The effect of annealing on the properties of nanoparticles dispersed in oxide glass containing Zn

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Abstract
The optical and vibrational properties of nanoparticles dispersed in oxide glass containing Zn are investigated as functions of the annealing temperature using photoluminescence, optical absorption and Raman spectroscopy. Upon annealing the samples, a blue-shift of the optical absorption and photoluminescence is observed, in contrast to the expected red-shift due to particle growth. This can be understood if one invokes the inclusion of Zn into the particle which more than compensates the red-shift due to particle growth. The observed increase in the LO phonon frequency upon annealing also confirms this. The particle size, obtained from the analysis of low-frequency Raman spectra in terms of confined acoustic phonons, shows considerable growth upon annealing above . Overtones up to 3-LO are identified. Furthermore, the LO phonon and its overtones are found to exhibit strong resonance enhancement as a function of exciting wavelength. However, upon annealing, the Raman intensities reduce dramatically due to the shift of the electronic transition energy away from that of the incident photon.