providing a precursor layer of substantially aligned carbon nanotubes supported by a substrate, wherein the precursor layer comprises a mixture of first carbon nanotubes and second carbon nanotubes; selectively heating the first carbon nanotubes; and separating the first carbon nanotubes from the second carbon nanotubes, thereby generating a purified layer of carbon nanotubes. Devices benefiting from enhanced electrical properties enabled by the purified layer of carbon nanotubes are also described.

Claims

1. A method for purifying a layer of carbon nanotubes comprising:

providing a precursor layer of substantially aligned carbon nanotubes supported by a substrate, wherein said precursor layer comprises a mixture of first carbon nanotubes and second carbon nanotubes;

covering said precursor layer of carbon nanotubes with a thermocapillary resist, wherein said thermocapillary resist is in thermal contact with at least a portion of said carbon nanotubes;

selectively heating said first carbon nanotubes, thereby causing thermocapillary flow of said thermocapillary resist away from said first carbon nanotubes to expose said first carbon nanotubes; and

separating said first carbon nanotubes from said second carbon nanotubes, thereby generating a purified layer of carbon nanotubes.

3. The method of claim 1, wherein said purified layer of carbon nanotubes forms a semiconductor channel between first and second electrodes.

4. The method of claim 1, wherein said selective heating results from absorption of electromagnetic radiation, electronic resistance, mobility, direct thermal contact or electromagnetic induction.

5. The method of claim 1, wherein said carbon nanotubes are single-walled carbon nanotubes (SWNTs).

6. The method of claim 1, wherein said carbon nanotubes are multi-walled carbon nanotubes (MWNTs).

7. The method of claim 1, wherein said first carbon nanotubes are metallic carbon nanotubes and said second carbon nanotubes are semiconducting carbon nanotubes.

8. The method of claim 1, wherein said step of providing said precursor layer is selected from the group consisting of:

growing said substantially aligned carbon nanotubes on said substrate comprising a guided growth substrate, thereby generating said precursor layer; and

printing said substantially aligned carbon nanotubes onto said substrate, thereby generating said precursor layer.

9. The method of claim 8, wherein said step of providing said precursor layer of substantially aligned carbon nanotubes comprises ink jet printing, thermal transfer printing, contact printing, dry transfer printing or screen printing said carbon nanotubes.

10. The method of claim 1, wherein said carbon nanotubes have an average length selected from a range of 20 nanometers to 100 microns.

11. The method of claim 1, wherein an average spacing between adjacent carbon nanotubes of said precursor layer is selected from a range of 2 nm to 100 μ

m.

13. The method of claim 1, wherein a surface concentration of carbon nanotubes of said precursor layer is selected from a range of 0.2 carbon nanotubes micron⁻

2 to 100 carbon nanotubes micron<sup>−

2</sup>.

14. The method of claim 1, wherein said precursor layer of substantially aligned carbon nanotubes includes less than 100 carbon nanotube crossings per square micron.

15. The method of claim 1, wherein said layer of substantially aligned carbon nanotubes has a thickness less than or equal to 10 nanometers.

16. The method of claim 1, wherein said layer of substantially aligned carbon nanotubes is a monolayer film or a substantially monolayer film.

17. The method claim 1, wherein said step of separating comprises etching said first carbon nanotubes.

18. The method of claim 1, wherein said step of separating comprises removing said first carbon nanotubes from said precursor layer.

19. The method of claim 1, wherein said step of separating comprises removing said second carbon nanotubes from said precursor layer.

20. The method of claim 1 further comprising removing said thermocapillary resist after said step of separating.

21. The method claim 1, wherein said selective heating is provided by application of electromagnetic energy, current, an electric field, a magnetic field, microwave energy or laser radiation.

22. The method of claim 7, wherein said selective heating comprises absorption of energy by said metallic carbon nanotubes, wherein said energy is insufficient to overcome the Schottky barrier of said semiconducting carbon nanotubes.

23. The method of claim 1, wherein a ratio of a temperature increase of said first carbon nanotubes to a temperature increase of said second carbon nanotubes during said step of selective heating is 1.25 or greater.

24. The method of claim 1, wherein an average temperature gradient within said thermocapillary resist proximate to said first carbon nanotubes is at least 1 K/μ

m.

25. The method of claim 1, wherein said selective heating is provided by one or more of an optical source, a microwave source, a laser source, a DC source, an AC source, or an acoustic source.

27. The method of claim 1, wherein said carbon nanotubes of said precursor layer are in electrical contact with a source electrode, a drain electrode and a gate electrode.

28. The method of claim 27, wherein said selective heating is provided by one or more of a DC source and an AC source delivering a power per carbon nanotube selected from a range of 5 μ

W/μ

m/tube to 50 μ

W/μ

m/tube to said source electrode.

29. The method of claim 28, wherein said source is pulsed at a frequency selected from a range of 1 Hz to 100 MHz.

30. The method of claim 28, wherein said source is activated for a duration selected from a range of 0.1 μ

s to 300 minutes.

31. The method of claim 25, wherein said laser source produces radiation having an energy selected from a range of 100 nJ to 100 mJ.

32. The method of claim 25, wherein said laser source produces radiation having a power less than 1000 J/m².

33. The method of claim 25, wherein said laser source produces radiation having a wavelength selected from a range of 0.1 μ

m to 20 μ

m.

