Francesca Peiro | University of Barcelona (original) (raw)
Papers by Francesca Peiro
![Research paper thumbnail of {"__content__"=>"Surface Chemistry and Nano-/Microstructure Engineering on Photocatalytic InS Nanocrystals.", "sub"=>[{"__content__"=>"2"}, {"__content__"=>"3"}]}](https://attachments.academia-assets.com/70299403/thumbnails/1.jpg)
](Langmuir : the ACS journal of surfaces and colloids, Jan 5, 2018
Colloidal nanocrystals (NCs) compete with molecular catalysts in the field of homogenous catalysi... more Colloidal nanocrystals (NCs) compete with molecular catalysts in the field of homogenous catalysis, offering easier recyclability and a number of potentially advantageous functionalities, such as tunable band gaps, plasmonic properties, or a magnetic moment. Using high-throughput printing technologies, colloidal NCs can also be supported onto substrates to produce cost-effective electronic, optoelectronic, electrocatalytic, and sensing devices. For both catalytic and technological application, NC surface chemistry and supracrystal organization are key parameters determining final performance. Here, we study the influence of the surface ligands and the NC organization on the catalytic properties of InS, both as a colloid and as a supported layer. As a colloid, NCs stabilized by inorganic ligands show the highest photocatalytic activities, which we associate with their large and more accessible surfaces. On the other hand, when NCs are supported on a substrate, their organization beco...
ACS Applied Materials & Interfaces
Nanoscale research letters, 2017
Recently, colored H-doped TiO2 (H-TiO2) has demonstrated enhanced photoelectrochemical (PEC) perf... more Recently, colored H-doped TiO2 (H-TiO2) has demonstrated enhanced photoelectrochemical (PEC) performance due to its unique crystalline core-disordered shell nanostructures and consequent enhanced conduction behaviors between the core-shell homo-interfaces. Although various hydrogenation approaches to obtain H-TiO2 have been developed, such as high temperature hydrogen furnace tube annealing, high pressure hydrogen annealing, hydrogen-plasma assisted reaction, aluminum reduction and electrochemical reduction etc., there is still a lack of a hydrogenation approach in a controlled manner where all processing parameters (temperature, time and hydrogen flux) were precisely controlled in order to improve the PEC performance of H-TiO2 and understand the physical insight of enhanced PEC performance. Here, we report for the first time a controlled and local rapid thermal annealing (RTA) approach to prepare hydrogenated core-shell H-TiO2 nanorods grown on F:SnO2 (FTO) substrate in order to ad...
Nano letters, Aug 8, 2016
The physicochemical properties used in numerous advanced nanostructured devices are directly cont... more The physicochemical properties used in numerous advanced nanostructured devices are directly controlled by the oxidation states of their constituents. In this work we combine electron energy-loss spectroscopy, blind source separation, and computed tomography to reconstruct in three dimensions the distribution of Fe(2+) and Fe(3+) ions in a FeO/Fe3O4 core/shell cube-shaped nanoparticle with nanometric resolution. The results highlight the sharpness of the interface between both oxides and provide an average shell thickness, core volume, and average cube edge length measurements in agreement with the magnetic characterization of the sample.
Journal of Vacuum Science Technology B Microelectronics and Nanometer Structures, 1997
ABSTRACT In this work, we present a correlation between the morphological characterization of Iny... more ABSTRACT In this work, we present a correlation between the morphological characterization of InyAl1-yAs/InxGa1-xAs heterostructures grown on InP substrates for high electron mobility transistors (HEMTs) applications as determined by transmission electron microscopy, and the electrical behavior of the two-dimensional electron gas (2DEG) confined in the InGaAs channel. Our main goal is to analyze the origin of the low and anisotropic values of 2DEG Hall mobilities, discussing the effect of the density and asymmetric distribution of stacking faults and the surface undulation induced by a three-dimensional (3D) growth mode, depending on the growth temperature (Tg) and thickness (tw) of the InxGa1-xAs well. Our results have shown that a high mobility for a matched channel is obtained if the In0.53Ga0.47As layer is grown at 530 °C. Lower temperatures reduce the mobility values and lead to higher mobilities for [11¯0] due to the surface corrugation along [110] induced by lateral decomposition of the InGaAs at low growth temperatures. For HEMT structures with strained In0.75Ga0.25As channels grown at 530 °C, within the range of the well thickness considered (5–10 nm), Hall mobilities are also more influenced by the surface roughness than by fault distribution. However, in this case, the observed roughness is not driven by alloy decomposition but by a strain-induced 3D growth mode. © 1997 American Vacuum Society.
