Person: Cremades Rodríguez, Ana Isabel
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First Name
Ana Isabel
Last Name
Cremades Rodríguez
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Físicas
Department
Area
Ciencia de los Materiales e Ingeniería Metalúrgica
Identifiers
4 results
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Now showing 1 - 4 of 4
Item The effect of annealing in different atmospheres on the luminescence of polycrystalline TiO_2(Journal of Physics: Condensed Mater, 2004) Plugaru, R; Cremades Rodríguez, Ana Isabel; Piqueras De Noriega, Francisco JavierPolycrystalline samples of titanium oxide were prepared by thermal sintering, in argon and air atmospheres at temperatures ranging from 1100 to 1500 degreesC, from powders of anatase and rutile phases. The samples sintered in argon were further treated in oxygen at the temperature of 800 degreesC for intervals of time up to 8 h. The luminescence emission of the initial powders was situated in the green region, with the peak at 580 nm. The sintering treatment in argon leads to a decrease of the luminescence intensity that appears as a broad band peaked at 550 nm in the case of anatase and as a band peaked at 450 nm in the case of the rutile phase. The sintering treatment in air causes the quenching of the emission in the visible region. In both cases, a sharp and intense emission appears in the infrared region at 800 nm for rutile and 820 nm for the anatase phase. The blue emission is sensitive to the treatment in oxygen atmosphere which causes mainly an intensity increase of the band at 450 nm. The treatment in oxygen results in the reconstruction of the polycrystalline sample surface as hexagonal shape protrusions and large terraces.Item Cathodoluminescence from nanocrystalline silicon films in the scanning electron microscope(Solided State phenomena, 1998) Méndez Martín, María Bianchi; Piqueras De Noriega, Francisco Javier; Plugaru, R; Craciun, G.; Nastase, N.; Cremades Rodríguez, Ana Isabel; Nogales Díaz, EmilioLuminescence emission of nanocrystalline silicon films has been studied by cathodoluminescence (CL) in the scanning electron microscope. As deposited films show visible luminescence with dominant blue band as well as a red band. The evolution of CL bands after implantation and anodization treatments is investigated. Our results suggest that the dominant blue band has a complex character with a component at 400 nm which appears related to quantum size effects.Item Effect of thermal and mechanical treatments on the cathodoluminescence of tin and titanium oxides(Spatially resolved characterization of local phenomena in materials and nanostructures, 2003) Maestre Varea, David; Plugaru, R; Cremades Rodríguez, Ana Isabel; Piqueras De Noriega, Francisco JavierThe luminescence of titanium oxide and tin oxide has been investigated by cathodoluminescence in the SEM, as a function of the structural changes induced by thermal treatments. The evolution of the luminescence of TiO2 rutile, anatase and mixture phase with the annealing temperature is related to the process of thermal induced grain texture and to transition of metastables phases to the stable rutile. The emission band is peaked at 480 nm for the composite phase and at 580 nm for anatase and rutile phases respectively. A broad band in the 520-560 nm region is present in the spectra of both anatase and rutile phase. Thermal annealing leads to a red shift of the luminescence emission, with the emission band peaked at around 820 nm. In sintered tin oxide the main emission bands appear centered at about 480 nm and 630 nm. The intensity of these bands increases with annealing temperature up to 1200degreesC, whereas for samples annealed at 1500degreesC these emissions are quenched. Mechanical ball milling has been used to produce nanocrystalline SnO_2 grains to investigate the influence of the presence of nanocrystals on the CL emission.Item Growth of titanium oxide nanorods(CAS 2005: International Semiconductor Conference, 2005) Plugaru, R; Cremades Rodríguez, Ana Isabel; Piqueras De Noriega, Francisco JavierNanorods of titanium oxide (TiO_2) were obtained by thermally activated growth process carried out on pellets of nanocrystalline powder with mixed anatase and rutile structures. The nanostuctured array consists of nanorods with length between 300 min and 1 mu m and hexagonal cross section of 100-200 nm diameter. Herein it is shown that one can obtain information on the nanostructure growth from cathodoluminescence emission spectra. Vie growth process of the rods is mainly associated with the presence of the anatase phase. The keyrole of characteristic defects in semiconductor oxides, namely oxygen vacancies and Ti_(n+) ions is discussed.