Synthesis and photoluminescence enhancement of pure CdO: Annealing effect study

The effect of post-preparation annealing on the structure and photoluminescence of CdO samples prepared by precipitation method are described. The particle size was shifted towards higher values in nanometer range as examined by particle size analyzer upon annealing at higher temperatures. While X-ray diffraction pattern revealed phase pure CdO with cubic crystal structure for the annealed sample. The scanning electron microscopy with energy dispersive X-ray analysis confirmed the origin of defects due to the presence of chlorine (CdCl). Furthermore, the Raman bands obtained at 400 and 450 cm⁻¹ confirmed the isolation of pure CdO, which correspond to two-phonon combinations such as longitudinal optical (LO) mode and transverse optical (TO) + transverse acoustic (TA) combination at the CdO Brillouin zone. Both the as-prepared and annealed CdO samples exhibited blue emission at about 430 nm upon excitation at 320 nm. Decay-associated spectra (DAS) were extracted from global analysis of time-resolved emission spectra of CdO powders. It reveals switching of emission decays from bi-exponential to mono-exponential (0.9 ns) in the annealed CdO powder at 600 °C. The enhancement in photoluminescence with the concomitant mono-exponential emission decay as induced by annealing should have potential implication for advancing the technology of optoelectronic micro/nano devices.