Prof. Teresa Monteiro Profile

Prof. Teresa Monteiro

at Univ de Aveiro

SPIE Involvement:

Conference Program Committee | Author

Publications (11)

PROCEEDINGS ARTICLE | June 16, 2017

Flame based growth of ZnO nano- and microstructures for advanced optical, multifunctional devices, and biomedical applications (Conference Presentation)

Proc. SPIE. 10248, Nanotechnology VIII

KEYWORDS: Oxides, Carbon, Biomedical optics, Nanostructuring, 3D surface sensing, Metals, Ions, Silicon, Zinc oxide, 3D microstructuring

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The recent flame based growth strategy offers a simple and versatile fabrication of various (one, two, and three-dimensional) nano- and microstructures from different metal oxides (ZnO, SnO2, Fe2O3, etc.) in a desired manner.[1] ZnO structures ranging from nanoscales wires to macroscopic and highly porous 3D interconnected tetrapod networks have been successfully synthesized, characterized and utilized for various applications. The ZnO micro- and nanoneedles grown at walls in silicon trenches showed excellent whispering gallery mode resonances and photocatalytic properties.[2] Using the same strategy, large polycrystalline micro- and nanostructured ZnO platelets can be grown with grains interconnected together via grain boundaries and these grain boundaries exhibit a higher conductivity as compared to individual grains.[3] This flame transport synthesis (FTS) approach offers the growth of a large amount of ZnO tetrapods which have shown interesting applications because of their 3D spatial shape and micro-and nanoscale size, for example, interconnected tetrapods based devices for UV-detection and gas sensing.[4-5] Because of their complex 3D shape, ZnO tetrapods can be used as efficient filler particles for designing self-reporting,[6] and other interesting composites. The nanostructured materials exhibit an important role with respect to advanced biomedical applications as grown ZnO structures have shown strong potentials for antiviral applications.[7] Being mechanically strong and micro-and nanoscale in dimensions, these ZnO tetrapods can be easily doped with other elements or hybridized with various nanoparticles in form of hybrid ZnO tetrapods which are suitable for various multifunctional applications, for example, these hybrid tetrapods showed improved gas sensing properties.[8] The sacrificial nature of ZnO allows the for growth of new tetrapods and 3D network materials for various advanced applications, for example, highly porous and ultra light carbon based Aerographite materials[9] and hollow silicon tetrapods.[10] These carbon based highly porous network can be further utilized for growth of new hybrid 3D nanomaterials, for example, Aerographite- GaN[11] and Aerographite-ZnO[12] for advanced optical and other applications.

PROCEEDINGS ARTICLE | February 26, 2016

Quantum well intermixing and radiation effects in InGaN/GaN multi quantum wells

Proc. SPIE. 9748, Gallium Nitride Materials and Devices XI

KEYWORDS: Quantum wells, Light emitting diodes, Polarization, Optical properties, Annealing, Luminescence, Ions, Nitrogen, Gallium nitride, Ion implantation, Indium gallium nitride, Metalorganic chemical vapor deposition, Radiation effects, Indium nitride, Stereolithography

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PROCEEDINGS ARTICLE | June 1, 2015

Defect luminescence in oxides nanocrystals grown by laser assisted techniques

Proc. SPIE. 9519, Nanotechnology VII

KEYWORDS: Oxides, Nanoparticles, Luminescence, Crystals, Ions, Doping, Zinc oxide, Nanocrystals, Lanthanides, Zirconium dioxide

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Wide band gap oxides, such as ZnO, SnO₂ and ZrO₂, are functional materials with a wide range of applications in several important technological areas such as those including lighting, transparent electronics, sensors, catalysis and biolabeling. Recently, doping and co-doping of oxides with lanthanides have attracted a strong interest for lighting purposes, especially among them nanophosphors for bioassays. Tailoring the crystalline materials physical properties for such applications often requires a well-controlled incorporation of dopants in the material lattice and a comprehensive understanding of their role in the oxides matrices. These undoped or intentionally doped oxides have band gap energies exceeding 3.3 eV at room temperature and are known to exhibit optically active centers that span from the ultraviolet to the near infrared region. Typically, by using photon energy excitation above the materials band gap, high quality undoped materials display narrow emission lines near the band edge due to free and bound-exciton recombination, as well as shallow donor-acceptor recombination pairs. Additionally, broad emission bands are often observed in these wide band gap hosts, hampering some of the desired physical properties for further applications. Recognizing and understanding the role of the dopant-related defects when deliberately introduced in the oxide hosts, as well as their influence on the samples luminescence properties, constitutes a matter of exploitation by the scientific community worldwide. In this work, we investigate the luminescence properties of undoped and lanthanide doped oxide materials grown by laser assisted techniques. Laser assisted flow deposition (LAFD) and pulse laser ablation in liquids (PLAL) were used for the growth of ZnO, SnO₂ and yttria stabilized ZrO₂ (YSZ) micro and nanocrystals with different morphologies, respectively. Regarding the YSZ host, trivalent lanthanide ions were optically activated by in-situ doping and co-doping. The influence of the defect energy states on the optical properties of the different undoped and doped metal oxide hosts is investigated under ultraviolet and infrared excitation by means of photoluminescence and photoluminescence excitation.

