Tatung Company (Taipei, TW) is the latest company to patent (U.S 7,641,884) a method for fabricating carbon nanotubes. The carbon nanotubes can easily separate from each other without the problem of non-uniformity, thanks to microscale carbon carrier, according to inventors Jian-Min Jeng, Wen-Ching Shih, Ming-Hung Tsai and Jyi-Tsong Lo. Separation of carbon nanotubes can be an expensive and time consuming process and is a major expense in their production.
U.S 7,641,884, FIG. 8 is an SEM photograph of carbon nanotubes grown by Tatung’s method. Tatung is a major computer and appliance manufacturer in Taiwan.
As shown in FIG. 1, which is a schematic flow chart showing Tatung's preparation process for carbon nanotube product. First a carbon micro carrier solution and a clean silicon substrate (step 110) are provided. Here, the carbon micro carrier solution is prepared from mixing an ethylene cellulose solution and a carbon micro carrier solute; the impurities on the silicon substrate are cleaned by de-ionized water. The carbon micro carrier is graphite, the size of which is in a micron scale size (e.g. the size in a range of 0.1 micrometer to several micrometers), but in the other preferably embodiments, the carbon micro carrier can be other materials having carbon atoms, also the size thereof can be greater than that of the present embodiment.
Referring to FIG. 1, the carbon micro carrier is then uniformly provided on the silicon substrate (step 120). The step here uses a spin-coater to drop the prepared carbon micro carrier solution on the silicon substrate and spin-coat the prepared carbon micro carrier solution uniformly on the cleaned silicon substrate. There is no limit on the coating equipment (e.g. spin-coater), other devices also can be used to provide the carbon micro carrier solution on the silicon substrate.
Then, heat-treatment is provided on the spin-coated silicon substrate to remove the solvent of the carbon micro carrier solution, wherein the solvent here is ethylene cellulose (step 130). In the present embodiment, the spin-coated silicon substrate is heated to 360.about.500.degree. C. in order to remove the solvent of the carbon micro carrier solution and keep the carbon micro carrier on the silicon substrate. However, in the other embodiments, the temperature depends upon the content of the carbon micro carrier solution. Next, a plurality of carbon nano particles is formed on the carbon micro carrier by a first gas (step 140). The first gas can be in a molecular state or in a plasma state. If the first gas is in a molecular state, it can be any carbon-containing gas, which is provided from reaction caused by heat treatment applied to the carbon atomThereafter, the silicon substrate 1 is placed in a chamber and a second gas is filling-in to produce a plurality of carbon nanotubes (step 150).