34. The method of claim 25, wherein said laser source is pulsed at a frequency selected from a range of 0 Hz (CW) to 100 MHz.

35. The method of claim 25, wherein said laser source is activated for a duration selected from a range of 1 ns to 300 minutes.

36. The method of claim 1, wherein said carbon nanotubes of said precursor layer are in electromagnetic communication with at least one microwave antennae.

37. The method of claim 36, wherein said electromagnetic communication comprises physical contact, electrical contact or both physical and electrical contact.

38. The method of claim 36, wherein said electromagnetic communication does not comprise physical contact.

39. The method of claim 25, wherein said microwave source produces radiation having an energy selected from a range of 50 J/sec to 10 kJ/sec.

40. The method of claim 25, wherein said microwave source is pulsed at a frequency selected from a range of 0 Hz (CW) to 100 MHz.

41. The method of claim 25, wherein said microwave source is activated for a duration selected from a range of 1 μ

s to 300 minutes.

42. The method of claim 36, wherein said selective heating comprises differential absorption of a preselected wavelength of radiation between said first carbon nanotubes and said second carbon nanotubes, wherein said first carbon nanotubes absorb more than 1.25 times as much energy as said second carbon nanotubes.

43. The method of claim 42, wherein said preselected wavelength is selected from a range of 300 nm to 20 μ

m.

44. The method of claim 1, wherein said first and second carbon nanotubes of said precursor layer are in electrical contact with a first electrode and a second electrode.

45. The method of claim 44, wherein an electrode bias voltage between said first electrode and said second electrode is selected from a range of 0.01 V to 100 V.

46. The method of claim 44, wherein said first and second electrodes are interdigitated.

47. The method of claim 44, wherein said selective heating is provided by one or more of a DC source and an AC source delivering a current selected from a range of 0.01 mA to 100 A.

48. The method of claim 47, wherein said source is pulsed at a frequency selected from a range of 1 Hz to 100 MHz.

49. The method of claim 47, wherein said source is activated for a duration selected from a range of 0.1 μ

s to 100 minutes.

50. The method of claim 1, wherein said thermocapillary resist has a room temperature viscosity selected from a range of 0.5 Pa·

s to 100 Pa·

s.

51. The method of claim 1, wherein said thermocapillary resist comprises a conformal layer on and between said carbon nanotubes.

52. The method of claim 51, wherein said thermocapillary resist is in physical contact with said carbon nanotubes.

53. The method of claim 1, wherein said thermocapillary resist comprises a substantially uniform layer.

54. The method of claim 53, wherein said substantially uniform layer has a thickness selected from a range of 1 nm to 10 μ

m.

55. The method of claim 53, wherein said substantially uniform layer has a thickness less than or equal to 500 nm.

56. The method of claim 53, wherein said substantially uniform layer is a continuous layer.

57. The method of claim 1, wherein at least 1% of a lateral cross section of each of said first carbon nanotubes is exposed by said step of selectively heating said first carbon nanotubes.

58. The method of claim 1, wherein said thermocapillary resist comprises a molecular organic species.

59. The method of claim 58, wherein said thermocapillary resist is selected from the group consisting of α

,α

,α

′

-Tris(4-hydroxyphenyl)-1-ethyl-4-isopropylbenzene, polymethylmethacrylate (PMMA), polystyrene (PS), poly(styrene-dimenthylsiloxane) (PS-PDMS);

oligosaccharide-trimethylsilylstyrene, and polyhedral oligomeric silsesquioxane (POSS).

60. The method of claim 1, wherein said thermocapillary resist comprises a molecular weight selected from a range of 50 g/mol to 1000 kg/mol.

61. The method of claim 1, wherein said substrate is selected from the group consisting of a flexible substrate, a rigid substrate, a semiconductor substrate, polymer substrate, a ceramic substrate and a contoured substrate.

2. A method for making an electronic device comprising:

providing a precursor layer of substantially aligned carbon nanotubes supported by a substrate, wherein said precursor layer comprises a mixture of first carbon nanotubes and second carbon nanotubes;

covering said precursor layer of carbon nanotubes with a thermocapillary resist, wherein said thermocapillary resist is in thermal contact with at least a portion of said carbon nanotubes;

selectively heating said first carbon nanotubes, thereby causing thermocapillary flow of said thermocapillary resist away from said first carbon nanotubes to expose said first carbon nanotubes;

separating said first carbon nanotubes from said second carbon nanotubes, thereby generating a purified layer of carbon nanotubes; and

providing one or more device component structures in electrical or physical contact with said purified layer of carbon nanotubes, thereby making said electronic device.

12. (canceled)

26. (canceled)

62. A method for purifying a layer of carbon nanotubes comprising:

providing a precursor layer of substantially aligned carbon nanotubes supported by a substrate, wherein said precursor layer comprises a mixture of first carbon nanotubes and second carbon nanotubes; and

selectively heating said first carbon nanotubes to separate said first carbon nanotubes from said second carbon nanotubes, thereby providing a purified layer of carbon nanotubes comprising at least 50% of said first or said second carbon nanotubes.

63-69. -69. (canceled)

70. An electronic device comprising:

a first electrode;

a second electrode; and

a layer of substantially aligned carbon nanotubes positioned between and in electrical contact with said first electrode and said second electrode, wherein said layer of substantially aligned carbon nanotubes comprises at least 90% semiconducting carbon nanotubes.