Selective growth of single-walled carbon nanotubes on textured Si wafer

Abstract

A single-walled carbon nanotube (SWNTs) is formed by rolling a sheet of graphene into a cylinder along an (n,m) lattice vector in the graphene plane . The (n,m) indices determine the diameter and chirality. Depending on the chirality (the chiral angle between hexagons and the tube axis), (SWNTs can be either metals or semiconductors, with band gaps that are relatively large (~0.5 eV for typical diameter of 1.5 ㎚) or small (~10 meV). metallic and semiconducting carbon nanotubes exist in all materials synthesized by arc-discharge, laser ablation, and chemical vapor deposition methods. We have synthesized SWNTs by CVD (Chemical vapor deposition). CVD utilizes acetylene gases for carbon atoms and metal catalyst particles for carbon nanotube growth that takes place at relatively lower temperatures (800℃). We have developed a method to separate metallic from semiconducting SWNTs from environment using etching process. By measuring different SWNTs resonant with the incident laser, and having diameters d t ranging between 0.9 nm and 1.7 nm, we have conclusively determined the dependence of the two most intense G-band and RBM mode features on the nanotube structure. We then present the separated metallic and semiconducting evaluation results of these methods, with emphasis on atomic force microscopy (AFM)-based detection techniques. Finally, the prospects of precise and large-scale measurement of separated metallic and semiconducting in achieving controlled synthesis and understanding growth mechanism of SWNTs.