D. Maestre | Universidad Complutense de Madrid (original) (raw)
Papers by D. Maestre
In this work poly(3, 4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT:PSS) dispersed in so... more In this work poly(3, 4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT:PSS) dispersed in solvent (5wt.% Dimethyl sulfoxide DMSO & 0.1wt.% Triton X-100) has been studied in pure form and when functionallized with SnO nanoparticles. A preliminary characterization of bare PEDOT:PSS and romarchite SnO nanoparticles synthesized by hydrolysis were firstly carried out. PEDOT:PSS was deposited on FZ n-Si by spin coating method. The influence of a piranha pre-treatment on the Si surface has been evaluated in this work, as well as the effects due to the presence of SnO nanoparticles in the polymer. After achieving good adhesion and passivation of Si surface, the heterostructure has been characterized systematically by means of Raman spectroscopy using a He-Cd (l = 325 nm) laser as excitation source, atomic force microscopy (AFM), scanning electron microscopy (SEM) and photoluminescence (PL) spectra, and PL image. Spatial homogeneity of the film composition on surface has been achieved. ...
The use of NiO in low-dimensional devices requires appropriate synthesis methods allowing to cont... more The use of NiO in low-dimensional devices requires appropriate synthesis methods allowing to control the morphology, size, and final composition of the as-grown samples in order to improve and broaden the applicability of this material in different fields of research. In this work, a vapor-solid and a hydrothermal method have been employed and evaluated for the fabrication of undoped and Sn doped NiO micro and nanostructures. The presence of Sn favours the growth of microwires, by means of thermal treatments at 1400 °C, while by using a hydrothermal process nanobars and nanoparticles with reduced dimensions were obtained. The chemical method leads to a higher control in the final concentration of Sn incorporated in the NiO lattice. X-ray diffraction confirms the crystalline quality of the obtained products, as well as a texture effects and peak-shift associated with the Sn doping process. Photoluminescence measurements demonstrate an increase in the luminescent signal promoted by Sn...
Materials Letters
Abstract Fabrication of p-n heterostructures in low dimensional structures has been considered on... more Abstract Fabrication of p-n heterostructures in low dimensional structures has been considered one of the most promising strategies to develop optoelectronic devices with enhanced applicability in photocatalysis or solar cells, among other fields of research, although it is still a challenging task. Different approaches have been used in the fabrication of p-n heterostructures, usually involving expensive processing and subsequent growth stages. In this work, NiO/SnO2 heterostructures formed by SnO2 micro and nanowires grown on NiO grains, have been fabricated in a single step following a vapor–solid process which avoids the use of catalyst or external substrates.
Journal of Physics D: Applied Physics
Nano Letters
Single-photon emitting point defects in semiconductors have emerged as strong candidates for futu... more Single-photon emitting point defects in semiconductors have emerged as strong candidates for future quantum technology devices. In the present work, we exploit crystalline particles to investigate relevant defect localizations, emission shifting, and waveguiding. Specifically, emission from 6H-SiC micro-and nanoparticles ranging from 100 nm to 5 μm in size is collected using cathodoluminescence (CL), and we monitor signals attributed to the Si vacancy (V Si) as a function of its location. Clear shifts in the emission wavelength are found for emitters localized in the particle center and at the edges. By comparing spatial CL maps with strain analysis carried out in transmission electron microscopy, we attribute the emission shifts to compressive strain of 2−3% along the particle a-direction. Thus, embedding V Si qubit defects within SiC nanoparticles offers an interesting and versatile opportunity to tune single-photon emission energies while simultaneously ensuring ease of addressability via a self-assembled SiC nanoparticle matrix.