Microscopy and microanalysis : the official journal of Microscopy Society of America, Microbeam Analysis Society, Microscopical Society of Canada, Jan 12, 2016
In the present work, the dielectric response of III-nitride semiconductors is studied using densi... more In the present work, the dielectric response of III-nitride semiconductors is studied using density functional theory (DFT) band structure calculations. The aim of this study is to improve our understanding of the features in the low-loss electron energy-loss spectra of ternary alloys, but the results are also relevant to optical and UV spectroscopy results. In addition, the dependence of the most remarkable features with composition is tested, i.e. applying Vegard's law to band gap and plasmon energy. For this purpose, three wurtzite ternary alloys, from the combination of binaries AlN, GaN, and InN, were simulated through a wide compositional range (i.e., Al x Ga1-x N, In x Al1-x N, and In x Ga1-x N, with x=[0,1]). For this DFT calculations, the standard tools found in Wien2k software were used. In order to improve the band structure description of these semiconductor compounds, the modified Becke-Johnson exchange-correlation potential was also used. Results from these calcula...
Crystal Growth Design, 2009
Investigations on shape and chemical composition of one-dimensional magnetite nanostructures grow... more Investigations on shape and chemical composition of one-dimensional magnetite nanostructures grown by a catalyst-assisted vapor phase procedure are reported. Intrinsic crystal chemistry (preferred growth of most stable surfaces) could be modulated by seeding the magnetite ...
Springer Proceedings in Physics, 2008
ABSTRACT
ACS Applied Materials & Interfaces, 2015
(001)-Epitaxial La2WO6 (LWO) thin films are grown by pulsed laser deposition on (001)-oriented Sr... more (001)-Epitaxial La2WO6 (LWO) thin films are grown by pulsed laser deposition on (001)-oriented SrTiO3 (STO) substrates. The α-phase (high-temperature phase in bulk) is successfully stabilized with an orthorhombic structure (a = 16.585(1) Å, b = 5.717(2) Å, c = 8.865(5) Å). X-ray-diffraction pole-figure measurements suggest that crystallographic relationships between the film and substrate are [100]LWO ∥ [110]STO, [010]LWO ∥ [11̅0]STO and [001]LWO ∥ [001]STO. From optical properties, investigated by spectroscopic ellipsometry, we extract a refractive-index value around 2 (at 500 nm) along with the presence of two absorption bands situated, respectively at 3.07 and 6.32 eV. Ferroelectricity is evidenced as well on macroscale (standard polarization measurements) as on nanoscale, calling for experiments based on piezo-response force-microscopy, and confirmed with in situ scanning-and-tunneling measurements performed with a transmission electron microscope. This work highlights the ferroelectric behavior, at room temperature, in high-temperature LWO phase when stabilized in thin film and opens the way to new functional oxide thin films dedicated to advanced electronic devices.
Chemistry of Materials, 2015
2009 Spanish Conference on Electron Devices, 2009
(S) TEM tomography is used as a complementary tool to characterize AlAs-GaAs coaxial nanowires. T... more (S) TEM tomography is used as a complementary tool to characterize AlAs-GaAs coaxial nanowires. These nanostructures have been grown on two different GaAs substrate orientations using molecular-beam epitaxy (MBE). The results show that quantum wells synthesized on nanowires grown on different substrate orientations present different morphology, which induces changes on their photoluminescence properties.
