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Original Publication Date: 2001-Apr-30
Included in the Prior Art Database: 2001-Apr-30
Document File: 2 page(s) / 6K

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Justin Lewenstein: AUTHOR [+5]



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by Justin Lewenstein, Chan-Long Shieh, Timothy Burgin, Thomas Harvey III, Larry Nagahara and Raymond Tsui

The use of molecular scale components (MSCs), such as carbon nanotubes (CNTs), as building blocks to create nano-scale structures with useful electrical functionality has been investigated. CNTs are particularly promising for building ultra-small electronic devices due to their nm-scale diameters as well as exceptional electrical and mechanical properties. CNTs may be either metallic or semiconducting depending on their diameter and chirality. Metallic CNTs have very high current carrying capacities (107 A/cm2) and may serve as nano-scale interconnects.

CNTs have also been used as the active component of nano-scale devices such as single-electron transistors and room temperature field effect transistors.

In order to take advantage of the unique properties of CNTs it is necessary to control their location and orientation on a surface. For bulk produced material, a means of selectively depositing the CNTs from a liquid suspension is required. Previous techniques have involved the random deposition of CNTs on to surfaces and their repositioning using an AFM tip. This "brute force" method is time consuming and does not allow for the selective placement of large quantities of CNTs in parallel.

A simple, inexpensive and reliable process is needed to control the selective alignment and placement of MSCs. Patterned self-assembled monolayers with differing affinities for CNTs have been used to direct their deposition on a surface. In one example, patterns were formed by the e-beam degradation of a surface treated with hexamethyldisilazane.

The exposed areas were then treated with aminopropyltriethoxysilane (APS) to create regions with a high affinity for CNTs.

However, this approach does not provide selectivity high enough to ensure that the CNTs are positioned only at their intended locations.

It has been demonstrated that the selective placement from a bulk CNT suspension onto lithographically patterned areas with a high affinity for CNTs. The patterns are prepared in a conventional e-beam resist, and the exposed regions are treated with APS to increase their affinity for CNTs.

Initial attempts at selective placement have shown resist degradation caused by the CNT suspension medium. However, by taking steps to make the resist more chemically robust, aminosilanization and CNT placement can be performed with the resist still present.

A high degree of selectivity in CNT placement is achieved by utilizing well-established lithographic and microelectronic fabrication procedures, and using the resist as the masking element.

CNTs deposited on the masked areas of the substrate are removed during the resist strip.

The diagram below shows the steps used for the selective placement of MSCs such as CNTs on a che...