Patent ID: 8609061

Claim:
A method for forming a carbon nanotube array, the method comprising steps of: (a) providing a substrate with a catalyst layer on the substrate, and placing the substrate into a reaction chamber; (b) supplying at least two kinds of carbon source gases, each carbon source gas comprising a single carbon isotope, wherein the carbon isotopes of the at least two kinds of carbon source gases are different from each other; (c) introducing the at least two kinds of carbon source gases into the reaction chamber of the reaction device simultaneously; and (d) heating the whole catalyst layer to a first temperature to react one of the carbon source gases under the first temperature, and simultaneously controlling at least one part area of the catalyst layer to a second temperature higher than the first temperature, whereby a second isotope-doped carbon nanotube sub-array is formed on the at least one part area, and a first isotope-doped carbon nanotube sub-array is formed on other areas of the catalyst layer other than the at least one part area, the second isotope-doped carbon nanotube sub-array being composed of at least two kinds of carbon isotopes.