Pimo He

Model calculation for the field enhancement factor of carbon nanotube

To estimate the apex field enhancement factor associated with carbon nanotube on a planar cathode surface, the simple model of floated sphere between parallel anode and cathode plates was studied. When the anode-cathode distance d is much larger than the height h of carbon nanotube, the field enhancement factor of carbon nanotube was given as the following expression β0=h∕ρ+3.5 with the image method, which is a little than the early work of Miller. Finally, the influence of the anode-cathode distance on the enhancement factor was also discussed and the expression of enhancement factor of carbon nanotube should be modified to be β=h∕ρ+3.5+A(h∕d)3, where A is the constant. This shows a much weaker influence of the relatively smaller anode-cathode distance on the field enhancement factor of carbon nanotube than that estimated earlier. Thus, we can lower the threshold voltage to some extent by the decrease of the anode-cathode distance. The higher aspect ratio of carbon nanotube and the lower anode-cathode di...

Stability and magnetism of tetracyanoethylene adsorbed on substitutionally doped graphene

The stability and magnetism of tetracyanoethylene (TCNE) adsorbed on Si-, B-, and N-doped graphenes are investigated using the spin-polarized density functional theory. TCNE molecules energetically prefer chemisorption on Si-doped graphene, whereas they favor physisorption on B- and N-doped graphenes. The interaction between TCNE molecules and graphene can be improved by doping, which induces a remarkable change in the electronic properties of graphene. The magnetic moment due to the adsorption depends on the adsorption orientation of TCNE and the substitutionally doped atoms. Furthermore, spin density analysis shows that the magnetic moment is located mainly on the TCNE molecule.