Journal of Materials Science: Materials in Electronics
Materials Today: Proceedings
Nanotechnology
Although rapid progress has been made on silicon-poly(3,4ethylenedioxythiophene)/poly-(styrenesul... more Although rapid progress has been made on silicon-poly(3,4ethylenedioxythiophene)/poly-(styrenesulfonate) (PEDOT:PSS) hybrid solar cells, one of the most important and challenging problem facing the technology is the understanding and control of the interface between the silicon (Si) substrate and the PEDOT:PSS material. In this paper, we present a systematic study of the passivation properties of the Si/PEDOT:PSS interface. We investigate both undoped PEDOT:PSS, as well as PEDOT:PSS functionalized with semiconducting oxide nanomaterials (TiO2 and SnO2). The hybrid compound was deposited at room temperature by spin coating, a potentially lower cost, process time and higher throughput alternative compared with the commonly used vacuum-based techniques. Photoluminescence imaging was used to characterize the electronic properties of the PEDOT:PSS/Si interface. Good surface passivation is achieved by PEDOT:PSS functionalized by the semiconducting oxides. We show that control of the concentration of semiconducting oxide nanoparticles in the polymer is 1 Corresponding author: e-mail: smagulk@ife.no 2 crucial in determining the passivation performance. A charge carrier lifetime of about 275 μs has been achieved when using SnO2 nanoparticles at a concentration of 0.5 wt.% as a filler in the composite film. X-Ray Diffraction (XRD), Scanning Electron Microscopy, High Resolution Transmission Electron Microscopy (HRTEM), Energy Dispersive X-Ray in a SEM, and µ-Raman Spectroscopy has been used for morphological, chemical and structural characterization. Finally, a photovoltaic device based on PEDOT:PSS functionalized with semiconducting oxide nanoparticles has been fabricated and the electrically characterized under both dark and illuminated conditions. KEYWORDS: Silicon surface passivation, PEDOT:PSS, functionalization by SnO2 or TiO2, hybrid material.
Nano Research
In the present work, an alternative application of Li2SnO3 nano-and microstructures as promising ... more In the present work, an alternative application of Li2SnO3 nano-and microstructures as promising candidates for intense white-light-emitting devices without the use of phosphors or complex quantum structures is proposed for the first time, as far as we know.
Physical Review B
Oxygen-containing yttrium hydride thin films exhibit photochromic behavior: transparent thin film... more Oxygen-containing yttrium hydride thin films exhibit photochromic behavior: transparent thin films reversibly switch from a transparent state to a photodarkened state after being illuminated with UV or blue light. From optical spectrophotometry and ellipsometry measurements of the transparent state and photodarkened state, it is concluded that the photochromic effect can be explained by the gradual growth, under illumination, of metallic domains within the initial wideband gap semiconducting lattice. This conclusion is supported by Raman measurements.
Physical Review B
The effects of doubly ionized oxygen vacancies (V O 2+ ) on the electronic structure and charge d... more The effects of doubly ionized oxygen vacancies (V O 2+ ) on the electronic structure and charge distribution in rutile TiO 2 are studied by combining first-principles calculations based on density functional theory and experimental results from x-ray photoelectron and x-ray absorption measurements carried out in synchrotron facilities on rutile TiO 2 nanoparticles. The generalized gradient approximation of the Perdew-Burke-Ernzerhof functional has demonstrated its suitability for the analysis of the V O 2+ defects in rutile TiO 2 . It has been found that the presence of empty electronic states at the conduction band shifted ∼1 eV from t 2g and e g states can be associated with local distortions induced by V O 2+ defects, in good agreement with Gauss-Lorentzian band deconvolution of experimental O K-edge spectra. The asymmetry of t 2g and e g bands at the O-K edge has been associated with V O 2+ , which can enrich the understanding of studies where the presence of these defects plays a key role, as in the case of doped TiO 2 .
AIP Conference Proceedings, 2005
ABSTRACT
Journal of Physics D: Applied Physics, 2014
In this work we report on the growth of Fe 1-x Ga x films by means of the electrodeposition techn... more In this work we report on the growth of Fe 1-x Ga x films by means of the electrodeposition technique in baths containing sodium citrate as an antioxidant agent.
Physics, Chemistry and Application of Nanostructures - Reviews and Short Notes to Nanomeeting-2005, 2005
Sintering of SnO 2 , ZnO and Ga 2 O 3 powders under argon flow leads to the formation of differen... more Sintering of SnO 2 , ZnO and Ga 2 O 3 powders under argon flow leads to the formation of different elongated micro and nanostructures on the sample surface. Nanowires have been grown on the three materials investigated, while in the case of SnO 2, tubes were also obtained. The samples have been characterized by scanning electron microscopy (SEM) and by cathodoluminescence in the SEM. The nanostructures show different luminescence properties than the sample background. The luminescence properties of the elongated structures are discussed.
