Publication details
CARBON NANOTUBES SYNTHESIZED BY PLASMA ENHANCED CVD AT ATMOSPHERIC PRESSURE AND THEIR POST-DEPOSITION TREATMENT
| Authors | |
|---|---|
| Year of publication | 2007 |
| Type | Article in Proceedings |
| Conference | New Perspectives of Plasma Science and Technology CD |
| MU Faculty or unit | |
| Citation | |
| Field | Plasma physics |
| Keywords | PECVD; carbon nanotubes; oxidation; SEM |
| Description | Carbon nanotubes (CNTs) were synthesized by plasma enhanced chemical vapor deposition from mixture of argon, methane and hydrogen using microwave plasma torch at atmospheric pressure. Nanotubes grew on a complex substrate system consisting of silicon wafer, buffer layer and thin catalytic iron film. As confirmed by scanning electron microscopy (SEM), this deposition technique produces bundles or ropes of nanotubes covered by crust composed of catalytic particles, amorphous carbon and other impurities such as fullerenes or other carbon nanoparticles. Because many scientific and technological applications, as well as characterization techniques require individual nanotubes a great attention has to be paid to the post-deposition processing of the deposit. The nanotube bundle could be separated by ultrasonication of the deposit in organic or inorganic liquid. Most commonly used liquids are water or ethanol. Both liquids proved to be efficient in removing deposited nanotubes from the substrate, but the bundle separation was not entirely successful as nanotubes in the bundle were hold together by the amorphous carbon crust, as observed by SEM. In order to remove the crust entirely, the deposite can be oxidized in a plasma, in a gas under high temperature or in a liquid. Deposits with different amount of impurities were chosen for thermal oxidation at the temperature of 550 C and studied by SEM before and after treatment. SEM micrographs showed that the oxidation was successful as concerns the impurity removal, but also a great amount of deposited nanotubes has been lost. Oxidation of nanotube deposit in liquid (mixture of H2SO4 and HNO3) did not caused looses and also seemed to be more homogeneous than gas oxidation, but is not convenient for deposits that contain a great amount of single-walled CNTs as these strong acids cause damage to SWNT structure. |