Caracterización microestructural de láminas de diamante por técnicas de inyección de haces

Tesis de la Universidad Complutense de Madrid, Facultad de Ciencias Físicas, Departamento de Física de Materiales, leída el 25-10-1996En el trabajo de investigación desarrollado en esta tesis doctoral se han caracterizado láminas de diamante crecidas mediante deposición química a partir de fase vapor (cvd) mediante catadoluminiscencia (cl), fotoluminiscencia con resolución temporal (trpl), raman, electroluminiscencia (el), y corriente inducida por el haz de electrones de un microscopio electrónico de barrido (ebic). Se han estudiado en detalle láminas sin tratar, correlacionando los resultados de las medidas con los parámetros de la deposición y la estructura de defectos de las láminas. Asimismo, se ha prestado atención al efecto de la irradiación con láser sobre la luminiscencia de las láminas. Con ebic y el se han estudiado las propiedades de recombinación de portadores. Como complemento al estudio del diamante, se han incluido algunos resultados sobre la luminiscencia de laminas epitaxiales de gan.Depto. de Física de MaterialesFac. de Ciencias FísicasTRUEpu

Cathodoluminescence of defects in sintered tin oxide

Cathodoluminescence (CL) in the scanning electron microscope (SEM) has been used to investigate the luminescence 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 analyzed by CL microscopy and spectroscopy. The main emission bands appear centered at about 2.58, 2.25, and 1.94 eV depending on the sintering treatment. CL images reveal that the 2.25 and the 2.58 eV bands are associated at specific crystal faces. The evolution of the luminescence bands with mechanical milling shows a complex evolution of the 1.94 and 2.58 eV emissions which is explained by formation and recovery of defects during milling

Cathodoluminescence and REBIC study of defects in tin oxide

Cathodoluminescence (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

Editorial: Topical issue "Nanomaterials for energy- and environment-related applications"

© Elsevier Ltd. Available online 26 May 2020. Symposium on Metal Oxide-and Oxyhydride-Based Nanomaterials for Energy and Environment-Related Applications of the E-MRS (2019. Varsovia)Depto. de Física de MaterialesFac. de Ciencias FísicasTRUEpu

Temperature-dependent photoluminescence of anatase Li-doped TiO_(2) nanoparticles

TiO_(2) is currently one of the most employed material in photocatalysis and optoelectronic applications. By doping with different elements, tailored luminescent and optoelectronic properties can be obtained, which further enhances its applicability. The achievement of deeper knowledge and control on the recombination processes via light-metal doping engineering promises a wider use in optoelectronic applications. In this work, the luminescent properties of undoped and Li-doped anatase TiO_(2) nanoparticles obtained by hydrolysis process are studied, by means of photoluminescence (PL) measurements from 10 K to room-temperature. TiO_(2) presents a wide emission which covers the visible range, while Li-doping quenches the emission on the low visible region. By terms of time-resolved luminescence (TR-PL), lifetime of the recombination processes can be obtained, in which a decrease on lifetime values can be observed for the doped samples

An approach to emerging optical and optoelectronic applications based on NiO micro- and nanostructures

Nickel oxide (NiO) is one of the very few p-type semiconducting oxides, the study of which is gaining increasing attention in recent years due to its potential applicability in many emerging fields of technological research. Actually, a growing number of scientific works focus on NiO-based electrochromic devices, high-frequency spintronics, fuel cell electrodes, supercapacitors, photocatalyst, chemical/gas sensors, or magnetic devices, among others. However, less has been done so far in the development of NiO-based optical devices, a field in which this versatile transition metal oxide still lags in performance despite its potential applicability. This review could contribute with novelty and new forefront insights on NiO micro and nanostructures with promising applicability in optical and optoelectronic devices. As some examples, NiO lighting devices, optical microresonators, waveguides, optical limiters, and neuromorphic applications are reviewed and analyzed in this work. These emerging functionalities, together with some other recent developments based on NiO micro and nanostructures, can open a new field of research based on this p-type material which still remains scarcely explored from an optical perspective, and would pave the way to future research and scientific advances

Synthesis of In_2S_3 and In_6S_7 microcolumns and nanowires by a vapor-solid method

Indium sulfide (In_2S_3) is a promising candidate for the replacement of CdS buffer layers in solar cell devices, while hexaindium heptasulfide (In_6S_7) presents interesting properties for its use as absorber material. In this work the fabrication of In_2S_3 microcolumns as well as novel In_6S_7 nanowires with diameters of about 70-120nm is reported. The structures are grown following a thermal evaporation-deposition method at temperatures between 900 and 1000º C. Control of the phase and morphology of the structures is achieved through both the evaporation and deposition temperatures, which can be tuned separately. Energy dispersive spectroscopy shows no traces of residual oxygen, while X-ray photoelectron spectroscopy indicates the presence of small amounts of oxygen incorporated at the surface of the structures. The In_6S_7 nanowires are found to be degenerated n-type semiconductors, with the Fermi level above the conduction band minimum. The origin of this n-type degeneracy is discussed in terms of S vacancies

Growth and characterization of SnO_2 micro- and nanotubes

Micro- and nanotubes, and other elongated structures of SnO_2 as wires and rods, were grown after sintering in argon flow at temperatures ranging from 1350 degrees C to 1500 degrees C. The morphology and luminescence properties of these structures have been investigated by means of the secondary electron and the cathodoluminescence (CL) modes of the scanning electron microscope (SEM)

In situ local oxidation of SnO induced by laser irradiation: a stability study

In this work, semiconductor tin oxide (II) (SnO) nanoparticles and plates were synthesized at room conditions via a hydrolysis procedure. X-ray diffraction (XRD) and transmission electron microscopy (TEM) confirmed the high crystallinity of the as-synthesized romarchite SnO nanoparticles with dimensions ranging from 5 to 16 nm. The stability of the initial SnO and the controlled oxidation to SnO_2 was studied based on either thermal treatments or controlled laser irradiation using a UV and a red laser in a confocal microscope. Thermal treatments induced the oxidation from SnO to SnO2 without formation of intermediate SnO_x, as confirmed by thermodiffraction measurements, while by using UV or red laser irradiation the transition from SnO to SnO_2 was controlled, assisted by formation of intermediate Sn3O4, as confirmed by Raman spectroscopy. Photoluminescence and Raman spectroscopy as a function of the laser excitation source, the laser power density, and the irradiation duration were analyzed in order to gain insights in the formation of SnO_2 from SnO. Finally, a tailored spatial SnO/SnO_2 micropatterning was achieved by controlled laser irradiation with potential applicability in optoelectronics and sensing devices