Annealing effects on photoluminescence of ZnO nanoparticles

• Published in: Materials letters 2013-11, Vol.110, p.10-12
• Main Authors: Sowri Babu, K., Ramachandra Reddy, A., Sujatha, Ch, Reddy, K.V.G., Mallika, A.N.
• Format: Article
• Language: English
• Subjects: Annealing; evaporation; ionization; Luminescence; nanoparticles; oxygen; Semiconductors; temperature; X-ray diffraction; zinc; zinc oxide; ZnO
• ISSN: 0167-577X; 1873-4979
• DOI: 10.1016/j.matlet.2013.07.114

In this study, the effects of annealing temperature on photoluminescence (PL) of ZnO nanoparticles were studied. ZnO was annealed at various temperatures between 600 and 900°C. The X-ray diffraction (XRD) results demonstrated that grain size increased with increase of annealing temperature. As the annealing temperature increased from 600 to 800°C, the intensities of both UV peak and that of green luminescence (GL) enhanced monotonously but reduced at 900°C. The enhancement in the UV peak intensity is attributed to the decrease of grain boundaries and surface states; whereas, the remarkable improvement in the GL is assigned to the out-diffusion of oxygen from the sample up to 800°C. It supports that GL is induced by the singly ionized oxygen vacancies. These oxygen vacancies are saturated due to the finiteness of the defects at 800°C. So, it is speculated that the deterioration of GL intensity at 900°C is due to the evaporation of Zn which is predominant at temperatures higher than 850°C. •The intensities of the UV and GL increased up to 800°C and decreased at 900°C.•Intensity variations were explained by taking the out diffusion of oxygen and zinc.•These results confirmed that GL is caused by the singly ionized oxygen vacancies.