Nanotechnology, 2014
Sb 2 O 3 microrods with orthorhombic phase were grown by an evaporation-deposition method from a ... more Sb 2 O 3 microrods with orthorhombic phase were grown by an evaporation-deposition method from a pure antimony source and substrate. The incorporation of Cr into the substrate has been found to enhance the growth of thinner rods with high crystalline quality, as is revealed by high resolution transmission electron microscopy (HRTEM). Electric field-induced mechanical resonances of Sb 2 O 3 nanorods were studied by in situ measurements in a scanning electron microscope (SEM). Young's modulus of rods with different lengths and cross-sectional dimensions was calculated from the resonance frequency. The E values for the different rods were in the range of 16-48 GPa. For comparison, Young's moduli of several rods were also measured from the force-displacement curve recorded in an atomic force microscope (AFM). The slight difference between the E values obtained by the resonance and by the AFM techniques is within the accepted experimental error.
Journal of Nanoscience and Nanotechnology, 2008
Titanium oxide nanowires have been grown by thermal treatment of pressed TiN powder under argon o... more Titanium oxide nanowires have been grown by thermal treatment of pressed TiN powder under argon or N2 flow. It has been found that two-step treatments at two different temperatures, 400 degrees C and 800 degrees C, lead to the growth of nanowires all over the sample surface. The nanowires are of single crystalline rutile structure. Energy dispersive X-ray spectroscopy and photoelectron spectroscopy measurements show that the oxide nanostructures contain N from the starting nitride. The mechanism of N incorporation into the oxide and its possible effect on the luminescence are discussed.
Applied Physics Letters, 2014
Electric field induced mechanical resonance of In 2 O 3 microrods are studied by in-situ measurem... more Electric field induced mechanical resonance of In 2 O 3 microrods are studied by in-situ measurements in the chamber of a scanning electron microscope. Young´s moduli of rods with different cross-sectional shapes are calculated from the resonance frequency and a range of values between 131 and 152 GPa are obtained. A quality factor of 1180-3780 is measured from the amplitude-frequency curves, revealing the suitability of In 2 O 3 microrods as micromechanical resonators.
In this work poly(3, 4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT:PSS) dispersed in so... more In this work poly(3, 4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT:PSS) dispersed in solvent (5wt.% Dimethyl sulfoxide DMSO & 0.1wt.% Triton X-100) has been studied in pure form and when functionallized with SnO nanoparticles. A preliminary characterization of bare PEDOT:PSS and romarchite SnO nanoparticles synthesized by hydrolysis were firstly carried out. PEDOT:PSS was deposited on FZ n-Si by spin coating method. The influence of a piranha pre-treatment on the Si surface has been evaluated in this work, as well as the effects due to the presence of SnO nanoparticles in the polymer. After achieving good adhesion and passivation of Si surface, the heterostructure has been characterized systematically by means of Raman spectroscopy using a He-Cd (l = 325 nm) laser as excitation source, atomic force microscopy (AFM), scanning electron microscopy (SEM) and photoluminescence (PL) spectra, and PL image. Spatial homogeneity of the film composition on surface has been achieved. ...
The use of NiO in low-dimensional devices requires appropriate synthesis methods allowing to cont... more The use of NiO in low-dimensional devices requires appropriate synthesis methods allowing to control the morphology, size, and final composition of the as-grown samples in order to improve and broaden the applicability of this material in different fields of research. In this work, a vapor-solid and a hydrothermal method have been employed and evaluated for the fabrication of undoped and Sn doped NiO micro and nanostructures. The presence of Sn favours the growth of microwires, by means of thermal treatments at 1400 °C, while by using a hydrothermal process nanobars and nanoparticles with reduced dimensions were obtained. The chemical method leads to a higher control in the final concentration of Sn incorporated in the NiO lattice. X-ray diffraction confirms the crystalline quality of the obtained products, as well as a texture effects and peak-shift associated with the Sn doping process. Photoluminescence measurements demonstrate an increase in the luminescent signal promoted by Sn...
