Effect of a silicon oxide substrate on the electronic properties and the electrical conductivity of mono- and bilayer films of armchair single-wall carbon nanotubes: a quantum-mechanical study

The electrical properties of mono- and bilayer single-wall carbon nanotubes (SWCNTs) disposed on silicon oxide SiO$_2$ substrates have been studied. The substrate is a silicon dioxide crystal film with space group P4$_2$/mnm with surface (100). As SWCNTs, armchair nanotubes of subnanometer diameter (4,4) and nanometer diameter (7,7) are considered. The nanotube diameter is found to mainly determine the electronic properties of the film on the substrate. Thin tubes (4,4) formed into a bilayer film (with mutually perpendicular orientation of each other) have the lowest electrical resistance. The substrate influences only slightly on the electronic properties of similar film. The films with tubes of larger diameter are characterized by a higher electrical resistance. It is found that the SWCNT–substrate contact surface is of a crucial importance.