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Light‐Emission Performance of Silicon Nanocrystals Deduced from Single Quantum Dot Spectroscopy
Author(s) -
Valenta Jan,
Fucikova Anna,
Vácha František,
Adamec František,
Humpolíčková Jana,
Hof Martin,
Pelant Ivan,
Kůsová Kateřina,
Dohnalová Kateřina,
Linnros Jan
Publication year - 2008
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.200800397
Subject(s) - nanocrystal , materials science , photoluminescence , quantum dot , auger effect , exciton , quantum yield , spectroscopy , excitation , optoelectronics , silicon , molecular physics , auger , nanotechnology , atomic physics , optics , fluorescence , physics , condensed matter physics , quantum mechanics
Spectra of individual silicon nanocrystals within porous Si grains are studied by the wide‐field imaging microspectroscopy and their ON – OFF blinking is detected by the confocal single‐photon‐counting microscopy. Observed spectral and blinking properties comprise all features reported before in differently prepared single Si nanocrystals (SiNCs). Former apparently contradictory results are shown to be due to different experimental conditions. When the effect of dark periods ( OFF switching) is removed the common ultimate photoluminescence properties of SiO 2 passivated SiNCs are found, namely the quantum efficiency (QE) of about 10–20% up to the pumping rate corresponding to one exciton average excitation per quantum dot. At higher pump rates the QE is slowly decreasing as the 0.7th power of excitation. This is most likely due to Auger recombination which, however, seems to be weakened compared with measurements of nanocrystal assemblies. We conclude that SiNCs may be pumped above one exciton occupancy to yield a higher light emission, being advantageous for applications.