Investigations On The Growth And Property Of Cu Doped ZnO Nanoparticles

Zinc oxide (ZnO) is a direct wide band gap (3.37eV) semiconductor with a relatively exciton binding energy (60meV). Zn0 has been widely used in catalysis, solar cells and gas sensor due to its excellent optical and electrical properties. It can utilize both of charge and spin of an electron simultaneously in hopes of being applied into the novel electronic materials and devices, so it is attracting people's more and more attention. On the other hand, nanostructured Zn0 has a diverse of growth morphologies, which is regarded as the richest family among all the nanomaterials. Zn0 nanostructures promising potentials in extensive applications and are the essential building blocks for fabricating nano-optoelectronics and nano-electronics device, nanosized gas sensors, transducers, and field emitters etc.Cu doped ZnO nano particles are synthesize on sol-gel method. The structure was identified and the growth mechanism was also studied. Then a research was done about the effect of dopant on the properties of the optical and magnetic properties. The main results are as follows:1.With the sol-gel method ,the synthesis of hexagonal ZnO nanoparticles doped by different concentrations of Cu was synthesis, and the doping concentration of Cu was increased to 8% without the second phase. The composition distributions characterized by an energy dispersive x-ray spectrometer (EDX) mapping showed that besides the O element, there are only Zn and Cu element. The surface compositions and valence state characterized by x-ray photoelectron spectroscopy (XPS) analysis showed that the valence state was changed when the concentration of dopant were changed. Both field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM) image imply that these nanoparticles have an average diameter of 18 nm.The shape and size of these particles were uniform. The particles were compact agglomerate and uniform,which is due to the growth mechanism of ZnO.2.The ultraviolet-visible absorption (UV)spectra show that the absorption edge cut off between 370 and 390nm.The increase of the dopant leaded to red shift, an absorption bandwith increased and an intensity decrease. We measured photoluminescence (PL) spectra and investigated that Zn98Cu2O exhibited an emission peak at 400nm.3.To investigation of magnetic property, we measured VSM. Ferromagnetism is observed in Zn1-xCuxO nanoparticles. We hypothesize that the delocalized holes induced by O 2p can be strongly hybridized with the localized unoccupied twofold t2 subband of Cu 3d states to yield bound magnetic polarons. Then, a spin-split acceptor impurity band is created at the top of the valence band, hence giving rise to the macroscopic FM.