Medium Scale Carbon Nanotube Thin Film Integrated Circuits on Flexible Plastic Substrates

• US 20110147715A1
• Filed: 06/16/2009
• Published: 06/23/2011
• Est. Priority Date: 06/16/2008
• Status: Active Grant

• Current Assignee: Board of Trustees of The University of Illinois, Purdue Research Foundation (The Trustees of Purdue University (d/b/a Purdue University))
• Original Assignee: Purdue Research Foundation (The Trustees of Purdue University (d/b/a Purdue University))
• Inventors: Pimparkar, Ninad, Alam, Muhammad, Cao, Qing, Rogers, John A.
• Granted Patent: US 8,946,683 B2
• Time in Patent Office: Days
• US Class Current: 257/24
• CPC Class Codes: B82Y 10/00 Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• CPC Class Codes: H10K 10/464 Lateral top-gate IGFETs comprising only a single gate
• CPC Class Codes: H10K 10/466 Lateral bottom-gate IGFETs comprising only a single gate
• CPC Class Codes: H10K 71/135 using ink-jet printing
• CPC Class Codes: H10K 71/20 Changing the shape of the active layer in the devices, e.g. patterning
• CPC Class Codes: H10K 85/221 Carbon nanotubes
• CPC Class Codes: Y10S 977/742 Carbon nanotubes, CNTs
• CPC Class Codes: Y10S 977/938 Field effect transistors, FETS, with nanowire- or nanotube-channel region

Abstract

The present invention provides device components geometries and fabrication strategies for enhancing the electronic performance of electronic devices based on thin films of randomly oriented or partially aligned semiconducting nanotubes. In certain aspects, devices and methods of the present invention incorporate a patterned layer of randomly oriented or partially aligned carbon nanotubes, such as one or more interconnected SWNT networks, providing a semiconductor channel exhibiting improved electronic properties relative to conventional nanotubes-based electronic systems.

Claims

1. An electronic device comprising:

a first electrode;

a second electrode; and

a patterned layer of randomly oriented or partially aligned carbon nanotubes provided in one or more interconnected carbon nanotube networks positioned between and in electrical contact with said first electrode and said second electrode, said patterned layer having a thickness less than or equal to 10 nanometers and having one or more void regions without carbon nanotubes;

wherein said one or more void regions provided between said first and second electrodes reduces by at least 20% the number of purely metallic conductive pathways from said first electrode and second electrode in said one or more interconnected carbon nanotube networks.

2. The electronic device of claim 1 wherein said void regions comprise one or more cavities or channels extending through the entire thickness of said patterned layer.

3. The electronic device of claim 1 wherein said void regions are provided in said patterned layer in a periodic spatial distribution.

4. The electronic device of claim 1 wherein said void regions are provided in said patterned layer in an aperiodic spatial distribution.

5. The electronic device of claim 1 wherein said void regions comprise a pattern etched into said carbon nanotube networks of said patterned layer.

6. The electronic device of claim 1 wherein said void regions are filled with one or more insulating or semiconducting materials capable of disrupting metallic conductive pathways in said one or more interconnected carbon nanotube networks from said first and second electrodes.

7. The electronic device of claim 1 wherein said void regions comprise a plurality of cavities in said patterned layer.

8. The electronic device of claim 7 wherein said cavities in said patterned layer have lateral dimensions selected from the range of 50 nanometers to 1000 microns.

9. The electronic device of claim 7 wherein said cavities in said patterned layer have a lateral cross sectional shape selected from the group consisting of rectangle, square, circle, and oval.

10. The electronic device of claim 7 wherein at least a portion of said cavities in said patterned layer do not extend entirely from said first electrode to said second electrode.

11. The electronic device of claim 7 wherein at least a portion of said cavities in said patterned layer extend entirely from said first electrode to said second electrode, thereby defining a plurality of strips of interconnected carbon nanotube networks in said patterned layer.

12. The electronic device of claim 11 wherein cavities in said patterned layer separate said strips such they do not physically contact each other.

13. The electronic device of claim 11 wherein each of said strips has an average width and extends an average length at least 10 times greater than said average width.

14. The electronic device of claim 11 wherein said cavities in said patterned layer define 2 to 1000 of said strips in said patterned layer.

