Substrate patterning by electron emission-induced displacement
Disclosed are methods and devices for patterning micro- and/or nano-sized pattern elements on a substrate using field emitted electrons from an element. Disclosed methods and devices can also be utilized to form nano- and micron-sized depressions in a substrate according to a more economical process than as has been utilized in the past. Methods include single-step methods by which structures can be simultaneously created and located at desired locations on a substrate. Methods include the application of a bias voltage between a probe tip and a substrate held at a relatively close gap distance. The applied voltage can promote current flow between the probe and the substrate via field emissions. During a voltage pulse, and within predetermined energy levels and tip-to-surface gap distances, three dimensional formations can be developed on the substrate surface.
1. A method for forming an element on a substrate comprising:
locating a probe tip at a distance of less than about 5 μm from a surface of a substrate such that there is a gap between the probe tip and the substrate surface, the substrate comprising a semiconducting material;
establishing a vacuum pressure of at least about 10 −3 torr surrounding the probe tip and the substrate;
applying a bias voltage between the probe tip and the substrate and thereby establishing a current flow between the substrate and the probe tip via field emissions; and
maintaining the bias voltage for a pulse period, wherein upon establishment of a current density of at least about 600 A/m 2 at that area of the substrate surface that is closest to the probe tip, a structure develops from the surface of the substrate.
2. The method according to claim 1 , wherein the probe tip comprises tungsten.
3. The method according to claim 1 , wherein the probe tip is a carbon nanotube.
4. The method according to claim 3 , wherein the carbon nanotube is a multiwalled carbon nanotube.
5. The method according to claim 1 , wherein the substrate comprises silicon.
6. The method according to claim 1 , wherein the semiconducting material is a doped semiconducting material.
7. The method according to claim 1 , wherein the substrate is a multilayer substrate.
8. The method according to claim 7 , wherein at least one layer of the substrate comprises a polymer.
9. The method according to claim 8 , wherein the polymer is a conductive polymer.
10. The method according to claim 8 , wherein the polymer is polymethyl methacrylate.
11. The method according to claim 7 , wherein at least one layer of the substrate comprises a metal.
12. The method according to claim 11 , wherein the metal is silver or gold.
13. The method according to claim 1 , wherein the voltage is between about 100 and about 1000 volts.
14. The method according to claim 1 , wherein the pulse period is less than about 200 seconds.
15. The method according to claim 1 , wherein the structure has an aspect ratio of greater than about 1.
16. The method according to claim 1 , wherein multiple structures develop from the surface of the substrate.
17. A device for forming a pattern element on a substrate, the device comprising:
a probe including a probe tip, the probe tip comprising an at least semiconductive material, the probe tip defining a tip diameter of less than about 500 nm;
a power supply connectable to the probe tip;
a stage, wherein the probe tip and the stage are locatable with respect to one another such that a substrate held on the stage can be held at a distance from the probe tip with the upper surface of the substrate less than about 5 μm from the probe tip; and
an enclosure, wherein the probe tip and the stage are within the enclosure.
18. The device of claim 17 , wherein the probe tip is a carbon nanotube.
19. The device of claim 18 , wherein the carbon nanotube is a multiwalled carbon nanotube.
20. The device of claim 17 , further comprising a cantilever arm, wherein the probe tip is attached to the cantilever arm.
21. The device of claim 17 , the device comprising multiple probe tips.
22. The device of claim 21 , wherein the probe tips are at a distance from one another such that electron emissions from adjacent probe tips interfere with one another.