Glass viscosity dependant growth of CdS nanocrystals in silicate glass matrix

Abstract

An explicit role of glass viscosity on the growth of semiconductor nanocrystals dispersed in silicate glass matrix is investigated. A simplified Arrhenius type equation, lnη = A + B/T (where η is viscosity) is used to calculate the viscosities of various glass compositions. Using Diffusion - Controlled Growth model it is established that average radius of grain (QD) is inversely proportional to the cube root of the viscosity of supersaturated solid solution. Experimental evidences show that grown dot size is ranging from 2nm to 20 nm for various growth times (2-50 hr). A blue shift was observed in optical absorption edge. The optical absorption spectra depict that the bang gap of CdS quantum dots blue shifts (from bulk value of 2.4eV to 3.2eV) with decreasing dot size confirming the strong confinement of quantum dots. Photoluminescence measurements also support and explain the observed absorption results. CdS doped glass samples showed the red shift of emission wavelength with the thermal treatment time and temperature which justifies the viscosity dependant growth of dot size.