Thin Solid Films, 2000
MgF2 is a current material for the optical applications in the UV and deep UV range. Nevertheless... more MgF2 is a current material for the optical applications in the UV and deep UV range. Nevertheless, modern applications still require improvement of the optical and structural quality of the deposited layers. In the present work, the composition and microstructure of MgF2 single layers grown on Si [100] substrate by physical vapour deposition (PVD) and ion beam sputtering (IBS) processes,
The Journal of Physical Chemistry C, 2012
ABSTRACT Microwave-assisted chemistry is becoming very attractive in all areas of synthetic chemi... more ABSTRACT Microwave-assisted chemistry is becoming very attractive in all areas of synthetic chemistry; it is fast, easy to operate, efficient in terms of energy consumption and environmentally friendly. However, a quantitative assessment of this chemical procedure with respect to other widely used chemical routes is lacking. Focusing in the preparation of iron oxide nanoparticles of comparable sizes, we have analyzed the performance of microwave-assisted synthesized nanoparticles compared to those obtained by the widespread thermal decomposition process of metal complexes. On the basis of a multidisciplinary experimental approach, we have unveiled that microwave-synthesized nanoparticles exhibit a surface reactivity significantly smaller than their thermal decomposition counterparts. We ascribe such dissimilarities to the different configurations of crystallographic faceting planes resulting from the particularities of both synthesis routes. We also show that the microwave route allows a direct stabilization of the particles in organic or aqueous media by using either steric or electrostatic stabilizers. A simplified life cycle analysis, as a preliminary framework toward nanoparticles eco-design, shows also a cost-effective positive balance for the microwave synthesis. Our results are of relevance for a broad range of applications including health, information storage, environmental remediation, sensors, or catalysis.
physica status solidi (a), 2003
ABSTRACT The influence of different technological parameters on the development of compositional ... more ABSTRACT The influence of different technological parameters on the development of compositional and morphological instabilities in InAlAs and InGaAs layers grown on InP substrates is studied in the present work by transmission electron microscopy (TEM). Results show that substrate misorientation plays a decisive role in the decomposition of strained layers. It is illustrated that the modulation of composition due to the layer morphological instability is a thermally activated process. The influence of lattice mismatch on composition modulation has been assessed by introducing changes of composition in the InGaAs layers. In this case, a change of the propagation direction in the modulation is found.
Langmuir : the ACS journal of surfaces and colloids, Jan 5, 2018
Colloidal nanocrystals (NCs) compete with molecular catalysts in the field of homogenous catalysi... more Colloidal nanocrystals (NCs) compete with molecular catalysts in the field of homogenous catalysis, offering easier recyclability and a number of potentially advantageous functionalities, such as tunable band gaps, plasmonic properties, or a magnetic moment. Using high-throughput printing technologies, colloidal NCs can also be supported onto substrates to produce cost-effective electronic, optoelectronic, electrocatalytic, and sensing devices. For both catalytic and technological application, NC surface chemistry and supracrystal organization are key parameters determining final performance. Here, we study the influence of the surface ligands and the NC organization on the catalytic properties of InS, both as a colloid and as a supported layer. As a colloid, NCs stabilized by inorganic ligands show the highest photocatalytic activities, which we associate with their large and more accessible surfaces. On the other hand, when NCs are supported on a substrate, their organization beco...
ACS Applied Materials & Interfaces
Nanoscale research letters, 2017
Recently, colored H-doped TiO2 (H-TiO2) has demonstrated enhanced photoelectrochemical (PEC) perf... more Recently, colored H-doped TiO2 (H-TiO2) has demonstrated enhanced photoelectrochemical (PEC) performance due to its unique crystalline core-disordered shell nanostructures and consequent enhanced conduction behaviors between the core-shell homo-interfaces. Although various hydrogenation approaches to obtain H-TiO2 have been developed, such as high temperature hydrogen furnace tube annealing, high pressure hydrogen annealing, hydrogen-plasma assisted reaction, aluminum reduction and electrochemical reduction etc., there is still a lack of a hydrogenation approach in a controlled manner where all processing parameters (temperature, time and hydrogen flux) were precisely controlled in order to improve the PEC performance of H-TiO2 and understand the physical insight of enhanced PEC performance. Here, we report for the first time a controlled and local rapid thermal annealing (RTA) approach to prepare hydrogenated core-shell H-TiO2 nanorods grown on F:SnO2 (FTO) substrate in order to ad...
