Synthesis and characterization of CdS nanocrystals embedded in germanate glasses

Cadmium sulfide nanoparticles were grown in Na2O–GeO2 glass matrix by a diffusion-controlled phase decomposition of over-saturated solid solution. The structural properties of CdS nanocrystals have been studied by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), optical absorption and electrical conductivity. The existence of CdS nanocrystals was confirmed by XRD and TEM, also its crystallite sizes are obtained. The average CdS crystallite sizes calculated from XRD analysis for the different heat-treatment conditions are found in the range between 23.7 and 48.8 nm; however, the average CdS crystallite sizes obtained from TEM micrographs are found in the range between 17 and 63 nm. The band gap energy E opt and the activation energy E g for the electrical conductivity have been increased with decrease in the particle size; however, the Urbach energy ΔE decreases with decreasing the nanocrystal size.