15. The electronic device of claim 14 wherein at least a portion of said strips extend between first and second electrodes and are provided in a parallel orientation.

16. The electronic device of claim 14 wherein at least a portion of said strips of interconnected carbon nanotube networks extend between first and second electrodes and are provided in a serpentine orientation.

17. The electronic device of claim 14 wherein adjacent strips are separated from each other by one or more of said cavities having lateral dimensions large enough to prevent electron transport directly between adjacent strips.

18. The electronic device of claim 11 wherein adjacent strips are separated from each other by an average distance selected over the range of 50 nanometers to 1000 microns.

19. The electronic device of claim 11 wherein at least a portion of said strips has an aspect ratio selected over the range of 10 to 1000.

20. The electronic device of claim 11 wherein each of said strips has an average width selected over the range of 50 nanometers to 1000 microns and a length selected over the range of 500 nanometers to 10000 microns.

21. The electronic device of claim 11 wherein each of said strips have a lateral cross sectional shape selected from the group consisting of rectangular, circular, oval, and trapezoidal.

22. The electronic device of claim 7 wherein said cavities are provided discontinuously along one or more alignment axes extending from said first to said second electrodes.

23. The electronic device of claim 1 wherein said patterned layer is a monolayer or sub-monolayer film of said carbon nanotubes.

24. The electronic device of claim 1 wherein said carbon nanotubes of said patterned layer have an average length selected over the range of 20 nanometers to 100 microns.

25. The electronic device of claim 1 wherein said carbon nanotubes of said patterned layer have a surface concentration selected over the range of 0.2 carbon nanotubes micron⁻

2 to 100 carbon nanotubes micron<sup>−

2</sup>.

26. The electronic device of claim 1 wherein said carbon nanotubes of said patterned layer comprise single walled carbon nanotubes.

27. The electronic device of claim 1 wherein said carbon nanotubes of said patterned layer comprise a mixture of semiconducting nantoubes and metallic nanotubes, wherein there are at least 1.5 times more semiconducting nanotubes than metallic nanotubes.

28. The electronic device of claim 11 wherein said strips of said patterned layer provide a semiconductor channel between said first and second electrodes, wherein said semiconductor channel has a length selected over the range of 50 nanometers and 1000 microns.

29. The electronic device of claim 1 further comprising a substrate provided to support said first electrode, second electrode and said patterned layer, said substrate selected from the groups consisting of a flexible substrate, a rigid substrate, a semiconductor substrate, polymer substrate, a ceramic substrate and a contoured substrate.

30. The electronic device of claim 1 comprising a transistor, wherein said first electrode is a source electrode, said second electrode is a drain electrode and said patterned layer is a semiconductor channel of said transistor.

47. The electronic device of claim 1 wherein said one or more void regions reduces by at least 40% the number of purely metallic conductive pathways in said one or more interconnected carbon nanotube networks.

48. The electronic device of claim 1 wherein said void regions have a thickness selected over the range of 2 nanometers to 10 nanometers.

49. The electronic device of claim 13 wherein each of said strips extends an average length at least 100 times greater than said average width.

50. The electronic device of claim 13 wherein each of said strips extends an average length at least 1000 times greater than said average width.

51. The electronic device of claim 19 wherein at least a portion of said strips has an aspect ratio selected over the range of 50 to 500.

52. The electronic device of claim 27 wherein there are 1.5 to 4 times more semiconducting nanotubes than metallic nanotubes.

55. The electronic device of claim 20 wherein each of said strips has an average width of 5 microns and a length of 100 microns.

56. The electronic device of claim 1 wherein said interconnected carbon nanotube networks include at least one nantube crossing.

31. A method for making an electronic device comprising the steps of:

providing a first electrode;

providing a second electrode; and

providing a patterned layer of randomly oriented or partially aligned carbon nanotubes provided in one or more interconnected carbon nanotube networks positioned between and in electrical contact with said first electrode and said second electrode, said patterned layer having a thickness less than or equal to 10 nanometers and having one or more void regions in said patterned layer without carbon nanotubes;

wherein said one or more void regions provided between said first and second electrodes reduces by at least 20% the number of purely metallic conductive pathways from said first and second electrodes in said one or more interconnected carbon nanotube networks.

32. The method of claim 31 wherein said void regions comprise a plurality of cavities in said patterned layer that extend entirely from said first electrode to said second electrode, thereby defining a plurality of strips of interconnected carbon nanotube networks in said patterned layer.

