Self-sustained acoustoelectric oscillations in fluorine-doped carbon nanotubes under strong electric fields

Abstract: Herein, we report on self-sustaining acoustoelectric direct current oscillations in fluorine-doped single-walled carbon nanotubes stimulated by a strong internal electric field. The study is carried out in the hypersound regime, where carrier transport is confined to the lowest electronic miniband, leading to enhanced nonlinear and non-monotonic acoustoelectric current response. The carrier dynamics predicted by the model are consistent with experimentally observed oscillatory acoustoelectric current in a graphene-based acoustoelectric switch. The oscillatory behavior is shown to originate from spatial charge instabilities and field-induced Bloch-like carrier dynamics, occurring in the absence of an external resonator. The resulting non-uniform space-charge distribution, together with Bloch-reflected carrier motion, is identified as the dominant mechanism responsible for terahertz radiation generation. In addition, the dynamic interplay between acoustic phonons and charge carriers suggests the possibility of suppressing electric domain formation and realizing acoustic Bloch gain. These results demonstrate that fluorine-doped single-walled carbon nanotubes can operate efficiently at elevated temperatures and are promising candidates for high-frequency electronic and optoelectronic applications extending into the submillimeter-wave regime.