Structural modifications and enhanced Raman scattering from multiwalled carbon nanotubes grown on titanium coated silicon single crystals

Multiwalled carbon nanotubes (MWCNTs) were grown on 10 nm iron (Fe) film by microwave plasma enhanced chemical vapor deposition using titanium (Ti) film as an interlayer. The Ti interlayer of thickness 5 nm-20 nm was sandwiched between Fe and silicon (Si) using thermal evaporation. Enhanced Raman response was observed in MWCNTs with increasing Ti interlayer thickness. This was related with the plasmonic effects occurring at the interface of the CNTs and the metallic support in a three layer system (Ti-Fe-CNTs). The increase in the G mode optical strength is attributed to surface enhanced resonance Raman scattering. Moreover, the increase in the D-mode and 2D-mode intensity is explained on the basis of double resonance effects. The crystallinity in the samples was calculated using ID/IG ratio. It was found that that ID/IG ratio decreases in three layer system with increasing Ti interlayer thickness as compared to a two layer (Fe-CNTs) system as reported earlier.