33. The method of claim 32 wherein cavities in said patterned layer separate said strips such they do not physically contact each other.

34. The method of claim 32 wherein each of said strips has an average width and extends an average length at least 10 times greater than said average width.

35. The method of claim 31 wherein said step of providing a patterned layer of randomly oriented or partially aligned carbon nanotubes provided in one or more interconnected carbon nanotube networks positioned between and in electrical contact with said first electrode and said second electrode comprises the steps of:

providing a precursor layer of said randomly oriented or partially aligned carbon nanotubes in electrical contact with said first and second electrodes;

patterning said precursor layer so as to generate said patterned layer.

36. The method of claim 35 wherein said step of providing said precursor layer in electrical contact with said first and second electrodes is selected from the group consisting of:

growing said carbon nanotubes on a device substrate, thereby generating said precursor layer;

dispersing said carbon nanotubes in a solvent, thereby generating a carbon nanotube solution comprising a suspension of said carbon nanotubes, and depositing said carbon nanotube solution on to a device substrate, thereby generating said precursor layer; and

contact printing said carbon nanotubes on to a device substrate, thereby generating said precursor layer.

37. The method of claim 35 wherein said step of patterning said precursor layer is carried out using one or more photolithography techniques.

38. The method of claim 35 wherein said step of patterning said precursor layer comprises the steps:

providing a layer of resist on said precursor layer;

patterning said resist layer by selectively removing regions of said resist layer, thereby generating exposed regions of said precursor layer; and

removing carbon nanotubes from said exposed regions of said precursor layer, thereby generating said patterned layer comprising said one or more strips extending between said first and second electrodes.

39. The method claim 38 wherein said step of patterning said resist layer is carried out via photolithography, soft lithography, phase shift lithography, electron beam writing lithography or deep ultraviolet lithography.

40. The method claim 38 wherein said step of removing carbon nanotubes from said exposed regions of said precursor layer comprises etching said exposed regions of said precursor layer.

41. The method of claim 31 wherein said step of providing a patterned layer of randomly oriented or partially aligned carbon nanotubes in electrical contact with said first electrode and said second electrode comprises ink jet printing said carbon nanotubes, thermal transfer printing said carbon nanotubes, contact printing said carbon nanotubes, dry transfer printing or screen printing said carbon nanotubes.

42. An transistor comprising:

a source electrode;

a drain electrode;

a gate electrode;

a patterned layer of randomly oriented or partially aligned carbon nanotubes provided in one or more interconnected carbon nanotube networks positioned between and in electrical contact with said source electrode and said drain electrode, said patterned layer having a thickness less than or equal to 10 nanometers and having one or more void regions in said patterned layer without carbon nanotubes;

wherein said one or more void regions provided between said first and second electrodes reduces by at least 20% the number of purely metallic conductive pathways between said source electrode and said drain electrode in said one or more interconnected carbon nanotube networks; and

a dielectric layer positioned between said patterned layer and said gate electrode.

43. The electronic device of claim 42 comprising a thin film transistor.

44. The transistor of claim 42 wherein said transistor has an on/off ratio greater than or equal to 100.

45. The transistor of claim 42 wherein said transistor has a field effect mobility greater than or equal to 0.1 cm² V⁻

1 s<sup>−

1</sup>.

53. The thin film transistor of claim 44 wherein said transistor has an on/off ratio greater than or equal to 1000.

54. The thin film transistor of claim 45 wherein said transistor has a filed effect mobility equal to or greater than 10 cm² V⁻

1 s<sup>−

1</sup>.

46. A method for reducing the number of purely metallic conductive pathways in one or more interconnected carbon nanotube networks provided between a first electrode and second electrode, said method comprising the steps of:

providing a patterned layer of randomly oriented or partially aligned carbon nanotubes provided in one or more interconnected carbon nanotube networks positioned between and in electrical contact with said first electrode and said second electrode, said patterned layer having a thickness less than or equal to 10 nanometers and having one or more void regions in said patterned layer without carbon nanotubes;

wherein said one or more void regions provided between said first and second electrodes reduces by at least 20% the number of purely metallic conductive pathways between said first electrode and said second electrode in said one or more interconnected carbon nanotube networks.