Pump-Power Dependence of Coherent Acoustic Phonon Frequencies in Colloidal CdSe/CdS Core/Shell Nanoplatelets.
basic_science · Level V
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- Record sourced from PubMed, PMID 28437116.
- Also identified by DOI 10.1021/acs.nanolett.7b01394.
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Abstract
Femtosecond optical pump-probe spectroscopy resolves hitherto unobserved coherent acoustic phonons in colloidal CdSe/CdS core/shell nanoplatelets (NPLs). With increasing pump fluence, the frequency of the in-plane acoustic mode increases from 5.2 to 10.7 cm<sup>-1</sup>, whereas the frequency of the out-of-plane mode remains at ∼20 cm<sup>-1</sup>. Analysis of the oscillation phases suggests that the coherent acoustic phonon generation mechanism transitions from displacive excitation to subpicosecond Auger hole trapping with increasing pump fluence. The measurements yield Huang-Rhys parameters of ∼10<sup>-2</sup> for both acoustic modes. The weak electron-phonon coupling strengths favor the application of NPLs in optoelectronics.