Generation and Amplification of Terahertz Radiation in Carbon Nanotubes
  We investigate theoretically the feasibility of generation and amplification of terahertz radiation in aligned achiral carbon nanotubes (zigzag and armchair) in comparison with a superlattice in the presence of a constant (dc) and high-frequency (ac) electric fields. The electric current density expression is derived using the semiclassical Boltzmann transport equation with a constant relaxation time with the electric field applied along the nanotube axis. Our analysis on the current density versus electric field characteristics demonstrates negative differential conductivity at high frequency as well as photon assisted peaks. The characteristic peaks are about an order of magnitude styronger in the carbon nanotubes compared to superlattice. These strong phenomena in carbon nanotubes can be used to obtain domainless amplification of terahertz radiation in carbon nanotubes at room temperature. 
S. S. Abukari, S.Y.Mensah, N. G. Mensah, K. W. Adu, M. Rabiu, K. A.   Dompreh, and A. Twum
cond-mat.mes-hall