Investigation of defect related luminescence of Ti doped ZnO Nanoparticles

The effects of surface defect (oxygen vacancies) on the electronic structure and photoluminance properties of the titanium doped ZnO nanoparticles are investigated in this paper. Nanoparticles of different sizes ranging from 6 to 25nm were characterized by x-ray diffraction (XRD), Transmission electron micrograph, x-ray photoemission emission spectroscopy (XPS) and photoluminescence (PL) spectra. Structural analysis (including XRD, TEM and HR-TEM) and electronic studies (via XPS) indicate that the Ti ions are well substituted for the Zn ions in the ZnO matrix. Surface defects systemically increase, as manifested by the Zn2p core level of XPS measurements, with decreasing particles size and it further confirmed via Raman scattering measurements. The intensity of the visible peak in PL spectra exhibits an apparent non change over the entire range of particle size. It is found that the intensity first decreases with increasing particle size but increases above a typical size (15nm). This non-monotonic profile of visible intensity could be explained via two different mechanisms, where intensity changes from being followed by hole-trapped tunneling in lower size particles to being followed by increasing surface depletion region, containing rich amount of doubly charged oxygen vacancy(Vo 2+),in the bigger size particle.

کلیدواژه ها:

Doped ZnO ، Nanoparticles ، Photoluminescence ، Surface States