Electron emitting composite based on regulated nano-structures and a cold electron source using the composite

Abstract

A field emission electron source includes a substrate, a first conductive electrode terminated to provide electrons, an emitting composite layer for emitting electrons, and a second electrode insulated from the emitter layer and terminated to extract electrons through vacuum space. The emitting composite layer lies between and parallel to the said first and the second electrodes, and comprises nano-structures embedded in a solid matrix. One end of the nano-structures is truncated and exposed at the surface of the emitter layer so that both the length and the apex of the nano-structure are regulated and the exposed nano-tips are kept substantially the same distance from the gate electrode. The embedding material is chosen to form triple junctions with the exposed tip to further enhance the field.

Description

CROSS REFERENCE TO RELATED APPLICATIONS [0001] This application claims priority to and incorporates by reference each of the following applications: [0002] U.S. Provisional Application titled ELECTRON SOURCE BASED ON REGULATED NANO-STRUCTURED MATERIALS, Ser. No. 60 / 457,210, filed Mar. 24, 2003; [0003] U.S. Provisional Application titled COLD ELECTRON SOURCE BASED ON REGULATED NANO-STRUCTURED MATERIALS, Ser. No. 60 / 491,570, filed Jul. 30, 2003; and [0004] U.S. Provisional Application titled ELECTRON EMITTING COMPOSITE BASED ON REGULATED NANO-STRUCTURES AND A COLD ELECTRON SOURCE USING THE COMPOSITE, Ser. No. 60 / 521,135, filed Feb. 24, 2004. [0005] This application also claims the benefit of U.S. patent application Ser. No. 10 / 807,890, titled “ELECTRON EMITTING COMPOSITE BASED ON REGULATED NANO-STRUCTURES AND A COLD ELECTRON SOURCE USING THE COMPOSITE,” filed Mar. 24, 2004.BACKGROUND OF INVENTION [0006] The present invention relates generally to the emission of electrons from nano-str...

AI Technical Summary

Benefits of technology

The present invention provides an electron source using nano-structures as emitter that overcomes the challenges of the prior art, such as limited field enhancement, variations in tip-to-gate distance and tip apex, and difficulty in fabrication. The invention also allows for a more consistent and stable field enhancement, enabling many more desirable nano-structures to be used as field emitters. The electron source is easy to gated, has high emission site and current density, is substantially collimated, and has a long lifetime and steady performance. The invention also provides an insulator layer that is easy to fabricate and has a high yield. The conductive nano-structures can be embedded in a conductive matrix or insulated from each other, and the emitter layer has a surface at which ends of the nano-structures are truncated and exposed for emitting electrons.

Problems solved by technology

The high cost and low yield associated with its fabrication process, and the high susceptibility of the tip to contamination and ion bombardment have effectively prevented this technology from wide application.

As a result, the hope of deriving an electron source of high emission site density from a vertically aligned CNT array has largely unfulfilled.

Two major problems plague these random CNT films.

First, emission is inhomogeneous and often dominated by strong sites so that the emission site density is still relatively low despite of improvement over vertically aligned CNTs.

Second, it is difficult to fabricate a gate electrode on top of these films without degrading their emission properties.

Such a large distance results in high driving voltage, and the emission from underneath the grid goes directly to the grid without contributing to the output current.

The difficulty in accurately and uniformly mounting and maintaining a fine grid over large area with a small gap is another hurdle.

However, the emission performance from these films is worse than when the film is directly grown on the surface.

Such variation, plus the electrostatic screening effect between CNTs in the same gate hole, causes an emission dominated by the ones closer to the gate in each gate hole, and changes the emission threshold field from gate hole to gate hole, resulting in a source of little practical use.

The device still does not address the problem of a varying CNT in its height and aspect ratio in each gate hole and there is little emitter redundancy built in.

Also, due to the large inter-tube spacing, CNT grow thick, reducing the aspect ratio and therefore increasing the driving voltage.

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