Phonon confinement and substitutional disorder in Cd1-xZnxS nanocrystals

1-longitudinal optical (LO) phonons in free-standing mixed Cd1-xZnxS nanocrystals, synthesized using chemical precipitation, are investigated using Raman spectroscopy. As expected for the nanocrystals, the 1-LO modes are found to appear at slightly lower wavenumbers than those in the bulk mixed crystals and exhibit one-mode behavior. On the other hand, the line broadening is found to be much more than that can be accounted on the basis of phonon confinement. From the detailed line-shape analysis it turns out that the substitutional disorder in the mixed crystals contributes much more to the line broadening than the phonon confinement. The linewidth arising from these mechanisms are also extracted from the analysis. Copyright (C) 2009 John Wiley & Sons, Ltd.