Erbium- and Yttrium-Doped Zinc Sulphide Quantum Dots with Tuneable Optical Properties Required for Optoelectronic Devices

In the present paper crystalline single-phase zinc sulphide, undoped as well as doped with Yb+3, Er+3/Yb+3 (Co-doped) in molar concentration of 1%, 2% and 3% is prepared using simple and cost-effective co-precipitation method. The structural morphology such as shape, size and surface states is characterized using high resolution transmission electron microscope, energy-dispersive X-ray spectroscopy (EDAX), UV-Visible, photoluminescence (PL) and X-ray diffraction. The spherical nanomaterial is prepared with cubic blende structure, and they are uniformly distributed. The crystallite size of the QDs is approximately 3.6 nm, i.e. in quantum confinement region. The particle size decreased for Yb+3 as compared to Er+3 with the increase in molar concentration. EDAX report confirmed the presence of Zn, S, Er and Yb elements. UV-Vis analysis showed that the blue shift is more pronounced for Er+3 as compared to Yb+3 with a band gap of 3.7 eV for Er+3 and 3.6 eV for Yb+3. PL spectra showed the presence of three bands at 398 nm, 466 nm and 526 nm. It is observed that on doping the peak position did not change but the intensity varied.