ZnS nanocrystals embedded in SiO2 matrix

Growing nanocrystals in a matrix is a way to have separate, non-agglomerated nanoparticles, which are surface passivated and stabilized against environmental attacks. To create nanocrystals of the desired size and properties in a matrix, it is required that the growth parameters are properly tuned. In this work, we study the growth parameters for ZnS nanocrystals in an SiO2 matrix. Samples were prepared by cosputtering of SiO2 and ZnS on a silica substrate, followed by annealing at different temperatures. Two categories of samples with low-content ZnS (View the MathML source) and high-content ZnS (View the MathML source) were examined. In the low-content samples, ZnS nanocrystals are not formed below 900°C annealing temperature. However in high-content samples, ZnS nanocrystals can be observed even in unannealed samples. Upon annealing to higher temperatures, nanocrystals grow in size and undergo phase change from cubic to hexagonal at temperatures between 700–800°C. There are side reactions, in particular the formation of zinc silicate, that occur as a result of annealing in both low- and high-content samples.