Self-oriented bundles of carbon nanotubes and method of making same

US6232706A · kind A · utility

Assignee

• The Board of Trustees of the Leland Stanford Junior University · US

Inventors

• Hongjie Dai · Sunnyvale, US
• Shoushan Fan · Beijing, CN
• Michael Chapline · Alamo, US
• Nathan Franklin · San Mateo, US
• Thomas Tombler · Goleta, US

Key dates

• Filing date: Nov 12, 1998
• Grant date: May 15, 2001
• Expiry date: Nov 12, 2018

Classification

• Technology area (CPC Y): Emerging Cross-Sectional Technologies
• CPC primary: Y10S977/939
• WIPO field: Micro-structural and nano-technology
• WIPO sector: Chemistry

Abstract

A field emission device having bundles of aligned parallel carbon nanotubes on a substrate. The carbon nanotubes are oriented perpendicular to the substrate. The carbon nanotube bundles may be up to 300 microns tall, for example. The bundles of carbon nanotubes extend only from regions of the substrate patterned with a catalyst material. Preferably, the catalyst material is iron oxide. The substrate is preferably porous silicon, as this produces the highest quality, most well-aligned nanotubes. Smooth, nonporous silicon or quartz can also be used as the substrate. The method of the invention starts with forming a porous layer on a silicon substrate by electrochemical etching. Then, a thin layer of iron is deposited on the porous layer in patterned regions. The iron is then oxidized into iron oxide, and then the substrate is exposed to ethylene gas at elevated temperature. The iron oxide catalyzes the formation of bundles of aligned parallel carbon nanotubes which grow perpendicular to the substrate surface. The height of the nanotube bundles above the substrate is determined by the duration of the catalysis step. The nanotube bundles only grow from the patterned regions.