Raman spectroscopy study of structural disorder degree of ZnO ceramics

A detailed study of Raman line-shape of low and high dense ZnO ceramics was carried out using a Raman microprobe system with a solid-state laser source of 532 nm wavelength and 100 mW power at room temperature. The Raman activated bands for the ZnO wurtzite structure were observed in both samples. The line-width, asymmetry parameter, and Raman shift were determined by fitting the Raman spectra to Breit-Wagner-Fano (BWF) function and the degree of lattice disorder in the wurtzite structure were investigated by phonon confinement physical models (PCM). The correlation length (L) and defect concentration (N) could be estimated based on the spatial correlation model, being 3.01 nm and 3.15 nm (E2low mode) and 2.70 nm and 2.83 nm (E2high mode) and 8.84×1018cm−3 and 7.64×1018cm−3 (E2low mode) and 1.21×1019cm−3 1.05×1019cm−3 (E2high mode) for ZnO-LD and ZnO-HD samples, respectively. Since the E2low and E2high Raman phonon modes are sensitive to vibration in Zn sub-lattice and oxygen vacancy, respectively, the results indicated that low dense samples have a higher level of both defects.