Optical properties of passivated Si nanocrystals and SiO{sub {ital x}} nanostructures
- Department of Applied Science, University of California, Davis/Livermore, California (United States)
- Chemistry and Materials Science Department, University of California, Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)
- Department of Applied Science, University of California, Davis/Livermore, California 94550 (United States)
Thin films of Si nanoclusters passivated with oxygen or hydrogen, with an average size of a few nanometers, have been synthesized by thermal vaporization of Si in an Ar buffer gas, followed by subsequent exposure to oxygen or atomic hydrogen. High-resolution transmission electron microscopy and x-ray diffraction revealed that these nanoclusters were crystalline. However, during synthesis, if oxygen was the buffer gas, a network of amorphous Si oxide nanostructures (an-SiO{sub {ital x}}) with occasional embedded Si dots was formed. All samples showed strong infrared and/or visible photoluminescence (PL) with varying decay times from nanoseconds to microseconds depending on synthesis conditions. Absorption in the Si cores for surface passivated Si nano- crystals (nc-Si), but mainly in oxygen related defect centers for an-SiO{sub {ital x}}, was observed by photoluminescence excitation spectroscopy. The visible components of PL spectra were noted to blueshift and broaden as the size of the nc-Si was reduced. There were differences in PL spectra for hydrogen and oxygen passivated nc-Si. Many common PL properties between oxygen passivated nc-Si and an-SiO{sub {ital x}} were observed. Our data can be explained by a model involving absorption between quantum confined states in the Si cores and emission for which the decay times are very sensitive to surface and/or interface states. The emission could involve a simple band-to-band recombination mechanism within the Si cores. The combined evidence of all of our experimental results suggests, however, that emission between surface or interface states is a more likely mechanism. {copyright} {ital 1996 The American Physical Society.}
- Research Organization:
- Lawrence Livermore National Laboratory
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 286725
- Journal Information:
- Physical Review, B: Condensed Matter, Journal Name: Physical Review, B: Condensed Matter Journal Issue: 7 Vol. 54; ISSN 0163-1829; ISSN PRBMDO
- Country of Publication:
- United States
- Language:
- English
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