Category: 2005

Structural control of vertically aligned multiwalled carbon nanotubes by radio-frequency plasmas

Renato Pinto Reveggino

PECVD_CNTs_APL2005

Carbon nanotubes CNTs are among the important materials for the advancement of future nanoscience and nano-technology. Recently, vertically aligned multiwalled carbon nanotubes VA-MWCNTs have gained additional attention for innovative applications, such as nanotubes antennas,1vertical transistors,2,3 and vertical biosensors.4 Ideally, these applications require VA-MWCNTs to be grown at desired patterns. Plasma-enhanced chemical vapor deposition PECVD is the only technique for growing individual VA-MWCNTs at desired locations. However, the graphitic order of these VA-MWCNTs is inferior to the multiwall CNTs grown by arc discharge5 and thermal chemical vapordeposition.6–8 This has been a long-standing issue for realis-tic uses of VA-MWCNTs in applications, such as electron field emission devices.9–13

 

Vertically Aligned Carbon Nanotubes as the Sputter Resist in Space Propulsive Systems

Renato Pinto Reveggino

CNTSpacePropulsionMRS2005

Two-types of vertically aligned multi-walled carbon nanotubes (VA-MWNTs) are

evaluated as the protective coatings against ion erosion in electric propulsion systems. A

series of experiments have been conducted to understand the erosion rate and erosion

mechanism of these VA-MWNTs. These experiments were carried out with Xe

propellant at an ion current density of 5 mA/cm2. We found that the erosion rates of both

types of VA-MWNTs were changing with time. Such a nonlinear erosion process is

explained according to a possible erosion mechanism.

High-density vertically aligned multiwalled carbon nanotubes with tubular structures

Renato Pinto Reveggino

CNTs-APL2005

Ammonia sNH3d gas was thought to be essential for the growth of vertically aligned multiwalled

carbon nanotubes sVA-MWCNTsd and led to the formation of bamboo-like structures. Here, we

show that VA-MWCNTs with ideal tubular structures can be grown on substrates by various mixed

gases with or without NH3 gas. The growth of these VA-MWCNTs is guided by a growth model that

combined the dissociative adsorption of acetylene molecules sC2H2d and the successive

vapor-liquid-solid growth mechanism. Results indicate that the key factor for growing these

VA-MWCNTs is a balance between the decomposition rate of the C2H2 molecules on the iron

catalyst and the subsequent diffusion and segregation rates of carbon.

© 2005 American Institute of Physics. fDOI: 10.1063/1.1952575g

A Dual-RF-Plasma Approach for Controlling the Graphitic Order and Diameters of Vertically-Alligned Multiwall Carbon Nanotubes

Renato Pinto Reveggino

CNT_MRS2005

Plasma enhanced chemical vapor deposition (PECVD) is a unique technique for growing

vertically-aligned multiwall carbon nanotubes (VA-MWNTs) at controllable tube densities. This

technique is of considerable importance for low temperature growth of VA-MWNTs at desired

locations. However, the graphitic order of these MWNTs is inferior to those grown by laser

ablation, arc discharge, and thermal CVD techniques. Previously, these VA-MWNTs were

grown by a one-plasma approach (DC, microwave etc), either for gas decomposition or substrate

biasing. Here, we describe a dual-RF plasma enhanced CVD (dual-RF-PECVD) technique that

offers unique capability for controlling the graphitic order and diameters of VA-MWNTs.