Superthin sheets with extraordinary electronic properties can be produced by unrolling tiny carbon tubes. Chemists apply a mixture of sulfuric acid and potassium permanganate. This reagent pries open some of the carbon-carbon bonds, opening a breach in the hexagonal cells. Continued chemical reactions proceed down the tube, opening a pathway along the chicken-wire structure, causing it to unfurl all the way down its length, producing a conductive ribbon that is extraordinarily long and thin. A graphene field-effect transistor, consists of a single ribbon of graphene with one side laid down on a positive electrode, the other laid down on a negative one. A third electrode, or gate, can then modulate the flow of electrons through the ribbon, turning the device into a switch. Although creating graphene sheets using adhesive tape may be a fine laboratory technique, it's hardly practical for mass production. A group at Stanford has used plasma jets to blow the tops off multiwalled carbon nanotubes while protecting the sides of the tubes under a polymer film.
ASJC Scopus subject areas
- Electrical and Electronic Engineering