Nano letters, Aug 8, 2016
The physicochemical properties used in numerous advanced nanostructured devices are directly cont... more The physicochemical properties used in numerous advanced nanostructured devices are directly controlled by the oxidation states of their constituents. In this work we combine electron energy-loss spectroscopy, blind source separation, and computed tomography to reconstruct in three dimensions the distribution of Fe(2+) and Fe(3+) ions in a FeO/Fe3O4 core/shell cube-shaped nanoparticle with nanometric resolution. The results highlight the sharpness of the interface between both oxides and provide an average shell thickness, core volume, and average cube edge length measurements in agreement with the magnetic characterization of the sample.
Journal of Vacuum Science Technology B Microelectronics and Nanometer Structures, 1997
ABSTRACT In this work, we present a correlation between the morphological characterization of Iny... more ABSTRACT In this work, we present a correlation between the morphological characterization of InyAl1-yAs/InxGa1-xAs heterostructures grown on InP substrates for high electron mobility transistors (HEMTs) applications as determined by transmission electron microscopy, and the electrical behavior of the two-dimensional electron gas (2DEG) confined in the InGaAs channel. Our main goal is to analyze the origin of the low and anisotropic values of 2DEG Hall mobilities, discussing the effect of the density and asymmetric distribution of stacking faults and the surface undulation induced by a three-dimensional (3D) growth mode, depending on the growth temperature (Tg) and thickness (tw) of the InxGa1-xAs well. Our results have shown that a high mobility for a matched channel is obtained if the In0.53Ga0.47As layer is grown at 530 °C. Lower temperatures reduce the mobility values and lead to higher mobilities for [11¯0] due to the surface corrugation along [110] induced by lateral decomposition of the InGaAs at low growth temperatures. For HEMT structures with strained In0.75Ga0.25As channels grown at 530 °C, within the range of the well thickness considered (5–10 nm), Hall mobilities are also more influenced by the surface roughness than by fault distribution. However, in this case, the observed roughness is not driven by alloy decomposition but by a strain-induced 3D growth mode. © 1997 American Vacuum Society.
Microscopy and microanalysis : the official journal of Microscopy Society of America, Microbeam Analysis Society, Microscopical Society of Canada, Jan 12, 2016
In the present work, the dielectric response of III-nitride semiconductors is studied using densi... more In the present work, the dielectric response of III-nitride semiconductors is studied using density functional theory (DFT) band structure calculations. The aim of this study is to improve our understanding of the features in the low-loss electron energy-loss spectra of ternary alloys, but the results are also relevant to optical and UV spectroscopy results. In addition, the dependence of the most remarkable features with composition is tested, i.e. applying Vegard's law to band gap and plasmon energy. For this purpose, three wurtzite ternary alloys, from the combination of binaries AlN, GaN, and InN, were simulated through a wide compositional range (i.e., Al x Ga1-x N, In x Al1-x N, and In x Ga1-x N, with x=[0,1]). For this DFT calculations, the standard tools found in Wien2k software were used. In order to improve the band structure description of these semiconductor compounds, the modified Becke-Johnson exchange-correlation potential was also used. Results from these calcula...
Crystal Growth Design, 2009
Investigations on shape and chemical composition of one-dimensional magnetite nanostructures grow... more Investigations on shape and chemical composition of one-dimensional magnetite nanostructures grown by a catalyst-assisted vapor phase procedure are reported. Intrinsic crystal chemistry (preferred growth of most stable surfaces) could be modulated by seeding the magnetite ...