Materials Letters
Abstract Fabrication of p-n heterostructures in low dimensional structures has been considered on... more Abstract Fabrication of p-n heterostructures in low dimensional structures has been considered one of the most promising strategies to develop optoelectronic devices with enhanced applicability in photocatalysis or solar cells, among other fields of research, although it is still a challenging task. Different approaches have been used in the fabrication of p-n heterostructures, usually involving expensive processing and subsequent growth stages. In this work, NiO/SnO2 heterostructures formed by SnO2 micro and nanowires grown on NiO grains, have been fabricated in a single step following a vapor–solid process which avoids the use of catalyst or external substrates.
Journal of Physics D: Applied Physics
Nano Letters
Single-photon emitting point defects in semiconductors have emerged as strong candidates for futu... more Single-photon emitting point defects in semiconductors have emerged as strong candidates for future quantum technology devices. In the present work, we exploit crystalline particles to investigate relevant defect localizations, emission shifting, and waveguiding. Specifically, emission from 6H-SiC micro-and nanoparticles ranging from 100 nm to 5 μm in size is collected using cathodoluminescence (CL), and we monitor signals attributed to the Si vacancy (V Si) as a function of its location. Clear shifts in the emission wavelength are found for emitters localized in the particle center and at the edges. By comparing spatial CL maps with strain analysis carried out in transmission electron microscopy, we attribute the emission shifts to compressive strain of 2−3% along the particle a-direction. Thus, embedding V Si qubit defects within SiC nanoparticles offers an interesting and versatile opportunity to tune single-photon emission energies while simultaneously ensuring ease of addressability via a self-assembled SiC nanoparticle matrix.
Journal of Materials Science: Materials in Electronics
Materials Today: Proceedings
Nanotechnology
Although rapid progress has been made on silicon-poly(3,4ethylenedioxythiophene)/poly-(styrenesul... more Although rapid progress has been made on silicon-poly(3,4ethylenedioxythiophene)/poly-(styrenesulfonate) (PEDOT:PSS) hybrid solar cells, one of the most important and challenging problem facing the technology is the understanding and control of the interface between the silicon (Si) substrate and the PEDOT:PSS material. In this paper, we present a systematic study of the passivation properties of the Si/PEDOT:PSS interface. We investigate both undoped PEDOT:PSS, as well as PEDOT:PSS functionalized with semiconducting oxide nanomaterials (TiO2 and SnO2). The hybrid compound was deposited at room temperature by spin coating, a potentially lower cost, process time and higher throughput alternative compared with the commonly used vacuum-based techniques. Photoluminescence imaging was used to characterize the electronic properties of the PEDOT:PSS/Si interface. Good surface passivation is achieved by PEDOT:PSS functionalized by the semiconducting oxides. We show that control of the concentration of semiconducting oxide nanoparticles in the polymer is 1 Corresponding author: e-mail: smagulk@ife.no 2 crucial in determining the passivation performance. A charge carrier lifetime of about 275 μs has been achieved when using SnO2 nanoparticles at a concentration of 0.5 wt.% as a filler in the composite film. X-Ray Diffraction (XRD), Scanning Electron Microscopy, High Resolution Transmission Electron Microscopy (HRTEM), Energy Dispersive X-Ray in a SEM, and µ-Raman Spectroscopy has been used for morphological, chemical and structural characterization. Finally, a photovoltaic device based on PEDOT:PSS functionalized with semiconducting oxide nanoparticles has been fabricated and the electrically characterized under both dark and illuminated conditions. KEYWORDS: Silicon surface passivation, PEDOT:PSS, functionalization by SnO2 or TiO2, hybrid material.
Nano Research
In the present work, an alternative application of Li2SnO3 nano-and microstructures as promising ... more In the present work, an alternative application of Li2SnO3 nano-and microstructures as promising candidates for intense white-light-emitting devices without the use of phosphors or complex quantum structures is proposed for the first time, as far as we know.
Physical Review B
Oxygen-containing yttrium hydride thin films exhibit photochromic behavior: transparent thin film... more Oxygen-containing yttrium hydride thin films exhibit photochromic behavior: transparent thin films reversibly switch from a transparent state to a photodarkened state after being illuminated with UV or blue light. From optical spectrophotometry and ellipsometry measurements of the transparent state and photodarkened state, it is concluded that the photochromic effect can be explained by the gradual growth, under illumination, of metallic domains within the initial wideband gap semiconducting lattice. This conclusion is supported by Raman measurements.
