Metal Induced Intershell Coupling and Conductance Enhancement in Multiwalled Carbon Nanotubes

N. Kulshrestha, A. Misra, R. Bajpai, S. Roy, D.S. Misra
Indian Institute of Technology Bombay, IN

Keywords: multiwalled carbon nanotubes, intershell coupling, I-V characteristics, density of states


Using two different metal (platinum and Tungsten) depositions on the individual multiwalled carbon nanotubes bridging the spacing between two gold electrodes, we segregate the contributions of change in nanotubes inherent properties and contact-improvement in total conductance enhancement caused by metal deposition. In these experiments, the metals were deposited precisely at the desired locations on the tubes using gas injection system available in the Raith150-Two direct write setup with 3 KeV electron beam induced deposition using organometallic precursor trimethyl-methylcyclopentadienyl-platinum (for Pt) and tungsten hexacarbonyl (for W). Typical increment up to 140% to 540% in conductance has been observed after Pt and W metal depositions on the MWNTs. The change in conductance is explained in terms of change in the density of states at Fermi level, due to charge transfer between metal atoms and nanotube as well as by radial stress created on the tube. HRTEM investigation of the metal deposited tubes suggests that metal atoms diffuse within the deep shells of the tube causing increased intershell interactions and hence improved electrical conductance.