Raman spectroscopy study of growth of multiwalled carbon nano-tubes using Plasma Enhanced Chemical vapour depositon

Here, we report the study of growth of CNTs using pulsed DC Plasma Enhanced Chemical Deposition (PECVD) process. Pulsed DC PECVD is employed as it provides enhanced control on arcing and uniformity over large area and thus control on length, diameter and positioning of CNTs. High yields of Multi-Walled Carbon nanotubes with diameters ranging from 40 to 100 nanometers are synthesized by plasma enhanced chemical Vapour deposition system. A layer of Titanium (50 nm) is used as buffer layer and a layer of Nickel (~10 nm) is used as catalyst layer. Effect of Temperature, growth pressure and acetylene (C₂H₂) concentration on the synthesis of CNTs is studied. CNTs are characterized by Secondary Electron Microscopy (SEM) and Raman spectroscopy. Uniform CNTs growth observed at growth temperature 700°C and 800°C .Raman spectroscopy of CNTs shows that the strength of D-band (Defect-induced band) relative to G-band (Graphite-related optical band) decreases as the growth temperature increases which indicates the crystalline, defects free, uniform diameter and length of aligned CNTs. From temperature 700°C to 800°C, Up-shift in D-band indicates the increase in diameter of CNTs while up-shift in G-band may because of chemical doping in tubes. Downshift in G-band.