Herein, we present a tunable axial power factor (Pzz) in a nondegenerate fluorine-doped single-walled carbon nanotube (FSWCNT) using a tractable analytical approach. We derived the expressions for the electrical conductivity (σ), thermopower (α), and power factor (P) as a function of temperature. Additionally, we investigated the influence of doping concentration (no), constant electric field (Eo), and overlapping integrals (Δs and Δz) on their behavior. The intensity of the axial power factor (Pzz) and the operational temperature range can be tuned using the constant electric field, doping (carrier), and overlapping integrals, respectively. Applying the temperature field to the FSWCNT induces high-frequency carrier dynamics that critically depend on the magnitude of the temperature gradient. There exist two dynamic regimes that depend on the temperature gradient and carrier’s initial position. The carrier drifts through the FSWCNT and is allowed to perform drifting periodic orbits (in THz frequencies), resulting in the resonant enhancement of Pzz. Alternatively, inducing Bloch-like oscillations (in THz frequencies) cause ultra-high negative differential velocity without domain formation using an adequate temperature field. Moreover, we compare the Pzz of the FSWCNT to that of the superlattice (SL) (PzzSL), which shows that the Pzz of the FSWCNT is 8 orders of magnitude greater than that of the SL. It is worth noting that the large Pzz obtained and the ability to tune the FSWCNT to operate at high temperatures make the FSWCNT a potential candidate for thermoelectric applications.
Acoustoelectric effect (AE) in a non-degenerate Fluorine modified single walled carbon nanotube (FSWCNT) semiconductor is studied theoretically using the Boltzmann's transport equation. The study is done in the hypersound regime i.e. 1 q , where q is the acoustic phonon wavenumber and is the electron mean free path. The results obtained are compared with that of undoped single walled carbon nanotube (SWCNT). The AE current density for FSWCNT is observed to be four orders of magnitude smaller than that of undoped SWCNT with increasing temperature, that is FSWCNT SWCNT z z j j . This is because the electron-phonon interactions in SWCNT are stronger than FSWCNT. Thus, there are more intra-mini-band electrons interacting with the acoustic phonons to generate a higher AE current in SWCNT than in FSWCNT. This has been observed experimentally, where the electrical resistance of FSWCNT is higher than pristine SWCNT i.e. 20 M R Ω . The study shows the potential for FSWCNT as an ultrasound current source density imaging (UCSDI) and AE hydrophone material. However, FSWCNT offers the potential for room temperature applications of acoustoelectric device but other techniques are needed to reduce the resistance.
The acoustoelectric effect AE in Graphene with degenerate energy dispersion is theoretically studied for hypersound in the regime ql >> 1. At low temperatures (k β T << 1), the non-linear dependence of Acoustoelectric current j/j 0 on the frequency ω q and temperature T are numerically analysed. The obtained graph for j/j 0 against ω q qualitatively agreed with an experimentally obtained results. For j/j 0 versus T , the dependence of Acoustoelectric current in Graphene was found to manifest at low temperatures.
We studied theoretically the absorption of acoustic phonons in the hypersound regime in Fluorine modified Carbon Nanotube (F-CNT) Γ F −CN T q and compared it to that of undoped Single Walled Nanotube (SWNT) Γ SW N T q .Per the numerical analysis, the F-CNT showed less absorption to that of|. This is due to the fact that Fluorine is highly electronegative and weakens the walls of the SWNT. Thus, the πelectrons 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 isClearly, the ratio decreases as the temperature increases.
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