Researchers who came from Shanghai Institute of Optics and Fine Mechanics (SIOM), Chinese Academy of Sciences (CAS), have discovered that ultrafast disorder-assisted optical-acoustic phonon interaction plays a pivotal role in ultrafast terahertz conductivity relaxation. The related result was published in the Journal of Physical Chemistry C on January 7, 2022.
Graphene, which possesses massless high mobility Dirac Fermions for high efficiency photoconversion devices, has driven broad attention in their optoelectronic applications. The ultrafast electron-phonon interaction at low energy regions has driven research interest in recent years.
For the sake of clarifying the ultrafast photoconductivity cooling process in Chemical Vapor Deposition (CVD) graphene in several picoseconds, researchers used the ultrafast mid-infrared pulse pump Terahertz probe technique to study the optical phonon-acoustic phonon interaction process. The competition between the disorders assisted defect scattering and the electron-phonon coupling process in the cooling process of the graphene terahertz dynamics is systematically studied and disentangled. The research group verify experimentally that the ultrafast disorder assisted phonon-phonon interaction would play the key role in the ultrafast thermal relaxation of the terahertz dynamics.
Researchers proved that the ultrafast photoconductivity cooling process in CVD graphene in several picoseconds is mainly due to the disorder-assisted super collision process.
Furthermore, the cooling process features robustness which is independent of the pump wavelength and external temperature.
The above results broaden the research ideal of the energy transfer, hot electron extraction, and phonon recycling of graphene-based heterojunctions and can facilitate the improvement of CVD graphene-based nano-optoelectronic devices.
This work is supported by the National Natural Science Foundation of China, the National Key R&D Program of China, and CAS Interdisciplinary Innovation Team.