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Intersubband Relaxation in CdSe Colloidal Quantum Wells
Benjamin T Diroll1, Richard D Schaller1,2
1Center for Nanoscale Materials, Argonne National Laboratory, Lemont, Illinois 60439, United States.
ACS Nano
|September 1, 2020
Summary
Intersubband relaxation in colloidal quantum wells is rapid (<1 ps), driven by phonon and surface scattering. This fast process may limit mid-infrared detectors but benefit optical switching applications.
Area of Science:
- Materials Science
- Quantum Optics
- Nanotechnology
Background:
- Intersubband relaxation dynamics are crucial for quantum well devices like lasers and photodetectors.
- Colloidal quantum wells (CQWs), or nanoplatelets, offer tunable optoelectronic properties.
Purpose of the Study:
- To investigate intersubband relaxation in CdSe colloidal quantum wells.
- To understand the influence of size, ligand chemistry, temperature, and excitation intensity on relaxation dynamics.
Main Methods:
- Utilized pump-push-probe transient spectroscopy to study electron dynamics.
- Excited electrons between conduction bands and monitored cooling to the band edge.
Main Results:
- Intersubband relaxation in CQWs is rapid (<1 ps), significantly faster than intraband relaxation in quantum dots.
- Larger CQW size, thiolate ligands, low temperatures, and high excitation fluences slow relaxation.
- LO phonon and surface scattering are identified as primary drivers of rapid relaxation.
Conclusions:
- The rapid intersubband relaxation in CQWs may impede applications in mid-infrared detection.
- The fast relaxation dynamics could be advantageous for optical switching technologies.
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