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Transfer mechanisms in semiconductor hybrids with colloidal core/shell quantum dots on ZnSe substrates
M Wilhelm1, S C Kommadath1, W Heimbrodt1
1Department of Physics, Philipps-University of Marburg, Renthof 5, D-35032 Marburg, Germany.
Nanotechnology
|September 14, 2020
Summary
Quantum dot hybrid systems show size-dependent energy transfer mechanisms. Electron and hole tunneling dynamics vary with CdS core size, impacting charge transport in CdS/ZnS on ZnSe substrates.
Area of Science:
- Materials Science
- Semiconductor Physics
- Nanotechnology
Background:
- Colloidal quantum dots (QDs) offer tunable optoelectronic properties.
- Hybrid systems integrate QDs with semiconductor substrates for advanced functionalities.
- Understanding charge transfer dynamics is crucial for device optimization.
Purpose of the Study:
- Investigate energy and charge transfer mechanisms in CdS/ZnS core/shell quantum dots on ZnSe substrates.
- Determine the influence of CdS core size on dominant transfer processes.
- Quantify the conduction band offset between CdS and ZnSe.
Main Methods:
- Continuous-wave and nanosecond time-resolved photoluminescence spectroscopy.
- Kinetic calculations to model transfer processes.
- Analysis of carrier tunneling, resonance energy transfer, and photon reabsorption.
Main Results:
- Dominant transfer mechanisms vary with CdS core size.
- Carrier tunneling observed for QDs in direct contact with the ZnSe substrate.
- Hole tunneling significant for large QDs; fast electron tunneling decisive for small QDs.
- Conduction band offset between CdS and ZnSe determined to be 0.56 eV at 10 K.
Conclusions:
- Size-dependent charge transfer governs hybrid QD system behavior.
- Electron and hole tunneling are key mechanisms, influenced by QD size and substrate contact.
- The determined band offset provides critical data for designing heterojunction devices.
