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
62 results
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Now showing 1 - 10 of 62
Item Electron beam induced current and remote electron beam induced current assessment of chemical vapor deposited diamond films(Journal of Applied Physics, 1999) Cremades Rodríguez, Ana Isabel; Piqueras de Noriega, JavierIn the present work, electron beam induced current (EBIC) has been applied to characterize several kinds of chemical vapor deposition diamond films. Regions of enhanced carrier recombination are detected in plan-view observations of thin films as well as in cross sections of thick films. Remote EBIC (REBIC) has been applied to obtain information about charged defects present in the samples. The dependence of EBIC and REBIC contrast on the contact configuration used, and on the observation conditions has been analyzed. Cathodoluminescence images of the same samples have been recorded for comparison.Item Luminescence Study of Structural-Changes Induced by Laser Cutting in Diamond Films(Journal of Applied Physics, 1995) Cremades Rodríguez, Ana Isabel; Piqueras de Noriega, JavierThe effect of laser cutting on the structure of a chemical vapor deposited diamond film has been investigated by cathodoluminescence (CL) in the scanning electron microscope. The variation of particle morphology and CL spectra as a function of the distance to the cutting edge is described and possible laser induced structural changes are discussed. At the damaged region total CL emission increases and nitrogen-vacancy centers are detected.Item Cathodoluminescence and REBIC study of defects in tin oxide(24th International Conference on Microelectronics (MIEL 2004), 2004) Maestre Varea, David; Cremades Rodríguez, Ana Isabel; Piqueras de Noriega, JavierCathodoluminescence (CL) and remote electron beam induced current (REBIC) in the scanning electron microscope (SEM) has been used to investigate the electron recombination mechanisms in tin oxide. Sintered material prepared from high purity powder has been found to show a strong dependence of the CL emission on the thermal treatments applied during sample preparation. SEM images show the presence of nano and microcrystalline grains. The correlation of the grain size and morphology with the optical emission is analysed by CL microscopy and spectroscopy. The evolution of the luminescence bands with mechanical milling shows a complex evolution of the 1.94 eV and 2.58 eV emissions which is explained by formation and recovery of defects during milling. REBIC measurements and imaging are used to characterize the formation of a potential barrier at the grain boundaries.Item Luminescence study of thermal treated and laser irradiated Bi_12GeO_20 and Bi_12SiO_20 crystals(Journal of Applied Physics, 1998) Cremades Rodríguez, Ana Isabel; Piqueras de Noriega, Javier; Remón, A.; García, J. A.; Santos, M. T.; Dieguez, E.Changes on the defect structure of Bi12GeO20 (BGO) and Bi12SiO20 (BSO) crystals induced by thermal treatments and laser irradiation have been studied by means of cathodoluminescence in the scanning electron microscope. The results have been compared to those previously reported for untreated and electron irradiated samples and recombination mechanisms responsible for some of the observed luminescence bands are discussed. Annealing of EGO samples causes the appearance of a new luminescence band at about 390 nm. The centers responsible for this band decorate the deformation slip bands in quenched EGO as observed in the cathodoluminescence images. The emission observed in BSO in the same spectral range is quenched during the annealing treatment. The annealing induced reduction of Bi ions to metallic Bi appears to be related to the quenching of a band at 640 nm observed in untreated samples.Item Characterisation of different habits in torch-flame-grown diamond and diamond-like films(Diamond and Related Materials, 1999) Pereira, L..; Pereira, E.; Cremades Rodríguez, Ana Isabel; Piqueras de Noriega, Javier; Jimenez, J.; Bielza, J.M.Diamond and diamond-like films grown by the torch flame method have been analysed by different techniques, namely scanning electron microscopy, Raman spectroscopy, electron paramagnetic resonance and catholuminescence microscopy, in order to investigate the main structural features of the different habits present in the films. A correlation between the observed crystal habits, the defect structure and the formation of diamond and/or diamond-like phases has been established. This enables a general quality assessment of the deposits and their correlation with some features usually observed in carbon filmsItem Effects of transition metal doping on the growth and