CICFIM de la FCFM-UANL, Mexico
Manuel García Méndez got his PhD at the CICESE-UNAM program in Ensenada, México in 2000. Then, he did a Post-doc staying at the Physics Department, University of Manchester in 2000-2001. From 2001 up to date, he has been a Titular Researcher at the CICFIM in Monterrey, NL México, in which he heads the Thin Film Laboratory.
Electronic, structural and photoluminescence properties of ZnO and Ce-doped ZnO thin films deposited on glass substrates by RF reactive-magnetron sputtering, and post annealed at 300C into an oxygen atmosphere, were investigated using X-ray diffraction (XRD), UV-Visible spectroscopy, XPS and PL measurements. Both films crystalized in wurzite structure with lattice parameters very similar in value to the stress-free standard. Transmittance of both films was high, of about 90% at the visible wavelength region (400-750 nm), with a band gap of Eg=3.23 eV and Eg=3.27 eV for pure and Ce-doped films respectively. The absorption edge of the doped film was shifted to the blue because of the Burstein-Moss effect. XPS spectra showed the coexistence of Ce3+ and Ce4+ ions in a proportion of about 70%:30% into the host ZnO lattice. Both type of ions induce extra electron states that allows multi-emission peaks at the blue-green region. Rearrangement of electronic levels because of added Ce into the ZnO matrix is discussed. Such films with blue-green luminescent properties are promising materials for potential applications in optoelectronic devices.