ROLE OF HETEROATOMS ON CYLINDRICAL CNT SURFACE WITH HEMISPHERICAL TIP

Abstract

This project puts forward a theoretical model to examine the growth of the carbon nanotube (CNT) on top of catalyst substrate surface subjected to reactive plasma. Various processes have been considered in this model, such as the charging rate of the CNT, kinetics of electron, ions and neutral atoms. Also, the growth of the CNT due to diffusion and accumulation of ions on the catalyst nanoparticles is taken into account. For characteristic glow discharge plasma, numerical calculation on the impact of ion density, temperature and the substrate bias over the growth rate of carbon nanotubes has been carried out. Through it, the change in radius, height and the number density of hydrocarbon ions with time has been shown. Comparison has been made between the two doped gases that are nitrogen and boron, and also with the undoped condition. Along with it, the change in the concentration of the hydrocarbon ions in plasma along the time is computed for three conditions (undoped, nitrogen doped and boron doped). The CNT considered here has hemi-spherical tip as it provides better field emission which distinguish this work from the work of Tewari and Sharma [31]. Different gases have been used in the process. The mixture of gases includes hydrocarbon (CH3), hydrogen (H2), nitrogen (N2) and boron (B). It is obtained that the height of CNT increments with the number density of carbon ions and radius of CNT reduces with hydrogen ion density. The nitrogen and boron acts as doping elements here. It is found that nitrogen obstruct both the height as well as radius of CNT, whereas in boron, both the radius and height increases in comparison to the nitrogen doping. The present work can serve to the better comprehension of procedure parameters amid growth of hemispherical tip CNT with cylindrical surface by a Plasma Enhanced Chemical Vapor Deposition (PECVD) method.