J. Allegre et al., ABSORPTION PROPERTIES OF CDS NANOCRYSTALS IN GLASSES - EVIDENCE OF BOTH WEAK AND STRONG CONFINEMENT REGIMES, Journal of crystal growth, 138(1-4), 1994, pp. 998-1003
Experimental evidence of both weak and strong confinement regimes is r
eported on CdS nanocrystals embedded in glass matrix. Classic methods
for nanocrystallite preparation meet a principal difficulty, the polyd
ispersion in size of crystallites due to several difficulties such as
coalescence and decomposition of particles with time and high temperat
ures. In this work, we used a new route to elaborate CdS-doped sodium
borosilicate glass from gel formed in an aqueous medium. Our vitreous
matrix is fully and swiftly densified at relatively low temperature, p
roviding us with CdS nanocrystallites yielding fine band-edge structur
e and small size dispersion. Low temperature absorption spectra have b
een interpreted in terms of excitons and electron-hole confinements, t
aking account of both a Lorentzian broadening of the energy states ins
ide each nanocrystal and a Gaussian size-distribution. It has been sho
wn that, for very small crystallites, the strong blue-shift of the abs
orption edge due to the quantum size effects, is partially compensated
by a red-shift associated to the size distribution.