Viscosity dependant CdS nanocrystals embedded in silicate glass

Abstract

An explicit role of viscosity on the growth of semiconductor nanocrystals dispersed in silicate glass matrix is investigated. Theoretically, a simplified Arrhenius equation, lnh = A + B/T (where h 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 bang gap of CdS quantum dots ranges from bulk band gap 2.4eV to 3.2eV which confirms the strong confinement of quantum dots. Photoluminescence measurements explain the observed absorption results qualitatively. CdS doped glass samples showed the red shift of emission wavelength as the thermal treatment time and temperature increased which justifies the viscosity dependence on cluster size.