Patent ID: 7704547

Claim:
A method for control of growth density of carbon nanotubes on a substrate, the method comprising: providing a substrate, with at least one surface coated with a catalyst that enhances growth of carbon nanotubes (“CNTs”) thereon; providing a nominal or average growth density value D 0 for carbon nanotubes (“CNTs”) grown in a nominal temperature range, T 1 ≦T≦T 2 , and a desired CNT growth density value D 1 , with D 1 ≦D 0 ; representing a logarithm of a ratio of average growth density value D 0 divided by desired growth density value D 1 as a value log A {D 0 /D 1 }=X+Y, where X is approximately an integer and Y=log A {D 0 /D 1 }−X has a magnitude |Y| no greater than about 1, where A is a selected logarithm base value at least equal to about 2; imposing an electrical field having a value E=E b adjacent to the catalyst-coated substrate surface, where the field is oriented substantially perpendicular to the catalyst-coated substrate surface and adjacent to the substrate surface, for which imposition of the electrical field E b , and growth of the CNTs in the nominal temperature range, T 1 ≦T≦T 2 , will produce CNTs having an average growth density of D 1 ′≈D 0 ·A −X ; providing at least one feed gas comprising C m1 H n1 , where m 1 ≧1 and n 1 ≧2, adjacent to the substrate, where the at least one feed gas is heated to a temperature T within an adjusted temperature range, T L ≦T≦T U , having a lower temperature value T L and an upper temperature range T U that is at least equal to T L , for which growth of CNTs in the adjusted temperature range with no electrical field imposed will produce CNTs having an average growth density of D 1 ″≈D 0 ·A −Y ; and transporting the heated feed gas across the catalyst-coated surface, allowing at least a portion of the heated feed gas to decompose to provide two or more C particles, and allowing at least a portion of the C particles to form an array of CNTs having an average CNT density of about D 1 in a selected region R 1 of the catalyst-coated substrate surface.