Physical Review B
The effects of doubly ionized oxygen vacancies (V O 2+ ) on the electronic structure and charge d... more The effects of doubly ionized oxygen vacancies (V O 2+ ) on the electronic structure and charge distribution in rutile TiO 2 are studied by combining first-principles calculations based on density functional theory and experimental results from x-ray photoelectron and x-ray absorption measurements carried out in synchrotron facilities on rutile TiO 2 nanoparticles. The generalized gradient approximation of the Perdew-Burke-Ernzerhof functional has demonstrated its suitability for the analysis of the V O 2+ defects in rutile TiO 2 . It has been found that the presence of empty electronic states at the conduction band shifted ∼1 eV from t 2g and e g states can be associated with local distortions induced by V O 2+ defects, in good agreement with Gauss-Lorentzian band deconvolution of experimental O K-edge spectra. The asymmetry of t 2g and e g bands at the O-K edge has been associated with V O 2+ , which can enrich the understanding of studies where the presence of these defects plays a key role, as in the case of doped TiO 2 .
AIP Conference Proceedings, 2005
ABSTRACT
Journal of Physics D: Applied Physics, 2014
In this work we report on the growth of Fe 1-x Ga x films by means of the electrodeposition techn... more In this work we report on the growth of Fe 1-x Ga x films by means of the electrodeposition technique in baths containing sodium citrate as an antioxidant agent.
Physics, Chemistry and Application of Nanostructures - Reviews and Short Notes to Nanomeeting-2005, 2005
Sintering of SnO 2 , ZnO and Ga 2 O 3 powders under argon flow leads to the formation of differen... more Sintering of SnO 2 , ZnO and Ga 2 O 3 powders under argon flow leads to the formation of different elongated micro and nanostructures on the sample surface. Nanowires have been grown on the three materials investigated, while in the case of SnO 2, tubes were also obtained. The samples have been characterized by scanning electron microscopy (SEM) and by cathodoluminescence in the SEM. The nanostructures show different luminescence properties than the sample background. The luminescence properties of the elongated structures are discussed.
Nanotechnology, 2014
Sb 2 O 3 microrods with orthorhombic phase were grown by an evaporation-deposition method from a ... more Sb 2 O 3 microrods with orthorhombic phase were grown by an evaporation-deposition method from a pure antimony source and substrate. The incorporation of Cr into the substrate has been found to enhance the growth of thinner rods with high crystalline quality, as is revealed by high resolution transmission electron microscopy (HRTEM). Electric field-induced mechanical resonances of Sb 2 O 3 nanorods were studied by in situ measurements in a scanning electron microscope (SEM). Young's modulus of rods with different lengths and cross-sectional dimensions was calculated from the resonance frequency. The E values for the different rods were in the range of 16-48 GPa. For comparison, Young's moduli of several rods were also measured from the force-displacement curve recorded in an atomic force microscope (AFM). The slight difference between the E values obtained by the resonance and by the AFM techniques is within the accepted experimental error.
Journal of Nanoscience and Nanotechnology, 2008
Titanium oxide nanowires have been grown by thermal treatment of pressed TiN powder under argon o... more Titanium oxide nanowires have been grown by thermal treatment of pressed TiN powder under argon or N2 flow. It has been found that two-step treatments at two different temperatures, 400 degrees C and 800 degrees C, lead to the growth of nanowires all over the sample surface. The nanowires are of single crystalline rutile structure. Energy dispersive X-ray spectroscopy and photoelectron spectroscopy measurements show that the oxide nanostructures contain N from the starting nitride. The mechanism of N incorporation into the oxide and its possible effect on the luminescence are discussed.
Applied Physics Letters, 2014
Electric field induced mechanical resonance of In 2 O 3 microrods are studied by in-situ measurem... more Electric field induced mechanical resonance of In 2 O 3 microrods are studied by in-situ measurements in the chamber of a scanning electron microscope. Young´s moduli of rods with different cross-sectional shapes are calculated from the resonance frequency and a range of values between 131 and 152 GPa are obtained. A quality factor of 1180-3780 is measured from the amplitude-frequency curves, revealing the suitability of In 2 O 3 microrods as micromechanical resonators.