properties of Rutile TiO_2 nanoparticles(Journal of Physical Chemistry C, 2013) Cristian Vasquez, G.; Andrea Peche-Herrero, M.; Maestre Varea, David; Cremades Rodríguez, Ana Isabel; Ramirez-Castellanos, Julio; María Gonzalez-Calbe, José; Piqueras de Noriega, JavierRutile TiO_2 nanoparticles doped with V, Cr, or Mn ions have been synthesized via a modified Pechini method using polymeric precursors. The final particle sizes range between 20 and 500 nm depending on the selected dopant. The TiO_2 rutile phase has been stabilized in the doped nanoparticles at 650 degrees C. Microstructural analysis shows a good crystallinity and cationic homogeneity of the doped nanoparticles. The cathodoluminescence study of the doped and undoped nanoparticles shows a luminescence signal related to the structural defects of the samples and the presence of dopants. In particular, an intense 1.52 eV emission associated with Ti^3+ interstitials dominates the luminescence of undoped nanoparticles, which also exhibit less intense emissions extending from 2 to 3.4 eV. The presence of V, Cr, or Mn in the rutile TiO_2 nanoparticles induces variations in the associated cathodoluminescence signal which would be useful in order to achieve a deeper understanding of the doping process and spread future optical applications. X-ray photoelectron spectroscopy (XPS) confirmed the presence of Ti^3+ in the near-surface region of the nanoparticles, the concentration of which decreases when doping. The presence of Ti^3+ interstitials related states in the band gap is discussed.Item Indium Tin Oxide micro- and nanostructures grown by thermal treatment of InN/SnO2(Journal of Physical Chemistre C, 2010) Maestre Varea, David; Cremades Rodríguez, Ana Isabel; Gregorati, Luca; Piqueras de Noriega, JavierMixtures of InN and SnO2 powders, with it weight ratio of 10:1, have been used as precursors for the thermal growth of arrow-shaped and other elongated micro- and nanostructures of indium-tin oxide (ITO) containing about 2.6 atom % of Sit. The temperatures used in the process, in the range 650-750 degrees C, favor the decomposition of InN and oxidation of In, with it limited incorporation of Sit in the resulting compound. Arrow-shaped indium-tin oxide structures are obtained and formation of stannates during the process is avoided. X-ray photoelectron spectroscopy indicates that tin incorporates into the In2O3 lattice mainly as Sn4+. Luminescence of the ITO microstructures has been studied by cathodoluminescence in the scanning electron microscope.Item Two-dimensional Zn_k In_2O_(k+3) nanostructures: synthesis, growth mechanism, self-assembly, and luminescence(Journal of Nanoparticle Research, 2013) Bartolomé Vílchez, Javier; Maestre Varea, David; Amati, Mateo; Cremades Rodríguez, Ana Isabel; Piqueras de Noriega, JavierIndium-zinc oxide nanostructures, such as nanosheets, nanobelts, and wires formed by oriented stacks of nanoplates have been grown by a controlled thermal evaporation method without the use of a foreign catalyst. Surface features in the stacked hexagonal nanoplates suggest a dislocation-driven growth mechanism for these structures. A growth model for these stacks is proposed based on changes in velocity growth rate between the outer and the inner part of the plates. Zn incorporation has been investigated by means of energy-dispersive spectroscopy, X-ray photoelectron spectroscopy, and selected area electron diffraction. The formation of Zn_k In_2O_(k+3) ternary compounds has been demonstrated. Cathodoluminescence emission and its correlation with the morphology of the structures and Zn content have been studied.Item Electron beam-induced current imaging of chemical vapor-deposited diamond films(Diamond and Related Materials, 1997) Cremades Rodríguez, Ana Isabel; Piqueras de Noriega, Javier; Schreck, M.Electron beam-induced current (EBIC) is applied to the characterization of chemical vapor-deposited (CVD) diamond films. EBIC contrast shows a strong dependence on the orientation of grains relative to the incident electron beam. This is due to the correspondence between certain faces of the diamond grains and enhanced recombination. Cathodoluminescence (CL) images enable identification of the (100) faces of the epitaxial layers as preferential radiative recombination sites, in agreement with the EBIC contrast shown by these films. The capability of the EBIC technique to study recombination processes with high spatial resolution as compared to CL, is analyzed in this work.Item Indium sulfide and ternary In-S-O nanowires for optoelectronic applications(Microscopy and Microanalysis, 2012) Bartolomé Vílchez, Javier; Maestre Varea, David; Cremades Rodríguez, Ana Isabel; Piqueras de Noriega, Javier