Ponente
Descripción
Photoluminescence (PL) is the emission of light from a material whose electrons have been previously excited by photon absorption. Subsequently, the electrons recombine through optical transitions that involve defect levels, traps, and the valence band. PL is a phenomenon that basically occurs in the superficial region. ZnO is a semiconductor widely studied for its relevant characteristics. ZnO has n-type conductivity due to defects such as O and Zn vacancies and that they are also interstitial in ZnO lattice. The PL spectrum of ZnO is usually observed as a peak at around 3.24 eV related to a transition due to excitonic collision and a broad band in the region between 1.5 and 3.0 eV related to defects. However, it must be taken into account that the transitions within the material are not the same as those on the surface, which is much more defective. In the present work, measures of the PL spectra of ZnO nanoparticles dispersed in water, which partially passivates the surface, were carried out in order to attain an approach to the elucidation of the internal transitions. The behavior of the non-doped and doped ZnO PL spectra with various concentrations of Co and Cr is analyzed. A comparison is made with the PL spectra measured directly on ZnO:Cr nanoparticles, which shows the enormous influence of the surface.
