Quantum Treatments of Electronic Characteristics of Carbon Nanotubes via the Density Functional Green's Function Method

Density functional non-equilibrium green's function method is used to investigate the switching behaviour of various types of single walled carbon nanotubes (SWCNTs). Electron transport through both the defective and defect-free SWCNT molecular wires sandwiched between an Al (1 0 0) substrate and a monoatomic Al scanning tunneling microscope (STM) tip has been examined. Our first-principles calculations show that current intensity has the same values for all considered conformations for the defect-free SWCNTs and hence no significant difference in conductance was occurred by the STM tip displacement. However, when the tip moves laterally over the different configurations of the defective tube thus surprisingly, this simple molecular device switches between a strongly and a weakly conducting state. In addition, a realistic theory of its switching behaivour has been investigated by the projection of the density of states and transmission coefficients of the two-probe system.