Synthesis of Cabon Nano Tubes and other Nanostructures and their Filed Emission Studies

Abstract

Discovered in 1991, carbon nanotubes (CNTs) have reached the forefront of many industrial research projects. Carbon nanotubes are tubular graphene layers with remarkable mechanical, chemical, thermal and electrical properties, which make them useful in various applications. Depending upon their structure CNTs are of two types i.e. single walled carbon nanotube (SWCNT) and multiwalled carbon nanotube (MWCNT). The nucleation and growth of vertically aligned MWCNT deposited on p-Si substrate by microwave plasma enhanced chemical vapour deposition (MPECVD) process have been carried out. Several characterization techniques such as: scanning electron microscopy, transmission electron microscopy, high resolution transmission electron microscopy, energy dispersive spectroscopy, Raman spectroscopy and glancing angle X-ray diffraction were used for characterization of carbon nanostructures. Various parameters were found to affect the growth and microstructures of nanostructured carbon films like: gas flow ratio, deposition time and cocatalyst thickness. Carbon nanowalls were deposited using Ag-Fe coated Si substrates. Continuous decrease in density and increase in size of carbon nanowalls with increase in growth time was observed. Field emission characteristics of different CNTs and CNWs carried out using a diode configured field emission system. The threshold field and field enhancement factor were determined from the current density vs. electric field and Fowler-Nordheim plots for different samples. It was found that Ag-Fe deposited films have better emission properties as compared to CNT film deposited on Fe. CNWs also have good emission characteristics. CNWs deposited for higher time were found as better emitters.