Zinc incorporation into CdTe quantum dots in glass

Abstract

We report zinc incorporation into CdTe nanoparticles grown by two-step solid phase precipitation in commercial borosilicate glass quenched from the melt, based on a co-evaluation of the results of resonant Raman and optical absorption measurements. Resonant Raman spectra display a two-peak structure at wave-number positions corresponding to ternary compound Zn(x)Cd(1-x)Te. We attribute the higher intensity peak between 190 and 195 cm(-1) to the first harmonic of the zone-center longitudinal optical mode (LO(1)) and, the lower intensity peak between 157 and 160 cm(-1) to the second harmonic (LO(2)) of Zn(x)Cd(1-x)Te crystal. The wave-number of vibrational Raman modes indicates that zinc content varies between 39 and 50% during the growth of quantum dots. The asymptotic absorption edge against heat-treatment time plot extrapolates to a bulk band gap of 1.714 eV which sets a lower limit of 31% for zinc incorporated into quantum dots which is consistent with the results of resonant Raman measurements. The energetic position of asymptotic absorption edge of 1.592 eV and an additional unresolved weak structure in Raman spectrum between 166 and 182 cm-1 observed for as-received glass might serve as a evidence for the occurrence of a different nanocrystalline phase with 13% zinc content. (C) 2009 Elsevier B.V. All rights reserved.