Two-dimensional carbon nanotube liquid crystal films for wafer-scale electronics
Methods of forming films of aligned carbon nanotubes on a substrate surface are provided. The films are deposited from carbon nanotubes that have been concentrated and confined at a two-dimensional liquid/liquid interface. The liquid/liquid interface is formed by a dispersion of organic material-coated carbon nanotubes that flows over the surface of an immiscible liquid within a flow channel. Within the interface, the carbon nanotubes self-organize via liquid crystal phenomena and globally align along the liquid flow direction. By translating the interface across the substrate, large-area, wafer-scale films of aligned carbon nanotubes can be deposited on the surface of the substrate in a continuous and scalable process.
1. A method of forming a film of aligned carbon nanotubes, the method comprising:
forming a liquid dispersion comprising organic material-coated carbon nanotubes dispersed in a first liquid;
forming a channel that is defined by:
a deposition wall;
a confining wall that is separated from the deposition substrate by a gap; and
a second liquid that is immiscible with the liquid dispersion spanning the gap between the deposition wall and the confining wall and providing a channel floor,
cooling the second liquid to a temperature of 15° C. or lower;
flowing the liquid dispersion of organic material-coated carbon nanotubes through the channel, over the cooled second liquid, to form an interface between the liquid dispersion of organic material-coated carbon nanotubes and the cooled second liquid, wherein the organic material-coated carbon nanotubes become concentrated at the interface and aligned within the interface along the flow direction; and
translating the deposition wall across the interface as the liquid dispersion of organic material-coated carbon nanotubes flows through the channel, whereby organic material-coated carbon nanotubes are deposited from the interface onto a surface of the deposition wall.
2. The method of claim 1 , wherein the temperature below ambient temperature is in the range from 15° C. to 1° C.
3. The method of claim 1 , wherein the temperature below ambient temperature is in the range from 12° C. to 5° C.
4. The method of claim 1 , wherein the concentration of carbon nanotubes in the liquid dispersion is in the range from 5 μg/mL to 200 μg/mL.
5. The method of claim 1 , wherein the concentration of carbon nanotubes in the liquid dispersion is in the range from 50 μg/mL to 150 μg/mL.
6. The method of claim 1 , wherein the liquid dispersion of organic material-coated carbon nanotubes has a flow rate in the range from 2 mL/min to 12 mL/min.
7. The method of claim 1 , wherein the surface of the deposition wall and the floor of the channel define a tilt angle in the range from 5° to 85°.
8. The method of claim 7 , wherein the surface of the deposition wall comprises silicon oxide.
9. The method of claim 8 , wherein the organic material is a poly(9,9-dialkyl-fluorene) derivative or a poly(phenyl vinylene) derivative.
10. The method of claim 1 , wherein the liquid dispersion is a non-aqueous liquid dispersion and the second liquid is an aqueous liquid.
11. A method of forming a film of aligned carbon nanotubes, the method comprising:
forming a liquid dispersion comprising organic material-coated carbon nanotubes dispersed in a first liquid;
forming a channel that is defined by:
a deposition wall;
a confining wall that is separated from the deposition substrate by a gap; and
a second liquid that is immiscible with the liquid dispersion spanning the gap between the deposition wall and the confining wall and providing a channel floor, wherein the deposition wall and the floor of the channel define a tilt angle in the range from 5° to 85°,
flowing the liquid dispersion of organic material-coated carbon nanotubes through the channel, over the second liquid, to form an interface between the liquid dispersion of organic material-coated carbon nanotubes and the second liquid, wherein the organic material-coated carbon nanotubes become concentrated at the interface and aligned within the interface along the flow direction; and
translating the deposition wall across the interface as the liquid dispersion of organic-material coated carbon nanotubes flows through the channel, whereby organic material-coated carbon nanotubes are deposited from the interface onto the deposition wall.
12. The method of claim 11 , wherein the deposition wall and the floor of the channel define a tilt angle in the range from 15° to 60°.
13. The method of claim 11 , wherein the concentration of carbon nanotubes in the liquid dispersion is in the range from 5 μg/mL to 200 μg/mL.
14. The method of claim 11 , wherein the concentration of carbon nanotubes in the liquid dispersion is in the range from 50 μg/mL to 150 μg/mL.
15. The method of claim 11 , wherein the liquid dispersion of organic material-coated carbon nanotubes has a flow rate in the range from 2 mL/min to 12 mL/min.
16. The method of claim 11 , wherein the surface of the deposition wall comprises silicon oxide.
17. The method of claim 11 , wherein the organic material is a poly(9,9-dialkyl-fluorene) derivative or a poly(phenyl vinylene) derivative.
18. The method of claim 11 , wherein the liquid dispersion is a non-aqueous liquid dispersion and the second liquid is an aqueous liquid.