Influence of Cd on optical and photoluminescence behavior of Zn0.98-xCdxMn0.02S quantum dots under Ar atmosphere

In the present study, Zn0.98-xMn0.02CdxS (x = 0, 0.02 and 0.04) quantum dots have been successfully synthesized using co-precipitation method. X-ray diffraction (XRD) study confirmed substitution of Cd, Mn well in ZnS host with existing cubic structure. The average size of the particles was measured from XRD pattern and it was ∼2 nm. The SEM study was taken to reveal the surface morphology of the samples. EDX spectra evidenced the existence of Cd, Mn, Zn and S in the samples as per the targeted stoichiometry. FTIR spectra confirmed the presence of peaks which corresponding to molecules present in the samples. UV-visible absorption and transmission spectra were studied and high intensity of absorption was received for the higher composition of Cd. A huge suppression was noticed in transmission peaks during Cd addition. When 2% of Cd added with Mn: ZnS, A small blue shift was identified and got redshift for higher concentration of Cd. Band gap values were tuned from 3.79 eV to 3.98 eV and discussed based on the quantum confinement effect. From this tailoring of band gap and optical property, these materials shall be selected for optoelectronic device applications. A room temperature photoluminescence study was carried out and sharp as well as strong UV band emissions were observed. Blue and green emission bands were also exhibited by Cd doping. The variations in luminescence intensities were discussed in terms of the crystallite size and defect state formation.