Role of defects and oxygen vacancy on structural, optical and electronic structure properties in Sm-substituted ZnO nanomaterials

Co-precipitation route synthesized undoped ZnO and Sm-substituted ZnO nanomaterials are characterized using XRD, UV-Vis-NIR spectroscopy, Raman Spectroscopy, HRTEM and XAS techniques. Rietveld-refined XRD patterns and Raman spectra correspond to wurtzite structure similar to ZnO for all samples. For Sm-substituted ZnO samples, observed fluctuating lattice parameters suggest dopant-induced agitation in host lattice. Full incorporation of Sm cation can be seen by wurtzite ZnO nanolattice but for higher doping ,Sm cation is not fully incorporated and a new cubic phase of Sm2O3 is observed with our XRD and Raman analyses. From our TEM micrographs, particle sizes of undoped ZnO and Sm-substituted ZnO samples are found between 21 and 24 nm in spherical shape for undoped ZnO and nanorods for Sm-substituted ZnO samples. Absorption spectra analyses report a decrease in bandgap energy for Sm-substituted ZnO samples from 3.20 to 3.16 eV. X-ray absorption edges of Zn L-2,L-3 edge, O K edge and Sm M-4,M-5 edge measurements confirm the valence state of Sm cations is + 3 and the valence state of Zn ions is + 2 along with an increase in introduction of oxygen vacancies with Sm substitution in nanolattice. These nanoparticles can be suitable alternatives for various applications like oxygen transportation, UV blockers, photocatalyst and optoelectronics.

Automated summary

The undoped ZnO and Sm-substituted ZnO nanomaterials synthesized by co-precipitation route were characterized using various techniques. The results show that the samples have a wurtzite structure similar to ZnO, with observed fluctuating lattice parameters and a new cubic phase of Sm2O3 for higher dopant levels. TEM images reveal different shapes of nanoparticles. Absorption spectra analysis indicates a decrease in bandgap energy for Sm-substituted ZnO samples. X-ray absorption edge measurements confirm the introduction of oxygen vacancies with Sm substitution and verify the valence states of Sm cations and Zn ions.