Thermal annealing induced structural and optical properties of Ca doped ZnO nanoparticles
In this letter, the effects of annealing on structural and optical properties of Ca doped ZnO nanoparticles have been investigated. X-ray diffraction analysis reveals that the prepared particles are in hexagonal wurtzite structure and formation of secondary phase related to the Calcite was found after thermal annealing. UV–Vis measurements show free exciton absorption band appeared at 372 nm and increase of band gap with annealing of samples. Room temperature photoluminescence (PL) spectrum of the prepared Ca doped ZnO nanoparticles shows bands which belong to the near band edge emission at 377 nm and green emission at 556 nm. Annealed samples exhibit enhancement in the blue emission band. Raman spectra show the increment in the electron–phonon coupling value with annealing.