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Strong Absorption Enhancement in Si Nanorods
Ilya Sychugov1, Fatemeh Sangghaleh1, Benjamin Bruhn1
1Materials and Nano Physics Department, KTH - Royal Institute of Technology , Kista, Stockholm, 16440, Sweden.
Nano Letters
|December 15, 2016
Summary
Silicon nanorods show significantly enhanced light absorption compared to bulk silicon. This improvement stems from local field effects and transition matrix elements, paving the way for better optoelectronics.
Area of Science:
- Nanotechnology
- Materials Science
- Optoelectronics
Background:
- Silicon is an indirect band gap material, limiting its efficiency in optoelectronic devices.
- Understanding light-matter interactions in nanostructured silicon is crucial for enhancing its optical properties.
Purpose of the Study:
- To investigate the enhanced light absorption in silicon nanorods compared to bulk silicon.
- To experimentally and computationally disentangle the contributions of local field enhancement and dipole matrix elements to absorption.
- To explore the potential of nanostructure shape engineering for optoelectronic applications.
Main Methods:
- Single-dot absorption measurements on silicon nanorods of varying shapes.
- Varying excitation polarization and photon energy during measurements.
- Simulations of light-matter interactions.
- Atomistic calculations of transition matrix elements.
Main Results:
- Observed two orders of magnitude stronger absorption in silicon nanorods versus bulk silicon.
- Demonstrated substantial contributions from both local field enhancement and dipole matrix elements.
- Identified a strong dependence of quasidirect transitions on nanocrystal shape.
Conclusions:
- Silicon nanostructure shape engineering is a viable strategy to enhance light absorption.
- This approach can help overcome the limitations of indirect band gap materials in silicon-based optoelectronics.
- Optimized nanorod shapes can significantly improve the performance of devices like solar cells.
