The Effect of Hot Electrons on the Conductivity of Carbon Nanotubes

Abstract

The effect of hot electrons on the conductivity of undoped single walled achiral carbon nanotubes (CNTs) under the influences of applied de field and dc-ac driven fields along the tube axis are theoretically considered. Semiclassical approach was adopted to solve Boltzmann’s transport equation with and without the presence of the hot electrons source to derive the current densities. Plots of the normalized current density (/z) versus applied de field ( Ez) with and without hot electrons reveal a negative differential conductivity (NDC) at strong electric fields. Also, NDC is observed for plots of Jz versus de field of simultaneously applied dc-ac driven fields in quasi-static state (i. e. cot ≪ 1, where co and t are frequency of ac field, and relaxation time respectively) with and without hot electrons. With strong enough axial injection of the hot electrons in either case, there is an upturn in the normalized current density resulting in a switch from NDC to positive differential conductivity (PDC). The upturn in normalized current density occurs near 50 kV/cm and 75 kV/cm for a zigzag CNT and an armchair CNT, respectively in the case when de field is used while near 75 kV/cm and 140 kV/cm for a zigzag CNT and an armchair CNT, respectively when dc-ac driven fields in quasi-static state replaced the de field. In this region of PDC in each case, the unwanted domain instability usually associated with NDC can be suppressed, suggesting a potential generation at low and high (room) temperatures of terahertz radiations which have enormous promising applications in very different areas of science and technology.