The role of glass-viscosity on the growth of semiconductor quantum dots in glass matrices

Abstract

The dependence of glass viscosity on the growth of semiconductor (CdS) quantum dots in borosilicate glass matrices is studied systematically. The glass viscosity was varied (3000–260 000 Pa s) by varying the glass compositions of constituent oxides and growth temperatures. Thus, grown dot sizes at various growth times (2–48 h) were in the range 2–30 nm. The linear variation of dot size with cube root of growth time confirms the diffusion controlled growth. The growth of dot size was found to vary linearly with the inverse cube root of glass viscosity. The excitonic peak energy of the dots was found to vary linearly with inverse square of the dot size consistent with the quantum confinement effect. This analysis yields the bulk value of energy gap Eg (bulk) = 2.47 eV and the reduced effective masses as μ = 0.138 for CdS consistent with the values available in the literature. The emission (photoluminescence) spectra further support the absorption results.