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Enhanced surface-excitonic emission in ZnO/Al(2)O(3) core-shell nanowires
J-P Richters1, T Voss, D S Kim
1Institute of Semiconductor Optics, University of Bremen, Otto-Hahn-Allee 1, D-28359 Bremen, Germany.
Nanotechnology
|August 11, 2011
Summary
Adding an aluminum oxide shell to zinc oxide nanowires significantly reduces green defect emission. This shell also enhances surface exciton bands at low temperatures, offering new insights into nanowire photoluminescence.
Area of Science:
- Materials Science
- Nanotechnology
- Solid State Physics
Background:
- Zinc oxide (ZnO) nanowires are crucial for optoelectronic applications.
- Understanding photoluminescence (PL) is key to optimizing ZnO nanodevices.
- Defect emission in ZnO can hinder performance.
Purpose of the Study:
- To investigate the effect of an aluminum oxide (Al2O3) shell on ZnO nanowire photoluminescence.
- To analyze changes in near-band-edge (NBE) and defect emission.
- To study the influence of temperature and annealing on PL spectra.
Main Methods:
- Fabrication of ZnO/Al2O3 core-shell nanowires.
- Photoluminescence spectroscopy at room temperature and 5 K.
- Annealing experiments at 500 °C.
Main Results:
- The Al2O3 shell significantly reduced the relative intensity of green defect emission compared to NBE emission at room temperature.
- At 5 K, the surface exciton band intensity increased relative to the donor-bound exciton emission.
- Annealing at 500 °C did not enhance green defect luminescence at 5 K.
Conclusions:
- The Al2O3 shell effectively passivates surface defects in ZnO nanowires, suppressing green emission.
- Surface passivation by the Al2O3 shell influences exciton dynamics at low temperatures.
- A model is proposed to explain the observed spectral modifications due to the Al2O3 shell.
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