Structural, optical, photoluminescence and magnetic investigation of doped and Co-doped ZnO nanoparticles

We report here the structural, optical, photoluminescence (PL), and magnetic investigation of Zn1-x-yFexMyO nanoparticles. The lattice constants and crystallite size are decreased by Fe, followed by a further decrease up to (Fe + M) = 0.30. A compressive stress is approved and the size of particle is between 180 and 277 nm and follows the sample order of ZnO, (Fe + Cu), (Fe + Ni), and Fe. Although a single value of energy gap (E-g) is found for pure and Fe-doped ZnO, two values of E-g (E-gh and E-gl) are found for the co-doped samples. The E-g is generally increased by Fe, followed by a further increase for the Cu-series, whereas it is decreased for the Ni-series. The refractive indices n(K) and n(T) proposed by different methods are generally decreased by Fe, followed by a further decrease for both series. Although Fe doped ZnO depressed the density of carriers (N/m*), it increased again for the co-doped samples. The residual dielectric constant epsilon(L) is decreased by Fe, followed by an increase for the Cu-series, but it is decreased for the Ni-series. The loss factor tan delta increases slightly with Fe, followed by an increase for the Ni-series, but it decreases in the Cu-series. A significant depression of optical conductivity sigma(opt) by Fe was obtained, followed by a further decrease which is higher for the Cu-series. The PL shows four visible emissions. Interestingly, an IR emission at about 825 nm is only obtained for the co-doped samples. Furthermore, the blue emission (I-blue) was higher than UV (I-UV), [(I-blue/I-UV) > 1], but it is greater for the Ni series than the Cu. Although ZnO exhibits diamagnetic behavior, the Fe and co-doped samples exhibit ferromagnetic with higher magnetization for the Ni-series than the Cu. The current results recommend the co-doped samples in nanoscale for some of advanced devices.

Automated summary

We investigated the structural, optical, photoluminescence (PL), and magnetic properties of Zn1-x-yFexMyO nanoparticles. The lattice constants and crystallite size decreased with increasing Fe content, and further decreased up to (Fe + M) = 0.30. Fe doping led to a compressive stress and the particle size ranged from 180 to 277 nm in the order of ZnO, (Fe + Cu), (Fe + Ni), and Fe samples. While pure and Fe-doped ZnO had a single energy gap (E-g), co-doped samples exhibited two energy gaps (E-gh and E-gl). Fe generally increased E-g, followed by a further increase in the Cu-series and a decrease in the Ni-series. Refractive indices n(K) and n(T) decreased with Fe, with a further decrease in both series. Although Fe doping reduced the carrier density (N/m*), it increased again in the co-doped samples. Fe decreased the residual dielectric constant epsilon(L), followed by an increase in the Cu-series but a decrease in the Ni-series. The loss factor tan delta slightly increased with Fe, followed by an increase in the Ni-series and a decrease in the Cu-series. Fe significantly depressed the optical conductivity sigma(opt), followed by a further decrease, particularly in the Cu-series. PL measurements showed four visible emissions, and an infrared emission at around 825 nm was only observed in the co-doped samples. The blue emission (I-blue) was higher than the ultraviolet emission (I-UV), [(I-blue/I-UV) > 1], and the Ni series had a greater blue emission than the Cu series. ZnO exhibited diamagnetic behavior, while Fe and co-doped samples exhibited ferromagnetic behavior, with higher magnetization in the Ni-series than the Cu. Overall, the results suggest that co-doped samples at the nanoscale have potential applications in advanced devices.