Metallization of carbon nanotubes for field emission applications

Abstract

The present invention is directed towards metallized carbon nanotubes, methods for making metallized carbon nanotubes using an electroless plating technique, methods for dispensing metallized carbon nanotubes onto a substrate. The present invention is also directed towards cold cathode field emitting materials comprising metallized carbon nanotubes, and methods of using metallized carbon nanotubes as cold cathode field emitters.

Description

[0001] The present application claims priority to the following U.S. Provisional Patent Application, Serial No. 60 / 417,246.[0002] The present invention relates in general to nanostructured materials, and in particular, to using modified carbon nanotubes for field emission applications.BACKGROUND INFORMATION[0003] Carbon nanotubes (CNTs) are currently being investigated for use as cold electron sources in a variety of applications. These include displays, microwave sources, x-ray tubes, etc. For CNTs to be used as a cold cathode, they must be placed on a conductive surface (conductive substrate or conductive film on a non-conductive substrate). This has led some to place catalysts on the substrate surface and grow the carbon nanotubes in situ using CVD techniques (Kim et al., J. Appl. Phys., 90(5), 2591 (2001)). However, this has several draw-backs. This technique typically grows multi-wall carbon nanotubes (MWNTs). However, MWNTs have poorer field emission quality compared to single...

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Problems solved by technology

However, this has several draw-backs.

However, MWNTs have poorer field emission quality compared to single-wall carbon nanotubes (SWNTs).

The substrate is subjected to high temperature, typically above 600.degree. C., limiting the substrates that can be used.

Uniformity is difficult to achieve because of the high temperature growth processes required.

As a result, the manufacture of cathodes using this process will be very expensive due to the number and complexity of post-processing steps needed to generate a material capable of producing the desired level of field emission.

Third, uniform deposition over large area substrates is far more feasable using currently-available, low-cost equipment.

Current dispensing processes, however, have their disadvantages.

These factors limit the performance of the CNT material.

These "activation" process steps, however, can add cost to the product and may lead to non-uniform performance.

Yet another disadvantage of current dispensing techniques is that the dispensed CNT fibers may not have sufficiently good contact to the substrate or the substrate's conductive layer such that this impedes their ability to supply the electrons needed for field emission.

This method has the inherent aforementioned disadvantages of growing CNTs on the substrate.

Furthermore, were the CNT fibers to be dispensed onto the substrate and then coated, the problems of separating the CNT fibers for improved emission would still remain.

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