Absorption of Acoustic Phonons in Fluorinated Carbon Nanotubes with Non-Parabolic, Double Periodic Band

Abstract

We studied theoretically the absorption of acoustic phonons in the hypersound regime in Fluorine modified Carbon Nanotube (F-CNT) $\Gamma_q^{F-CNT}$ and compared it to that of undoped Single Walled Nanotube (SWNT) $\Gamma_q^{SWNT}$. Per the numerical analysis, the F-CNT showed less absorption to that of SWNT thus $\vert\Gamma_q^{F-CNT}\vert < \vert\Gamma_q^{SWNT}\vert $. This is due to the fact that Fluorine is highly electronegative and weakens the walls of the SWNT. Thus, the $\pi$-electrons associated with to the Fluorine which causes less free charge carriers to interact with the phonons and hence changing the metallic properties of the SWNT to semiconductor by the doping process. From the graphs obtained, the ratio of hypersound absorption in SWNT to F-CNT at $T = 45K$ is $\frac{\Gamma_{(SWNT)}}{\Gamma_{(F-CNT)}}\approx 29$ whilst at $T = 55K$, is $\frac{\Gamma_{(SWNT)}}{\Gamma_{(F-CNT)}}\approx 9$ and at $T = 65K$, is $\frac{\Gamma_{(SWNT)}}{\Gamma_{(F-CNT)}}\approx 2$. Clearly, the ratio decreases as the temperature increases.