Springer Proceedings in Physics, 2008
ABSTRACT
ACS Applied Materials & Interfaces, 2015
(001)-Epitaxial La2WO6 (LWO) thin films are grown by pulsed laser deposition on (001)-oriented Sr... more (001)-Epitaxial La2WO6 (LWO) thin films are grown by pulsed laser deposition on (001)-oriented SrTiO3 (STO) substrates. The α-phase (high-temperature phase in bulk) is successfully stabilized with an orthorhombic structure (a = 16.585(1) Å, b = 5.717(2) Å, c = 8.865(5) Å). X-ray-diffraction pole-figure measurements suggest that crystallographic relationships between the film and substrate are [100]LWO ∥ [110]STO, [010]LWO ∥ [11̅0]STO and [001]LWO ∥ [001]STO. From optical properties, investigated by spectroscopic ellipsometry, we extract a refractive-index value around 2 (at 500 nm) along with the presence of two absorption bands situated, respectively at 3.07 and 6.32 eV. Ferroelectricity is evidenced as well on macroscale (standard polarization measurements) as on nanoscale, calling for experiments based on piezo-response force-microscopy, and confirmed with in situ scanning-and-tunneling measurements performed with a transmission electron microscope. This work highlights the ferroelectric behavior, at room temperature, in high-temperature LWO phase when stabilized in thin film and opens the way to new functional oxide thin films dedicated to advanced electronic devices.
Chemistry of Materials, 2015
2009 Spanish Conference on Electron Devices, 2009
(S) TEM tomography is used as a complementary tool to characterize AlAs-GaAs coaxial nanowires. T... more (S) TEM tomography is used as a complementary tool to characterize AlAs-GaAs coaxial nanowires. These nanostructures have been grown on two different GaAs substrate orientations using molecular-beam epitaxy (MBE). The results show that quantum wells synthesized on nanowires grown on different substrate orientations present different morphology, which induces changes on their photoluminescence properties.
Thin Solid Films, 2000
MgF2 is a current material for the optical applications in the UV and deep UV range. Nevertheless... more MgF2 is a current material for the optical applications in the UV and deep UV range. Nevertheless, modern applications still require improvement of the optical and structural quality of the deposited layers. In the present work, the composition and microstructure of MgF2 single layers grown on Si [100] substrate by physical vapour deposition (PVD) and ion beam sputtering (IBS) processes,
The Journal of Physical Chemistry C, 2012
ABSTRACT Microwave-assisted chemistry is becoming very attractive in all areas of synthetic chemi... more ABSTRACT Microwave-assisted chemistry is becoming very attractive in all areas of synthetic chemistry; it is fast, easy to operate, efficient in terms of energy consumption and environmentally friendly. However, a quantitative assessment of this chemical procedure with respect to other widely used chemical routes is lacking. Focusing in the preparation of iron oxide nanoparticles of comparable sizes, we have analyzed the performance of microwave-assisted synthesized nanoparticles compared to those obtained by the widespread thermal decomposition process of metal complexes. On the basis of a multidisciplinary experimental approach, we have unveiled that microwave-synthesized nanoparticles exhibit a surface reactivity significantly smaller than their thermal decomposition counterparts. We ascribe such dissimilarities to the different configurations of crystallographic faceting planes resulting from the particularities of both synthesis routes. We also show that the microwave route allows a direct stabilization of the particles in organic or aqueous media by using either steric or electrostatic stabilizers. A simplified life cycle analysis, as a preliminary framework toward nanoparticles eco-design, shows also a cost-effective positive balance for the microwave synthesis. Our results are of relevance for a broad range of applications including health, information storage, environmental remediation, sensors, or catalysis.
physica status solidi (a), 2003
ABSTRACT The influence of different technological parameters on the development of compositional ... more ABSTRACT The influence of different technological parameters on the development of compositional and morphological instabilities in InAlAs and InGaAs layers grown on InP substrates is studied in the present work by transmission electron microscopy (TEM). Results show that substrate misorientation plays a decisive role in the decomposition of strained layers. It is illustrated that the modulation of composition due to the layer morphological instability is a thermally activated process. The influence of lattice mismatch on composition modulation has been assessed by introducing changes of composition in the InGaAs layers. In this case, a change of the propagation direction in the modulation is found.