Synthesis and characterization of germanium/Si-alkyl and germanium/silica core-shell quantum dots
Ge/Si-R and Ge/SiO{sub 2} core-shell nanoparticles have been synthesized by a solution route from the stepwise reactions of the Zintl salt, Mg{sub 2}Ge, with SiCl{sub 4} and subsequently either RLi (R = butyl) or H{sub 2}O{sub 2}. High-resolution transmission electron microscopy (HRTEM) images show that the core part of these Ge/Si-R and Ge/SiO{sub 2} nanoparticles is crystalline and the d spacing of lattice fringes agrees with the {l{underscore}brace}111{r{underscore}brace} crystal plane (3.27 {angstrom}) of Ge. The average sizes (diameter) are 5.8(2.3) and 6.8(2.8) nm for Ge/Si-R and Ge/SiO{sub 2}, respectively. Fourier transform-infrared (FTIR) spectra are consistent with alkyl groups bonded to the silicon surface in Ge/Si-R nanoclusters. Off-axis holography was performed for several Ge/SiO{sub 2} nanoparticles. The characterization of the ratio of radii and geometry between the core part and the outer sphere of Ge/SiO{sub 2} is presented. The reconstructed phase image from the hologram offers detailed information concerning the ratio of the shell thickness (R - r) to the radius of the core (r), Rr - (R - r)/r, by measuring the phase shift and the resultant phase contrast. The Rr value from the deconvoluted phase image of a 16 nm sphere-like Ge/SiO{sub 2} is 0.264 (0.065). Photoluminescence (PL) spectra of both Ge/Si-R and Ge/SiO{sub 2} nanoclusters show a strong UV-blue PL with a peak centered between 400 and 410 nm. These results suggest that the UV-blue PL may be attributed to the core part of these nanoparticles.
- Research Organization:
- Univ. of California, Davis, CA (US)
- Sponsoring Organization:
- National Science Foundation (NSF); USDOE
- DOE Contract Number:
- W-7405-ENG-48; AC03-76SF00098
- OSTI ID:
- 20014841
- Journal Information:
- Chemistry of Materials, Vol. 11, Issue 12; Other Information: PBD: Dec 1999; ISSN 0897-4756
- Country of Publication:
- United States
- Language:
- English
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