Joydip Sengupta — Page 2

arXiv2019

Growth temperature dependence of partially Fe filled MWCNT using chemical vapor deposition

This investigation deals with the effect of growth temperature on the growth behavior of Fe filled multiwalled carbon nanotubes (MWCNTs). Carbon nanotube (CNT) synthesis was carried out in a thermal chemical vapor deposition (CVD) reactor in the temperature range 650 to 950 1C using propane as the carbon source, Fe as the catalyst material, and Si as the catalyst support. Atomic force microscopy (AFM) analysis of the catalyst exhibits that at elevated temperature clusters of catalyst coalesce and form macroscopic islands. Field emission scanning electron microscopy (FESEM) results show that with increased growth temperature the average diameter of the nanotubes increases but their density decreases. High-resolution transmission electron microscopy (HRTEM) studies suggest that the nanotubes have multi-walled structure with partial Fe filling for all growth temperatures. The X-ray diffraction (XRD) pattern of the grown materials indicates that they are graphitic in nature. The characterization of nanotubes by Raman spectroscopy reveals that the optimized growth temperature for Fe filled CNTs is 850 1C, in terms of quality. A simple model for the growth of Fe filled carbon nanotubes is proposed.

cond-mat.mtrl-sci↗

arXiv2018

Growth and Characterization of Multi-Walled Carbon Nanotubes using Chemical Vapor Deposition

In this study, the synthesis of multi-walled carbon nanotubes (MWCNTs) was carried out by chemical vapor deposition (CVD) using propane as the carbon source and Si as the catalyst support. The effect of CVD process variables such as temperature, choice of catalyst, etc on the growth behavior of nanotubes has been examined to understand the catalytic growth of CNTs. The transition metal catalysts, Fe and Ni, were used in both elemental metal form and in a metal complex form. In the case of elemental metal catalysts, the respective metals were deposited over the Si substrate using thermal evaporation following which nanotubes were synthesized by means of CVD. Subsequent studies of the synthesized carbon nanostructures employing elemental metal catalysts revealed a significant influence of the temperature and the catalyst material on the structure of CNTs. The CNTs synthesized using Ni catalyst were bamboo-like whereas the CNTs developed employing Fe catalyst were straight tubes with partial metal filling. Consequently, growth models for the different growth mechanisms have been proposed. Certain limitations of the above process have been overcome by employing spin-coating of a metal complex catalyst material on the Si substrate. The CVD synthesis of nanotubes using metal complex catalysts always resulted in partially catalyst filled CNTs. More importantly, the metal complex catalyst could be easily patterned on the Si substrate using spin-coating and photolithography, which resulted in site selective growth of partially catalyst filled MWCNTs. Since the entire process of site selective growth is suitable for conventional device fabrication, this method is a promising and practical pathway for large-scale fabrication of several magnetic material filled CNT-based devices.

physics.app-ph↗