Influence of Cu doping on the microstructure, optical properties and photoluminescence features of Cd0.9Zn0.1S nanoparticles

Abstract

Cd0.9−xZn0.1CuxS (0≤x≤0.06) nanoparticles were successfully synthesized by a conventional chemical co-precipitation method at room temperature. Crystalline phases and optical absorption of the nanoparticles have been studied by X-ray diffraction (XRD) and UV–visible spectrophotometer. XRD confirms the phase singularity of the synthesized material, which also confirmed the formation of Cd–Zn–Cu–S alloy nanocrystals rather than separate nucleation or phase formation. Elemental composition was examined by the energy dispersive X-ray analysis and the microstructure was examined by scanning electron microscope. The blue shift of absorption edge below Cu=2% is responsible for dominance of Cu+ while at higher Cu concentration dominated Cu2+, d–d transition may exist. It is suggested that the addition of third metal ion (Cu2+/Cu+) is an effective way to improve the optical property and stability of the Cd0.9Zn0.1S solid solutions. When Cu is introduced, stretching of Cd–Zn–Cu–S bond is shifted lower wave number side from 678cm−1 (Cu=0%) to 671cm−1 (Cu=6%) due to the presence of Cu in Cd–Zn–S lattice and also the size effect. The variation in blue band emission peak from 456nm (∼2.72eV) to 482nm (∼2.58eV) by Cu-doping is corresponding to the inter-band radiation combination of photo-generated electrons and holes. Intensity of red band emission centered at 656nm significantly increased up to Cu=4%; beyond 4% it is decreased due to the quenching of Cu concentration.