Foster Miller Reveals Mass Production Methods for Cheaper Carbon Nanotube Electronic Devices Via Electrolytic Deposition, "Burn Out" and Lithography

Foster Miller, Inc. (Waltham, MA) inventors reveal carbon nanotube-based electronic devices made by electrolytic deposition and their applications in U.S. Patent 7,632,762.  Thomas Tiano, John Gannon, Charles Carey, Brian Farrell, and Richard Czerw developed a novel method of fabricating single-wall carbon nanotube devices that includes the combination of an electrolytic deposition process, followed by an operation to selectively "burn out" the percolated metallic nanotubes and, thereby, form a semiconducting nanotube-based electronic device.  The devices that can be formed include chemical or biological sensors, carbon nanotube field-effect transistors (CNFETs), tunnel junctions, Schottky junctions, and multi-dimensional nanotube arrays to give only a few examples.

The invention also provides preferred methods of forming a semiconductive device by applying a bias voltage to a carbon nanotube rope. The plurality of metallic single-wall carbon nanotubes are removed (e.g., by application of bias voltage) in an amount sufficient to form the semiconducting device.  The Foster-Wheeler fabrication method provides an efficient, cost-effective process for mass producing nanotube-based electronic devices that is scalable. 

SWNT ropes or single nanotubes can be used to make junctions, by the insertion of a layer of suitable material between the nanotubes. Additionally, a molecular wrap or an insulating layer that is about 10 nm thick forms a tunnel junction. There are many types of devices standard in the microelectronic art that are formed from tunnel junctions. The simplest tunnel junction application is as a two-state logic device that has a low conductivity state at low voltage and a high conductivity state above a voltage threshold level. A high quality oxide layer may be used to implement an FET, within which a voltage on one nanotube depletes or injects electrons into the other nanotube. One nanotube, in this case, is a semiconducting or burnt-out SWNT rope, while the other is a metallic nanotube or SWNT rope that has percolating metallic paths.

Very dense arrays of junctions may be made by use of crossover nanotube junctions, such as crossover nanotube junctions of 2D nanotube array or crossover nanotube junctions of 2D nanotube array. These arrays use the .about.1 micron length nanotubes, in order to interface with control, i.e., input and output lines that are formed by conventional lithography. A crossbar geometry is used to define junctions on a submicron (50 nm) scale.