In this experiment, pure, Y 3+ doped ZnO and Cu 2+ + Y 3+ co-doped ZnO were synthesized by a solution combustion method. The Y 3+ dopant concentration was fixed in 3%wt. and the Cu 2+ dopant concentrations were 0, 1, 2, 3, 10, and 20%wt. The XRD spectra showed that the original hexagonal wurtzite structure of ZnO is conserved after doping process, an increasing red shift until 10%wt. Cu 2+ doping and decrease at higher Cu 2+ doping and also, the chemical creation of the news Y 2O 3 and Y 2Cu 2O 5 phases. The behavior of the photoluminescence of the samples as a function of Cu 2+ doping reveal that the green emission band of the ZnO is quenching and the ZnO UV emission intensity decrease notably for all Cu 2+ doping. The scanning electron microscope analysis of the Cu 2+ + Y 3+ co-doped ZnO samples reveal the existence of grains agglutinated forming like-spheres particles. However, the nano-sized characteristic of the crystals is confirmed.
The zinc oxide (ZnO) is one of the oldest n-type semiconductor material studied, and is actually a promising material in fundamental studies and technological applications due to its varied and outstanding properties such as: high conductance and transparence in thin films, chemical and thermal stability, wide band gap (3.37 eV) and a large exciton binding energy (60 meV) [
The experimental method of chemical synthesis solution combustion [
Pure and Cu2+ + Y3+ doped ZnO samples were obtained by a solution combustion technique by means of the following redox chemical reaction stoichiometric:
3Zn ( NO 3 ) 2 × 6H 2 O + 5H 2 NCONH 2 + 2 ( YCl 3 + CuCl 3 ) → 3ZnO + 10H 2 O + 5CO 2 + 8N 2 + 2 ( Cu 2+ + Y 3+ ) + 5Cl 2 (1)
The Equation (1) was obtained by taken into account the oxidizer/fuel molar radio (O/F = 1) required for a stoichiometric mixture which is determined by summing the total oxidizing and reducing valences in the oxidizer compound and dividing it by the sum of the total oxidizing and reducing valences in the fuel compound [
The XRD patterns of Y3+ doped ZnO with 3%wt. and Cu2+ + Y3+ co-doped ZnO with 3%wt. of Y3+ ion and 1, 3, 5, 10, and 20%wt. of Cu2+ ion concentrations and after annealed at 835˚C by 2 h are showed in
oxygen with the Zn2+ atoms increasing the peak intensity. After 10%wt. the peak intensity decrease, due to excess of Cu2+ atoms that are energetically efficient to coalesce into metallic copper cluster decreasing the peak intensity [
D = 0.9 λ β cos θ (2)
where λ is the X-ray wavelength used (1.5406Å), β is the full width at half maximum (FWHM) along (101) plane and theta is the Bragg diffraction angle. The
size as a function of Cu2+ ion concentration respectively, it is observed from
The
ious Cu2+ ion concentrations values of 2, 3, 5, 10 and 20%wt., it is clearly observed that for all Cu2+ concentration the green PL emission due to free exciton recombination has been quenched by the intercalation of Cu2+ ions into Y3+ + ZnO host lattice; this quenching effect is attributed to a non-radiative recombination process known as non-radiative recombination Auger phenomena which is associated to degenerate electrons, in which the energy released by an electron is immediately recombined and absorbed by another electron and the energy involved is dissipated by phonons. Auger process is considered as the cause major of non-radiative recombination in semiconductor materials. Auger process depends on the doping atoms concentration and defects in the lattice. [
The scanning electron microscope (SEM) technique has been used to observe the surface morphology (SM) of the particles. The Figures 6(a)-(d) exhibits the SEM images of the SM of Cu2+ + Y3+ co-doped ZnO. The
and evenly distributed in the sample. In this case the grains have an average size of 50 nm. The
In this study, pure and Cu2+ + Y3+ co-doped ZnO were synthesized as a function of Cu2+ ion concentration by a solution combustion method. The XRD study showed that the hexagonal wurtzite structure of ZnO is maintained after Cu2+ doping process. Using the (002) plane of XRD spectra, a red shift was observed due to Cu2+ doping process. The PL results for Y3+ doped ZnO showed a UV intensity higher compared with the UV intensity of pure ZnO. For all the Cu2+ ion concentrations, the green PL emission is quenching by Cu2+ doping effect. The UV PL emission can be tailored by Cu2+ doping effect. In 10%wt. of Cu2+ doping, the Y2Cu2O5 phase is created. A blue shift of 0.3 eV is observed in the UV PL emission of Cu2+ + Y3+samples due to Cu2+ doping effect.
The authors wish to thank to Dr. Ciro Falcony (IPN), Adriana Tejeda (IIM) for the XRD measurements, to Omar Novelo Peralta (IIM) for his SEM study, to M.A. Canseco Martinez (IIM) for their chemical analysis.
López-Romero, S., Quiroz-Jiménez, M.J., García-Hipólito, M. and Aguilar-Castillo, A. (2017) Effects of the Cu Ion on the Structural and Optical Properties of Yttrium Doped ZnO by Solution Combustion. World Journal of Condensed Matter Physics, 7, 89-98. https://doi.org/10.4236/wjcmp.2017.74008