Influence of high temperature annealing on the magnetic and the structural properties of co ion-implanted-ZnO single crystals

Abstract

Co- ions of 80 keV at a dose of 3 x 10(16) cm(-2) were implanted in single-crystal ZnO (0001) substrates at 350 degrees C and subsequently annealed at 700 - 900 degrees C. The properties of Co-ion-implanted ZnO were investigated by using various measurements. X-ray diffraction results showed the presence of Co impurities in the samples annealed at 700 - 900 degrees C. The Co K-edge X-ray absorption near-edge structure and extended X-ray absorption fine structure revealed the coexistence of Co-O and Co-Co bonds in the films. The magnetization curves and the temperature dependence of magnetization taken in zero-field-cooling (ZFC) and field-cooling (FC) conditions showed the features of a superparamagnetic system due to the presence of magnetic clusters. The blocking temperature (T-B) increased with increasing annealing temperature. In the PL spectra obtained at 10 K, noticeable difference in the near-band-edge and the green-band photoluminescences between unimplanted and implanted ZnO films with post-annealing were observed.