PROCEEDINGS ARTICLE | March 24, 2015

Structural, optical, electrical and morphological study of transparent p-NiO/n-ZnO heterojunctions grown by PLD

Proc. SPIE. 9364, Oxide-based Materials and Devices VI

KEYWORDS: Electronics, Transparency, Glasses, Crystals, Scanning electron microscopy, Raman spectroscopy, Transmittance, Transparent conductors, Zinc oxide, Heterojunctions

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PROCEEDINGS ARTICLE | March 8, 2014

Doping of Ga2O3 bulk crystals and NWs by ion implantation

Proc. SPIE. 8987, Oxide-based Materials and Devices V

KEYWORDS: Backscatter, Sensors, Chemical species, Annealing, Crystals, Ions, Doping, Ion implantation, Europium, Picture Archiving and Communication System

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PROCEEDINGS ARTICLE | March 8, 2014

ZnO micro/nanocrystals grown by laser assisted flow deposition

Proc. SPIE. 8987, Oxide-based Materials and Devices V

KEYWORDS: Nanoparticles, Particles, Luminescence, Crystals, Composites, Silver, Scanning electron microscopy, Raman spectroscopy, Zinc oxide, Photomicroscopy

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Laser assisted flow deposition (LAFD) is a very high yield method based on a vapor-solid mechanism, allowing the production of ZnO crystals in a very short time. The LAFD was used in the growth of different morphologies (nanoparticles, tetrapods and microrods) of ZnO micro/nanocrystals and their microstructural characterization confirms the excellent crystallinity of the wurtzite structure. The optical properties of the as-grown ZnO crystals investigated by low temperature photoluminescence (PL) evidence a well-structured near band edge emission (NBE) due to the recombination of free (FX), surface (SX) and donor bound (D⁰X) excitons. Among the most representative emission lines, the 3.31 eV transition was found to occur in the stacking faults-free microrods. The luminescence behavior observed in H passivated samples suggests a closer relationship between this optical center and the presence of surface states. Besides the unintentionally doped micro/nanocrystals, ZnO/Ag and ZnO/carbon nanotubes (CNT) hybrid structures were processed by LAFD. The former aims at the incorporation of silver as a p-type dopant and the latter envisaging photovoltaic applications. Silver-related spherical particles were found to be inhomogeneously distributed at the microrods surface, accumulating at the rods tips and promoting the ZnO nanorods re-nucleation. Despite the fact that energy dispersive X-ray measurements suggest that a fraction of the silver could be incorporated in the ZnO rods, no new related luminescence lines or bands were observed when compared with the as-grown samples. For the case of the ZnO/CNT composites two main approaches were adopted: i) a direct deposition of ZnO particles on the surface of vertically aligned multi-walled carbon nanotubes (VACNTs) forests without employing any additional catalyst and ii) new ZnO/CNT hybrids were developed as buckypaper nanocomposites. The use of the LAFD technique in the first approach preserves the CNTs structure and alignment and avoids the collapse of the VACNTs array, which is a major advantage of this method. On the other hand, LAFD grown ZnO nanoparticles and tetrapods were used to produce ZnO/CNT buckypaper nanocomposites. When compared with the as-grown samples the PL spectra of the composites structures behave differently. For the case of the ZnO/VACNTs no changes on the peak position and spectral shape were observed. Only an enhancement of the overall luminescence was found to occur. On contrary, for the buckypaper nanocomposites notable changes on the spectral shape and peak position were observed, likely due to distinct surface band bending effects for the ZnO nanoparticles and tetrapods embedded in the CNTs.

PROCEEDINGS ARTICLE | March 18, 2013

Prospects on laser processed wide band gap oxides optical materials

Proc. SPIE. 8626, Oxide-based Materials and Devices IV

KEYWORDS: Oxides, Optical fibers, Luminescence, Crystals, Ions, Laser processing, Raman spectroscopy, Zinc oxide, Lanthanides, Zirconium dioxide

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PROCEEDINGS ARTICLE | March 18, 2013

On the origin of strain relaxation in epitaxial CdZnO layers

Proc. SPIE. 8626, Oxide-based Materials and Devices IV

KEYWORDS: Cadmium, Backscatter, Spectroscopy, Crystals, X-ray diffraction, Interfaces, Ions, Zinc, Sapphire, Zinc oxide

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PROCEEDINGS ARTICLE | March 15, 2011

Radiation damage formation and annealing in GaN and ZnO

Proc. SPIE. 7940, Oxide-based Materials and Devices II

KEYWORDS: Argon, Chemical species, Annealing, Luminescence, Ions, Zinc, Gallium nitride, Ion implantation, Erbium, Zinc oxide

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PROCEEDINGS ARTICLE | November 14, 2007

Electro-optical measurements, stability, and physical charge behavior of rare-earth based organic light emitting diode

Proc. SPIE. 6655, Organic Light Emitting Materials and Devices XI

KEYWORDS: Energy efficiency, Organic light emitting diodes, Energy transfer, Ions, Electroluminescence, Terbium, Electro optics, Europium, Telescopic pixel displays, Absorption

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PROCEEDINGS ARTICLE | November 12, 2007

Light emission optimization of europium based complex in multilayer organic light emitting diodes

Proc. SPIE. 6655, Organic Light Emitting Materials and Devices XI

KEYWORDS: Organic light emitting diodes, Interfaces, Ions, Electroluminescence, Aluminum, Bismuth, Electron transport, Europium, Telescopic pixel displays, Instrument modeling

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Showing 5 of 11 publications

Conference Committee Involvement (2)

Nanotechnology VIII

8 May 2017 | Barcelona, Spain

Nanotechnology VII

4 May 2015 | Barcelona, Spain

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