We studied theoretically the absorption of acoustic phonons in the hypersound regime in Fluorine modified carbon nanotube (F-CNT) Γ q F − CNT and compared it to that of undoped single walled carbon nanotube (SWCNT) Γ q SWCNT . Per the numerical analysis, the F-CNT showed less absorption to that of SWCNT, thus ∣ Γ q F − CNT ∣ < ∣ Γ q SWCNT ∣ . This is due to the fact that Fluorine is highly electronegative and weakens the walls of the SWCNT. Thus, the π -electrons associated with the Fluorine causes less free charge carriers to interact with the phonons and hence changing the metallic properties of the SWCNT to semiconductor by the doping process. From the graphs obtained, the ratio of hypersound absorption in SWCNT to F-CNT at T = 45 K is Γ SWCNT Γ F − CNT ≈ 29 while at T = 55 K , is Γ SWCNT Γ F − CNT ≈ 9 and at T = 65 K , is Γ SWCNT Γ F − CNT ≈ 2 . Clearly, the ratio decreases as the temperature increases.
Part of the book: Phonons in Low Dimensional Structures